WO1998006273A1

WO1998006273A1 - Process and apparatus for field dicing/disinfecting produce and bulk bagging/cooling for extended shelf life

Info

Publication number: WO1998006273A1
Application number: PCT/US1997/013631
Authority: WO
Inventors: Rick L. Antle; Lawrence L. Ingram; Leonard J. Batti; Gurmail S. Mudahar; Paul A. DeGRANDPRE; Robert V. Antle
Original assignee: Tanimura & Antle, Inc.
Priority date: 1996-08-09
Filing date: 1997-08-04
Publication date: 1998-02-19
Also published as: EP0944330A1; EP0944330A4; AU3905997A

Abstract

A method and apparatus for field harvesting, coring, trimming, disinfecting, dicing, bagging and cooling produce, such as iceberg lettuce, comprising applying an antimicrobial disinfectant and lubricant solution to the internal mechanism of a cutter mechanism (109) mounted on the aft end of a self-propelled harvester vehicle. The antimicrobial is preferably a hypochlorite solution providing from 60 to about 700 ppm, preferably 80-300 ppm, of free chlorine in quantities sufficient to provide approximately 50 ppm of free chlorine in the run off from the cut produce after processing. Mounted on the aft end of the harvester vehicle platform is a pair of lateral conveyors (107) which feed harvested produce to the cutter, either directly or indirectly via a pair of elevator conveyors (108), a cutter mechanism, a cut produce transfer elevator (112) which lifts the cut produce pieces to a packing station comprising a hopper with bag lined toes or bins placed thereunder. Optionally, a spray of antimicrobial solution can be applied either to the produce coming on the lateral conveyors to the cutter, and/or the cut produce on the delivery elevator. The application of controlled concentrations and amounts of antimicrobial solution to the cutter elements during cutting, typically on the order of 50-120 gph, and preferably from 60-90 gph, results in a reduction in Total Aerobic Plate Count by over 80 %, and typically over 95 %.

Description

TITLE: PROCESS AND APPARATUS FOR FIELD DICING/DISINFECTING PRODUCE AND BULK BAGGING/COOLING FOR EXTENDED SHELF LIFE

DESCRIPTION CROSS-REFERENCE TO RELATED APPLICATIONS:

This is a Regular patent application arising out of our Provisional application serial Number 60/023,620 filed August 9, 1996, for "Process and Apparatus for Field Slicing and Disinfecting Head Type produce, Such as iceberg Lettuce", priority of which is claimed under 35 U.S C §§ 111(a)

TECHNICAL FIELD:

The invention relates to field harvesting and packaging, more particularly to a method for harvesting field crops, principally produce, comprising a field slicer/dicer and disinfection system and method for prepackaging and cooling the cut produce in bins which extends the total shelf life to on the order of 27 days for cut produce sold as a precut processed item While the examples herein are directed particularly to lettuce, endive, cabbage, celery, spinach, broccoli, cauliflower and the like, the principles of the process are applicable to other produce The system of the invention comprises a harvester having empty- and full-bin transfer means on the deck thereof and a special conveyor/dicer assembly at the aft end which includes a pair of laterally extending conveyors, a longitudinally-aligned, inclined loading elevator, a produce cutter, a disinfectant spray system, and a large bin bagging system The method and apparatus optionally includes a densifying or other packaging assembly including controlled atmosphere packaging equipment

BACKGROUND ART Consumer demand for convenience-type fresh prepackaged salads and prepared greens suitable for the rapid preparation of salads has expanded food service & retail store sales volume and resulted in a significant impact on the produce trade The supply problem is exacerbated in that the cut produce tends to spoil more quickly than whole leaf or head produce The single most important factor to insuring good quality in both whole and processed produce is the integrity of the "cold chain" from pre-cooling at the growing site, in-transit temperature control and warehousing, and in-store temperature control This -cold chain-, requirement while proving merely adequate, means that each grower or processor must produce a product that will survive in the current cold chain environment TO do so the producer/processor must very carefully adhere to strict processing protocols within a pristine environment, use appropriate packaging materials and anticipate on-coming product quality problems in spite of current levels of care in sanitation and packaging, there are still occurences of significant reduction in the shelf life of cut produce as compared to whole products Even if the "abuse" will significantly adversely affect cut produce more than whole produce. Yield and shelf life are interrelated, under current harvesting and processing techniques for a 5-7 day shelf life of tender product, the yield is as high as 70%. For 14-17 day shelf life the yield is 60% (or 40% loss). For tougher, older, more dense lettuce, the yield may be as low as 10% for 14-17 day shelf life dating. Shelf life is properly dated from day of harvest, although it may also be dated from day of completion of in-plant processing, usually within about 2-3 days after harvest at a source - located plant and up to 10 days for a plant located across the continent. As used in this application, the term "shelf life" is the practical saleable life measured beginning with harvest and ending with the manufacturers "best if used by- date, A key aspect to present techniques of processing is to keep the produce cool from in plant processing to the store shelves. The ideal range is from 34-38° F. spoilage of leafy vegetables occurs as a result of senescence, microbial decay, and oxidation reactions accelerated by latex which oozes out the lettuce butt (cut end of the core) and ribs, spoilage further accelerates as a result of temperature abuse. At the time of cutting, some loss of cellular integrity with a consequential dissipation of cellular fluids can occur. Handling damage results in torn and disrupted cells leading to enzymatic and microbial degradation of the cut produce. For example, it is common practice in iceberg lettuce harvesting for the crew to cut head lettuce prior to the arrival of the harvester. Prolonged storage times, particularly when there are general temperature abuses and attendant interruptions or breaks in the integrity of the "cold chain", also leads to the onset of senescence and anaerobic respiration. Accordingly, an apparatus and method is needed to increase the yield, throughput and shelf life of cut produce, such as cut lettuce, to satisfy the demand for prepackaged cut produce and pre-prepared salads, while minimizing the onset of spoilage and discoloration, or giving rise to potential microbial contamination of the product.

The present state of the produce field cutting art is described in Hougham, U.S. 5,316,778, and Cayton, U.S. 4,168,597. Hougham describes a method for processing common varieties of leafy vegetables whereby harvested produce is handled manually. The key step in Hougham is that the lettuce leaves are torn away from the residual core, leaving some of the core material on the stem of the leaf, it is said that this leads to less lettuce juice (latex), as the tearing is described as occurring along cell boundaries, as compared to cutting, which severs randomly through cells, once the leaves have been torn off by hand, the whole leaves are sprayed with an anti-microbial solution of water and chlorine. After spraying, the leaves are transferred to a refrigerated van for transport to the packaging facility wherein they are again washed, dried, packaged into plastic bags and cartons, and stored at a temperature of between 32-45° F until ready to ship.

The Hougham process is intended for leafy produce, and is not appropriate for other head produce such as iceberg lettuce, cabbage, radicchio, etc, or cauliflower, broccoli, and the like where the edible portion is a flower bud. Further, the process of Hougham is not an improvement in the rapid production of pre-packaged salads in that the whole leaves of lettuce torn by hand from the stem are intended to be sold whole and not in bite size, ready to eat form. Finally, the process as taught by Hougham is labor Intensive as it must be performed manually by cutting and leaf removal crews. These crews must painstakingly tear each leaf from the core, being careful to not bruise or otherwise damage the leaf. The leaves are left whole (i.e., not further reduced in size⁾ for a downstream sorting step. This process is inconsistent with the market need for higher production or throughput, In that the manual operation introduces a bottleneck in the process flow, as well as incurring additional labor costs. Further, as detailed more below, it introduces a significant source of bacterial contamination during the extensive manual handling. Thus, the final product is significantly more expensive to the consumer, it is also inconsistent with the market demand for uncontaminated pre-packaged salads in that the leaves are left intact; a size unsuitable for pre-prepared single serving salad consumption. Prior art in field harvesters include towed, tractor mounted or self-propelled flatbed vehicles which incorporate or operate in tandem with tractor-towed trailers on which bins or totes are transported through the field. The harvester typically has a pair of lateral, boom mounted waist high conveyors which together span 400-800 inches or 10-20 "beds" of produce. Workers usually one per furrow cut the produce from both the row to the left and to the right. The worker trails the harvester, cuts each head of lettuce at its root, peels off the wrapper leaves and places the head on to the conveyor. The lateral boom conveyor transfers the cut produce onto an attached elevator conveyor which lifts and discharges the cut produce in "free fall" into the trailer mounted bins or totes. When the bins on the trailer are full the trailer^'s) are transported to a nearby processing plant or a shipping facility for cooling and shipment to a distant forward processing plant. The bins are typically large containers that hold 800-1000 lbs. of head lettuce, but may be somewhat smaller 400-600lb capacity of size on the order of 4' x 3' x 2.5'.

With respect to lettuce harvesters which pack core-in head lettuce in cartons, with the lettuce being either unwrapped or wrapped, such harvesters typically have two booms pivoted to the rear corners of the vehicle which swing from an inboard stowed position to a laterally extended harvesting position so that they extend transverse to the long axis of the harvester vehicle. The booms ordinarily have three passive tiers. The worker on the platform sets up an empty box and places a plastic liner in it. The box (approximately 23.25" long, 15.25" wide, and 10.375" high) typically holds 24 heads of lettuce, weighing a total of approximately 40 lbs. The box is then placed by the worker on the top tier of the laterally extending boom, which tier comprises an open framework of an "L" configuration that is tilted at an angle like a magazine rack. The set up box with Its liner is then pushed laterally out toward the end of the top tier shelf by each successive empty box. This upper tier is the empty box tier. Workers (cutters) who cut the produce walk behind the harvester as it moves slowly down the rows. The lateral booms span a number of rows so there is typically one "cutter worker walking each furrow and cutting both the row to his left and to his right. The "cutter places the cut and trimmed (but not cored) head of lettuce on a boom-attached shelf the shelf and boom being generally orthogonal to each other and at a convenient position to the "packer who places the heads into the box. AS the packer needs a box, he reaches up to the upper tier, brings the box down to the lowest tier, which may be a continuous rack like the upper tier. Alternately, the lower tier may comprise a plurality of small platforms each the size of the box and having upstanding lips to help the box from sliding off. The packer trails the harvester, packing each cut and trimmed head of lettuce into the box by hand.

When the box is fuli of lettuce heads, the packer lifts the box up from the lower level to an intermediate or middle tier, which is typically a horizontal roller conveyor. The full box is pushed back toward the center of the harvester. The platform worker retrieves the box, closes it and stacks it on the forward end of the platform. This process (setting up the boxes; placing them on the upper tier; pushing them laterally out to the trailing workers or "packers"; moving the boxes down to the lower tier; filling them up and placing them on the middle tier conveyor; pushing them back to the center of the harvester; and retrieving and stacking them) continues until the harvester is loaded or the harvesting is completed. The filled boxes are placed on a transfer vehicle for transport to a shipping facility. That is, the harvester serves as a platform and a storage of knocked down empty boxes while the full boxes are placed on the transfer vehicle which periodically leaves the harvester to take its load to a cooling - shipping facility for shipping the boxed lettuce directly to market. If the lettuce is to be wrapped, the exact same machine and complement of workers is utilized. The additional steps are: the "cutter-, after cutting and trimming, places that head into a bag and then places that bagged lettuce onto the shelf referred to above. The "packer then closes the bag by twisting It to tighten the bag around the head before taping or otherwise sealing the bag before placing the "bagged/wrapped" head of lettuce into the box.

Typically, the bin-harvested lettuce heads are further processed In a local or regional processing plant. Additional damaged leaves are peeled off and the head is washed, bagged and kept cool for shipping. Alternately, after peel- off of damaged outer leaves, the head may be washed, cored and chopped or sliced into pieces. Thereafter, lettuce pieces are further washed, de-watered, dried, packaged and kept cool for shipping. in-plant processing including coring, trimming and chopping or slicing, results In significant inefficiencies and less than optimal yield and throughput of the cut produce. Transport of intact, whole heads of produce typically results in bruised or otherwise damaged produce and increases the spread of latex which creates an undesirable, nutrient-rich environment for microbial growth thus reducing the yield of quality product and conversely increasing the waste. Further, the transport of whole heads of produce is characterized by a significant amount of wasted space within the produce bin, since large spherically shaped objects do not pack efficiently. This contributes to a lower throughput of the produce. While more bins and transport trucks may be used to mitigate the throughput, these solutions increase transport and labor costs and logistic inefficiencies.

From the moment of cutting (the process of severing the lettuce head from its root in the field) to sale in the grocery store, speed, cooling and handling are critical. Time, heat and handling damage are major factors in lettuce spoilage. For example, a delay of several hours in the field under the blazing sun can result in significant spoilage as the bin laden platforms or trailers are not refrigerated, consequently, the prior view has been that any additional processing time or additional handling steps required to process the produce in the field would result in further degradation of product quality through spoilage.

During in-plant processing, there is typically a loss in yield (i.e. wastage or "shrink") of 30-40%. This wastage includes loss of core, wrapper leaves, cap leaves, and damaged or bruised heads. The reason for this change is that the wastage loss described occurs in the plant processing under the existing art.

By the process of the present invention, that in plant processing wastage loss drops to 5% from 30% to 40%.

A lettuce process and apparatus is described in cayton, U.S. 4,168,597. cayton teaches a field cutting apparatus and method whereby head lettuce is severed from the field, cut in an urschel Model H fixed blade impact cutter, and placed in a refrigerated container, cayton also teaches providing a self-contained mobile processing plant that can be transported to a site adjacent to the field for cleaning and packaging the shredded lettuce. The cut lettuce is brought from mid-field to the mobile field-side plant and cleaned, chilled and packed within the mobile plant. The Cayton field plant employed a 12' long water bath trough, which became warm in actual use and the cut product was centrifuged for drying. Centrifuge could not be secured adequately to its base, and accordingly did not work well. The cut lettuce from the bath was passed through a food pump which damaged the lettuce, cayton teaches use of a fine spray of chilled water having a preservative dissolved in the water. The already cut lettuce is then tumbled as it moves along a conveyor, cayton's apparatus requires a significant capital outlay, and the reference is silent on microbial assays, contamination, propagation and control, cayton's simultaneous chilling, washing and preserving step takes place in the mobile plant after harvesting and not on the harvester. This permits the product quality to degrade during harvesting operations until the preservative is applied later in the mobile processing plant. The Cayton system was also very slow, and it is not currently in commercial use. There have not been any definitive studies regarding key aspects of propagation and spread of microbial contamination either during field harvesting or in prior art proposals for mobile field processing plants. It seems intuitive that major initial sources of initial microbial contamination are environmental, including dirt, pests, birds, insects and airborne contamination. Field operations and automotive traffic near or in fields also contribute, and more and more so since fields are constantly encroached-on by urbanization. Poor harvest practices can also contribute, e.g., tracking dirt from prior harvested (cut) areas to uncut lettuce heads by workers and harvest vehicles. Further, harvest equipment is often characterized by a dark brownish film on surfaces contacted by the lettuce heads. This arises from the latex oozing from the cut stems. Latex provides an undesirable but rich nutrient source for microbial growth. This latex becomes spread over equipment operating surfaces and, indeed, can be flung or otherwise spread considerable distances during handling of heads. while the prior art discloses some cabbage and lettuce harvesters that first uproot the heads by spaced prongs or forks, and then cut the roots off before stowing the heads In containers, the prevailing practice is for manual field cutting with hand wielded knives. These knives also contact the hands and clothing of workers, cutters and box handlers typically do not wear gloves, so manual handling of each head is an additional source of initial microbial contamination and spread, it is a common practice in iceberg head lettuce harvesting for the field crew to "pre-cut" head lettuce, i.e., to commence the cutting prior to arrival of the harvester, while the harvester is turning around at the end of the row, or while it is down for maintenance or refueling. The worker cuts a head, takes the wrapper leaves off, turns the head butt up and lays the head on the cut root. Both the root and the stem ooze latex, and accordingly, dirt and latex get spread on the freshly-revealed inner leaves of the already cut heads. These are later picked up and tossed in the boxes. These common practices are inimical to prior proposals for field processing.

Most decontamination efforts are focused on in-plant procedures, particularly as they are controlled environments and subject to frequent health inspections and food handling code requirements, in the best plants, workers wear disposable gowns, gloves and hair nets. The lettuce heads and subsequently shredded or sliced lettuce pieces are washed extensively in water baths under carefully controlled conditions, including temperature, water flow rate, agitation, and disinfectant concentration. The typical disinfectant is chlorine, added as hypochlorite to at least some water baths with concentrations on the order of 50 ppm. in addition, prior to washing and/or slicing or shredding, the lettuce heads are inspected. Contaminated, bruised, dirty, burned, wilted or spoiled leaves are cut off and the core cut out, all by hand, split or cracked heads are typically rejected as contaminants or insects may have penetrated into the cracks. in the typical plant operation 1 - 2 gallons of chlorinated water are employed to wash each pound of product. The capital cost per processing plant of washing, conveying, drying and cooling apparatus runs into the tens of millions of dollars. The mass and physical size of this apparatus for cost effective throughput is enormous. Finally, the interiors of the plants are entirely cooled, typically to 34-38°F, even in areas when the outdoor temperatures exceed 110°F. All these factors make it impossible, practically speaking, to bring the plant to the field. The fields would become impassible if such quantities of wash water were disposed by release into the fields during harvesting. Accordingly, there is a need for a high-throughput, high yield, low wastage, low-cost process and apparatus for the production of high-quality uncontaminated cut produce suitable for immediate consumption by the consumer, and more particularly for a process that includes features to ameliorate discoloration and introduction and growth of bacterial contamination on the product during field cutting and handling, and which effectively extends the cold chain, all of which features result in a longer shelf life for the product while retaining excellent organoleptic properties.

DISCLOSURE OF INVENTION

It is among the objects and advantages of the invention to provide a high-throughput, high yield, low wastage, reduced handling, low-cost process and apparatus for the production of high-quality non- discolored, uncontaminated sliced/diced fresh raw produce such as lettuce, endive, cabbage, spinach, broccoli, celery, cauliflower and the like, suitable for salad consumption by the consumer. The apparatus and method of the invention also results In the additional advantages of a high harvest yield and an increased combined harvest and plant processing yield on the order of 32% or more. This increase is the result of reducing the number of handling steps and reducing time during which the cut produce is exposed to field conditions, including microbial contamination, heat, rain, dust and the like. This in turn results in a higher quality, throughput and yield of produce, with an increased shelf life up to 25 - 30 days for the cut produce, it is another object and advantage of the invention to analyze and discover the sources of pink discoloration, microbial contamination, and substantially eliminate the latex responsible for microbial propagation and spread during harvest and processing. it is another object and advantage of the invention to provide-disinfecting methods to effectively control microbial population and reduce the development of pink/brown discoloration on the cut produce pieces to a safe level as a new approach and key to successful field processing, it is another object and advantage of the invention to control discoloration of the cut product, it is another object and advantage of the invention to provide a method and apparatus for field densification of the cut produce product to up to about twice the initial cut density without introducing crushing of the product that could adversely affect shelf life. The provision of double bagging and vacuum cooling of the field diced/disinfected produce results in significantly extended shelf life of the cut produce while retaining organoleptic qualities, it is another object and advantage to minimize and control amounts of disinfectant at critical points in the processing required to control discoloration and to reduce microbial inoculation, growth and spread on the cut produce and to remove the cellular Juices (latex) inherent after coring and dicing. The invention is also not labor intensive and permits a reduction in crew resources.

The apparatus of this invention comprises a harvester having a deck with an optional tote and/or pallet/bin transfer mechanism thereon, optional lateral fold down platform extensions, a lateral conveyor system assembly, dicer/disinfectant system, a cut product conveyor and a bin/tote bag or retail-size packing station.

The methods of this invention stem in part from the counterintuitive discoveries that: 1). Coring in the field immediately after cutting (harvesting) but before dicing greatly reduces the amount of latex produced and introduced into the product processing stream. 2). The greatest site for microbial propagation is the cutter assembly wherein the harvested produce heads (e.g. iceberg lettuce) are diced; 3). The greatest microbial nutrient and discolorant compound source is the latex; 4). Microbial contamination is largely spread during the high speed mechanical action of the cutter elements, and 5). immediate bulk bagging and vacuum cooling of the field cut/disinfected produce pieces followed by cooling and closing or sealing the bag induces generation of a controlled modified atmosphere of high co₂ and low o₂, the result of which processing steps very substantially increases the yield and shelf life while retaining excellent organoleptic properties and retards discoloration. we have further discovered that there are relatively critical process steps and equipment areas to which the least amount of disinfectant need be applied to effectively remove latex, suppress microbial inoculation of cut edges, suppress microbial propagation and control microbial contamination to well within approved ranges for fresh food products.

Still further, we have discovered that spray or stream application of pH-adJusted aqueous hypochlorite solution in the range of below about 700 ppm, and preferably in the range of from about 60 to about 500 ppm of chlorine, depending on cutter type and environmental conditions, is effective in reducing, suppressing or delaying both discoloration and the development, inoculation, propagation and/or spreading of microbial contamination, at least pending transfer to local or regional processing plants for more conventional processing under controlled in-plant conditions as described above, we have discovered that microbial, principally bacterial, contamination, measured as numbers of colonies, can be effectively controlled during field cutting operations by use of controlled amounts of disinfectant solutions applied in the range of from about 1/10 to 1/ 00th the amount used during in-plant operations without imparting odor to the cut produce pieces, and this connection also controls discoloration in cut-piece product for extended shelf life on the order of 20-30 days. This reduces solution flow to the range of from about 5 to about 200 ml per pound of cut product, preferably 10 to 100 ml/lb as compared to 1 - 2 gal/lb produce for in-plant processing, in short the field- cut process of this invention is not water intensive, as compared to highly water intensive in-plant operations. The apparatus and methods of this invention successfully and effectively brings the following processes into the field, and out of the processing facility: coring; Disinfecting; Trimming; inspecting; and Slicing/Dicing, in addition, an early and critically located step of in-field disinfection provides the solution to pink/brown discoloration and suppression and control of microbial contamination that heretofore prevented adoption of prior art proposed field slicing or shredding processes. Finally, the bulk collection and bagging in bins followed by vacuum cooling within 2-3 hours followed by sealing the disinfected field-diced product begins the process of creating a low 0, (approximately .5% - 2%) high CO. ⁽-6-12%) modified atmosphere in the sealed bag. The result is substantially extended shelf life, on the order of 7-14 days to a total of 20-30 days, with retention of excellent organoleptic properties of the cut product.

As a result of the process and apparatus of this invention, the yield per acre of cut produce is significantly improved, on the order 30-35%, typically 32%, since the lettuce heads are cored and diced within moments of being harvested while still naturally transpiration cooled and before substantial quantities of latex ooze out to contaminate the surface of other produce. Further, handling and transportation losses are minimized or eliminated. Also eliminated are the added In-plant steps of removal of outer leaves that are browned, latex contaminated, wilted or otherwise damaged during waiting, handling and transportation. These otherwise good leaves are retained and contribute a total weight increase of around 32% to the end product. Because the coring, disinfecting, trimming and dicing are done in the field before any handling damage can occur, the end processing plant loss of yield (I.e. wastage) typically less than 5%. Further, the 32% Increase in yield is accompanied by a minimum 7 day increase in the amount of time the processor can either transfer or store the product without suffering any organoleptic or yield loss. By way of example, an acre typically yields about

36,000 pounds of whole head lettuce, in present commercial in-plant processing, the net yield is around 21, 600 lbs. of finished bagged cut lettuce, in contrast, in accord with the process of this invention, the net in-plant processing yield is 28,500 pounds, which Is nearly 132% of the prior process of cutting in-plant. Further, the 32% increase in yield is accompanied by minimum 7-day increase in the amount of time the processor can either transfer or store the product without suffering any organoleptic or yield loss.

The in-plant coring and accompanying handling and re-handling of whole produce is entirely eliminated. Application of the aqueous (hypochlorite) solution in the inventive process maintains or rehydrates the cut product during temporary storage in containers on the harvester vehicle bed and during transport to the plant for further processing and bagging, in-plant processing is reduced and speeded, in that reduced washing may be required, the coring, trimming, inspection and slicing operations are eliminated, and the drying, cooling and packaging (bagging) operations are simplified and/or speeded. Further, hydration can improve the efficacy of vacuum cooling.

The optional densification steps, accomplished by compression of partially filled bins or totes with a pressure plate which in its simplest form may be another tote, increase transportation efficiency by reducing the number of trips from the field to the plant. Moreover, thermal Increase (overheating⁾ loss due to longer dwell time in the totes is unexpectedly offset by the increased thermal stability due to humidificatlon and increase in tote mass. The tote mass increases from about 40-48 lbs for the typical uncompressed tote to about 50-80 lbs, preferably 55-65 lbs for the densified (compressed) tote (of typical inside dimensions 19" length X 22" width X 13" depth), where bins are used, they are typically 44"length x 36" width x 23 Vϊ" inner dimension and hold 400-500 lbs. of cut lettuce, or 560-700 lbs. of densified cut lettuce, a 40% increase. in an additional optional step, the undensified or densified totes or bins of cut lettuce or produce can be packed under a supplied modified atmosphere appropriate for the product (e.g., for lettuce, low 0₂, high co₂). For example, where the packaging film or window is selected, produce Item by item type, for desired relative o_/CO- transmission, the shelf life can be extended at least an additional 7 days without suffering any organoleptic or yield loss. in addition, it is an important and preferred step in the process of the invention to bin bag the cut produce in the field and then cool the cut produce within two hours of cutting and thereafter sealing the bag. This significantly assists in maximizing the microbial control via application of antimicrobial solution to cutter elements thereby removing latex and in extending the shelf life, upon sealing the bag after cooling, the lettuce continues to respire, and a controlled modified atmosphere low in 0- and high in CO- develops which assists in extending the shelf life. We presently prefer to use double bag of polyolefin in the bins, e.g. two 1-2 mil polyethylene film bags each having an OTR (Oxygen Transmission Rate) of 320-400 cc per 100 in² per 24 hrs, which results in a CO, level of within the range of 6-12% and an 0. level within the range of .5-2%. The double bagged bin of field cut disinfected lettuce weights approximately 800 lbs. After vacuum cooling, the bags are clinched shut, e.g. with a metal or plastic band to seal them against contamination during subsequent warehousing or transportation pending reprocessing at local, regional or distant processing plants. it is significant that the process of the invention essentially redefines the processing market, in that basic processing occurs in the field and processing plants become simply washing and bagging operations. The bricks and mortar costs are reduced and the major labor and handling costs are eliminated in these new style reprocessing plants, yet the shelf life is extended and the cut product is as good or better.

The harvester vehicle of the invention is typically a self-propelled vehicle having a rectangular main platform in which are mounted transfer mechanisms for moving full totes or bins from the aft to the forward end, and then onto the shuttle vehicles, in addition, the harvester vehicle includes two longitudinally extending side platforms, or "catwalks", which are pivotable from a horizontal working position to a raised vertical transport position. Alternately, the catwalks may be stowed for transport by sliding them into receiving slots or pockets underneath the harvester platform. The longitudinal side catwalks have an optional tote/bin conveyance means, typically rollers, wheels, slide rails, chain driven transfer tracks or the like, to permit workers to move empty totes or bins, previously unloaded from the shuttle truck and onto a forward portion of the catwalk, toward the back of the harvester vehicle where they are then moved laterally inward and placed on the harvester platform transport mechanism for loading. Ideally, the side catwalks are at least as wide as a single bin or tote. The forward portion of the catwalk receiving the empty totes may be an extension or "tongue" extending longitudinally forward of the harvester platform so as to partially extend along the sides of the docked shuttle vehicle to provide a lateral extension of the bed of the docked vehicle. The pair of laterally extending conveyor boom assemblies is pivotably mounted on the rear of the vehicle, typically somewhat inwardly of the left aft and right aft corners. Each boom is pivotable on a vertical shaft or axis from a stowed position in which the booms extend parallel to the center axis of the harvester vehicle while resting on the platform, to a laterally extended lowered position and are adjustable in working height from approximately knee height to waist height. These booms extend laterally from the aft end of the harvester vehicle across several rows, cutters trailing behind the moving harvester cut the produce (e.g., lettuce heads), peel and remove the outer wrapper leaves, optionally core the produce, and place the produce onto the powered conveyor belts to be conveyed laterally inwardly toward the center of the field dicer/harvester vehicle. At the inner end of the boom an optional, preferably short, inclined, transfer elevator conveyor lifts the produce heads and deposits them into the cutter hopper. Alternately, the produce may be discharged directly from the lateral conveyors into the dicer hopper.

The platform of the harvester may optionally include means for facilitating movement of heavy, loaded pallets of produce totes or bins, such means include chain driven transfer tracks, or other pallet/bin conveyance means such as rollers, wheels, slide rails and the like. The harvester may include means for docking with a transfer vehicle, in operation, a self-propelled, or towed, transfer vehicle, such as a truck or trailer, backs up and docks with the forward end of the harvester. The truck is then put into neutral and the harvester pushes the truck down the row. The truck contains on its flat bed a number of empty totes or bins. The side catwalks of the harvester are typically folded against the sides of the harvester for transport, and are extended outwardly during harvest thus extending the width of the harvester platform

The field harvester system of this invention may be tended by one or more shuttle or transfer vehicles, typically a flat bed truck having optional empty and full tote or bin transfer mechanisms on the bed thereof. The shuttle vehicles bring the empty totes or bins to the harvester vehicle, and transfer full totes or bins back to a local or regional processing facility. The self-propelled harvester of this invention includes an optional shuttle vehicle docking mechanism for engaging a bin-supply shuttle, once the shuttle vehicle is docked, empty produce totes or bins are either off-loaded or full totes or bins from the harvester may be on-loaded onto the vehicle.

The field cutter system of this invention comprises: a) a pair of adjustable lateral conveyors extending transversely from the rear of the harvester vehicle for moving Just-harvested produce (cut heads) to the harvester platform, and optional inclined elevator conveyors for feeding the cutter hopper; b) a cutter assembly mounted on or adjacent the aft end of the harvester deck for receiving and dicing the fresh cut produce heads into bite-size pieces (about 2" x 2") suitable for pre-packaged, immediately consumable salads; c) an inclined transfer elevator for moving the cut produce to a receiving station for packing (including densi ication compacting) into bins, totes or smaller containers; d) a disinfecting system comprising a disinfectant solution storage container mounted on the platform, a pump, and a plurality of strategically placed spray heads for application of disinfectant solution to the dicing/cutting apparatus internals or/and to the cut lettuce (produce); and e) a packing station with optional densification means, which is preferably a bin bagging system. A cable and boom system is used with the lateral conveyors to permit raising and pivoting the lateral conveyors to a second longitudinal position that is parallel to the sides of the harvester for road transport. The field workers, called "cutters", select (grade), cut (sever), core (remove the inner stem), and trim (remove wrapper and/or damaged cap leaves) the lettuce head before placing the head gently on the lateral conveyor, hen extended to its transverse harvest position, the conveyor employs hydraulically or electrically powered belts to transport the freshly harvested produce, inwardly toward the cutter assembly where they discharge into a cutter hopper, either directly or via a lateral, inclined elevator. Where a lateral, inclined produce elevator is used, its belt is modified with a plurality of flights, flanges or flaps running transversely to the longitudinal axis of the belt to prevent the produce from rolling back down the belt. Further, the belt may have side guards to prevent the uncut produce from rolling off of the belt. All belts are of food-grade quality as defined by federal, state, and local rules and regulations.

By way of definition, the reference to a "cutter" for, or -cutting" the, harvested produce, e.g. iceberg lettuce, Includes all apparatus and modes of separating the produce in pieces, other than by tearing, ripping or sawing, by relative movement of the produce with respect to a knife edge, and those terms are generic to "slicing" or "slicer and "chopping" or "chopper." The terms include the act of, or apparatus employing a knife edge in motion, including use of rotating thin discs having sharpened edges, and/or use of a stationary blade in which the produce is accelerated toward a fixed blade to impact cut lettuce. Thus, "cutting" and "cutter also includes both "slicing" and "chopping" processes and means in one apparatus, such as an Urschel Model H unit, in which the lettuce is first chopped by the head being impelled against a fixed blade, and the removed (chopped off) segment is further cross-cut orthogonally, first by a carousel (reciprocating knife) cutter, and then by a set (gang) of multiple parallel rotating thin discs. "Dicing" as used herein refers to multiple cuts, generally at oblique angles which can include orthogonal cuts, to produce the bite-sized pieces. Produce is diced in two or three dimensions. Thus, cutting and slicing are used interchangeably herein, with rotary thin blade dicing (multiple angle slicing) being preferred.

The dicer hopper feeds the produce into a cutter assembly whereby the produce is diced into the desired size and shape and antimicrobial treatment solution is introduced during the cutting operation. The preferred mode of cutting is slicing by means of rotatlonally "sliding" a very thin blade through the produce to provide a clean, well defined cutting or sectioning of the produce with a minimum of cellular damage or rupture, when we refer to the rotating blade passing through the produce, we mean relative motion, whether the thin blade is rotatably moved through the produce head, vice versa, or both are in motion, often in different axes, it is important to ensure that, in using fixed blade type cutters, where fibrous materials are being cut, such as celery, lettuce, cabbage, radicchio and the like, build up of fibrous materials on the blade edge is prevented. This build up can then cause blunt trauma and crushing of the celts, which can cause additional latex to be expressed during cutting.

Latex Is a very rich source of nutrients for undesired microbial growth, including various bacteria, fungi, and molds. By immediate field coring, the greatest latex reservoir is removed from the lettuce. The pink and brown discoloration results from oxidation of the phenolic compounds in the latex acted on by cellular enzymes, principally polyphenoloxidase, which produces pink and brown colored quinones. The immediate application of the disinfectant spray washes away latex expressed during the dicing or cutting, thus removing a principal source of this discoloration and microbial nutrients. in a preferred embodiment of the cutter assembly, the knives comprise at least one pair of a plurality of ganged, counter-rotating, interleaved, thin circular knife blades. Produce falling between the rotating knife blades is sliced into pieces having a width equal to the distance between blades. optionally, the sliced produced may be further sliced by a second, lower interleaved set of ganged knife blades. Depending on the alignment of the second pair of knives to the first set, the once-sliced produce may be diced (cross-sliced by orthogonal alignment) or julienned (cut in narrow strips by parallel alignment), A preferred dicer is a Backus Sormac multi-gang, counter rotating round blade slicer, or a rotating cage cutter. However, in another embodiment of the invention, the produce may be Initially cut by acceleration against a stationary blade and then cross-cut by other moving blades

(as in a commercially available urschel Model H lettuce cutter).

Once the produce has been diced while being treated with antimicrobial solution, it is discharged from the cutter assembly and deposited, either directly or via a transfer conveyor belt, onto an inclined elevator conveyor aligned parallel with the longitudinal axis of the harvester. The Inclined elevator conveyor is mounted at the aft end of the harvester platform and extends from below the cutter assembly, upwards and forwards to a receiving station. As in the lateral elevator, the longitudinally-aligned elevator comprises a food-grade belt having flights running transverse to the longitudinal axis of the elevator, as well as upturned sides. These keep the cut produce from sliding down or off the inclined belt, in addition, the belt Is perforated to permit excess antimicrobial solution and latex to effectively drain off the produce onto the ground, once the cut produce reaches the top of the belt, it is discharged into a tote chute which directs the cut produce into a single or multiple use bag (or nested pair of bags) or other container, supported in a one-way or reusable transport container. The totes are reusable, stackable bins of a size sufficient to accommodate a manually handleable quantity of cut produce, yet not so large as to be unwieldy, once the plastic bag is filled, it is closed, as by folding over the top of the bag, the full tote is moved and stacked on the back of the platform, and a succeeding empty tote is put in place at the packing station for filing. The plastic bags perform a variety of functions that contribute to the minimization of enzymatic browning and to the extension of shelf life of the cut produce. The plastic bags provide protection from dust and drying as the damp cut produce awaits transport from the harvester. By closing the bag to prevent infiltration of dust, the amount of in-plant washing can be reduced, typically speeding that process step. Further, the bags retain moisture for hydratlon of the cut pieces, preventing the loss of turgidity and the onset of wilt and cellular decomposition. Any off -gassing of residual chlorine or other disinfectant is also sealed in, further increasing the efficacy of the disinfectant. Finally, the on-going respiration of the shredded produce rapidly consumes oxygen within the plastic bag and increases the carbon dioxide level. Reduced oxygen level is helpful in retarding growth of aerobic bacteria and molds, as well as limiting the onset of enzymatic browning. The increased levels of carbon dioxide contribute to the anti-microbial effect of the disinfectant and retard the growth of bacteria, molds, and fungi. Another novel feature of the apparatus of this invention Is the disinfectant delivery system. The produce is sprayed with a disinfectant solution during cutting, and optionally after and/or before it has been cut. The two-fold purpose of spraying the produce with controlled quantities of a disinfectant is to significantly reduce the level of microbial inoculation and growth on the produce, and to rinse away a substantial portion of the cellular fluids, comprising latex and other nutrients for undesired microbial growth. The disinfectant flow can be adjusted in quantity to rinse off loose, cellular material from the produce, belts and knives. The cellular fluids are very sticky, coagulate quickly and adhere to surfaces, including smooth, polished stainless steel Interior surfaces of the cutter assembly, thus providing a rich growth medium to such surfaces. By Immediate (relative to time of cutting) and continuous spray of disinfectant solution on the cutter internal surfaces and the cut lettuce, even in the relatively small quantities discovered to be effective herein, the process of the invention inhibits latex adhesion and coagulation, removes nutrients and growth medium to retard the microbial growth and kills microbes. This results in a reduction in oxidative/enzymatic browning as described above and extends the shelf life of the cut produce. it should be understood that the term "spray" as used herein includes introduction of a stream of antimicrobial solution into the rapidly moving cutter mechanism. That high speed movement serves to break the stream up into fine droplets. However, conical or fan type sprays can be employed in the external areas of the cutter such as the input hopper or the cut product transport conveyors.

The antimicrobial solution may be any FDA approved, food grade ingestlble antimicrobial, we presently prefer to use an aqueous solution of sodium hypochlorite, NaOCI, and a citrate/phosphate buffer mixed in water to bring the pH in the range of from 6 to 7.5, preferably 6.5 to 7.0, and the free chlorine concentration to within the desired range of from about 80-600 ppm, preferably 80-300 ppm on the delivery side, but sufficient to leave about 50 ppm in the discharge. A convenient buffer that may be used is ORP buffer from Morgan callacher inc., Santa Fee springs, CA. The hypochlorite may be "AgChlor 310", a 12.5% concentrated hypochlorite solution from Dacco inc., a division of ELF Atochem. The pH should be kept above 5.5 as the hypochlorite degasses at a lower pH.

Beside hydration, an additional benefit of field cutting with the aqueous antimicrobial solution is that the additional moisture assists in subsequent vacuum cooling, vacuum cooling of the cut lettuce is very effective in cooling the product, but at the same time it reduces the moisture content of the product from to 2 to 3%. This can lead in some instances to dessication damage and poor appearance of the lettuce product. Thus, the fully hydrated product produced by the instant process permits fast cooling without dehydration. in regards to coagulation, the latex and other complex organic molecules that comprise the cellular fluids readily polymerize to a resinous, gummy composition which builds up and browns on the knives, associated cutting mechanism surfaces and belts, such buildup becomes a home for bacterial growth, which is transferred to the produce resulting in contamination. Thus, for example, it has been found that the highest bacterial count comes from swab samples at the lettuce cutters, as compared to elsewhere in processing operations. While not wishing to be bound by theory, we have come to believe that for this reason of cutter-induced bacterial contamination, of which the prior art was apparently not aware, prior proposals to field cut or shred lettuce have not been successful. Thus, this invention includes continuous spraying of cutter surfaces with a controlled concentration and quantity of disinfectant or antimicrobial solution to assist in removal of latex nutrients and/or suppress growth and transfer of bacteria.

While not required, it is preferred to provide a spray nozzle positioned over the lateral wing conveyors to wash away cellular discharge and debris off the conveyor belt and to control latex and other organic nutrient buildup and consequent establishment of microbes and pink/brown discoloration, it is also preferred but not required to have a second spray nozzle positioned to spray the produce (head lettuce, by way of example) as it enters the cutter hopper to facilitate entry into the cutter mechanism by a lubricating action. it is critical to position a fluid discharge nozzle outside or inside the cutter chamber which is directed toward the cutter mechanism, preferably at the knives. The nozzle delivers a continuous stream or spray of treatment solution on the cutter internals and the as-cut produce pieces to prevent or retard latex coagulation and organic buildup and bacterial inoculation of the cut produce.

Preferably, one or more additional spray nozzles are directed at the cut produce as it is discharged from the cutter assembly onto the longitudinally inclined elevator, midway up the elevator, and at the top of the elevator and/or in the packing chute or hopper. This spray system ensures that there is good coverage of the cut produce with the disinfectant spray to prior to packing in totes.

The cut produce is discharged from the top end of the inclined elevator into a produce hopper. The produce hopper receives the cut produce and acts as a surge or holding vessel for the cut produce that is being continually discharged into the hopper. The produce hopper enables the packing crew to remove full totes/bins and to position an empty tote in place without having to interrupt the continuous dicing operation. The totes or bins are lined with one or more breathable plastic liners, such as two separate 1-2 mil polyolefln bags. The liner material may be selected based on permeability to various gases, Including oxygen, carbon dioxide, chlorine, ozone, and water vapor. During loading of the tote, the produce may be densified by compression, in one or more stages, but not to the extent the produce is bruised or damaged. By compressing packing, void volume is substantially reduced as compared to loose cut lettuce, once full, the plastic lining is closed (folded over) to keep out dust and dirt, optimally the bag may be sealed with a self-generating or externally supplied modified atmosphere environment therein, on-going out-gassing of chlorine (or other gas such as iodine, bromine, or ozone) as defined by the composition of the disinfectant solution) is trapped in the plastic enclosure, thus furthering the disinfecting process for several more hours until the produce is repackaged, or else the gas has transpired through the plastic. An additional benefit of the plastic enclosure is that the cut produce is kept hydrated by the water vapor and aerobic respiration is reduced as the oxygen is used up, and carbon dioxide levels increase. Using plastic liner retains the anti-microbial gas and water vapor constituents and permits development of a modified, low o₂/high CO, atmosphere produced in the bag by the continued metabolism of the cut lettuce.

The net result of the process and apparatus of this invention Is that the microbial growth, reflected as Total APC on a per pound basis, is retarded so that even 10 days after field cutting, the Total APC is lower than normal for fresh harvested unprocessed head lettuce, typically even after the wrapper leaves are removed from the fresh harvested head lettuce and even less than the total APC present in 10-day old consumer size (e.g., 1-5 lb) bags of cut lettuce produced in current in-plant processing facility. Packing the cut produce in plastic bags in the tote, and subsequent closure of the bags prevents dust and dirt from infiltrating the cut product In the bag during transport to the local or regional plant. Handling damage is reduced and processing is speeded, resulting in a fresher product. in conjunction with the bulk bagging, vacuum cooling and the controlled atmosphere that develops in the sealed bags, the shelf life can be extended on the order of an additional 10 days.

BRIEF DESCRIPTION OF DRAWINCS:

The Invention is described in connection with the drawings in which: Figure 1 is an illustrated flow sheet of the process of the invention;

Figure 2 is a left rear perspective view of a dicer/harvester system according to the present invention;

Figure 3 is a partial side elevation of the dicer/harvester system of Fig. 2;

Figure 4 is a rear elevation view of a dicer harvester system of Fig. 2 employing sprayer-modified urschel type impact cutter;

Figure 5 is a rear elevation view of an alternative, double gang rotating blade dicer mechanism for the harvester system of the present invention;

Figure 6 is a side elevational view of the dicer assembly of Fig. 5;

Figure 6A is a top plan view of the modified Urschel cutter of Fig. ft showing the placement of fluid delivery nozzles in preferred and several alternative positions;

Figures 7 and 8 are bar graphs of a comparative field cut test showing 99+% reduction in microbial contamination by use of hypochlorite treatment solution introduced Into the cutter chamber as compared to untreated cutters, with Fig. 7 reporting Total Aerobic Plate count, and Fig. 8 reporting Coliform bacteria, including e. coli; Figure 9 is a graph of another field cut test showing reduction In Total APC as a function of free chlorine in the treatment solution;

Figure 10 is a graph of another field cut test showing reduction in Total APC as a function of both free chlorine in the treatment solution and solution delivery rates to the cutter mechanism;

Figure 11 is a nomograph of percent reduction of total APC as a function of solution flow rate in gph and the log of free chlorine;

Figure 12 is a 3-dimensional graph of percent APC reduction vs antimicrobial solution flow rate (In gph) vs free chlorine, (in ppm) in the solution delivered to the cutter; and

Figure 13 is a schematic flow sheet of the optional densification process.

DETAILED DESCRIPTION OF THE BEST MODE OF CARRYINC OUT THE INVENTION:

The following detailed description illustrates the invention by way of example, not by way of limitation of the principles of the invention. This description will clearly enable one skilled in the art to make and use the invention, and described several embodiments, adaptations, variations, alternatives and uses of the invention, including what we presently believe is the best mode of carrying out the invention. Figure 1 is an illustrated flow sheet of the over all process 100 of this invention, including the in- Field steps 150 and in-Plant steps 200. Head lettuce 101 growing in field 102 is harvested (cut) and trimmed (wrapper leaves removed) by hand 103, and is cored 104, typically also by hand. The core 105 and wrapper leaves 106 are discarded in the field. The harvested/cored lettuce heads 107 are placed on conveyor 108 which discharges them into the cutter 109 which Is described in more detail below. Disinfectant spray 110 is applied to the cutter internals, and the cut lettuce pieces 111 are transported by discharge conveyor 112 to a large bin 113 typically having single or multiple plastic liner bags 114 therein. The bag⁽s) Is/are closed but not sealed at 115. Not shown is an Intermediate, optional, step of denslfication which is shown below in Figure 13, and which would occur at stage 116 of Figure 1. This concludes the in-Field Operations 150.

The bin 113 containing the full bag(s) 114 of diced lettuce having a weight on the order of 400-500 lbs. is then transported 117 within 1-5 hrs, preferably 1-3 hrs, to a local or nearby regional cooling facility 200 In which the bag of field-diced disinfected lettuce is vacuum cooled 201. Note that while the bag can remain closed, it will permit degassing and removal of water vapor through the unsealed top of the bag 202. After release of the vacuum 203, the bag is clinched closed with a metal or plastic band 204, or it may optionally be otherwise heat or tape sealed. The now-completed bulk bagged chopped lettuce product 205 remains refrigerated 206 during shipment or other storage 207.

At this stage, the large bulk bag 205 containing, typically, in excess of 400 lbs. of the field/diced/disinfected/cooled lettuce product in the sealed bag is a commercial product, it can be retained in that condition for up to about 10-14 days 208 before further processing. During this time, it can be shipped long distances to regional repackaging plants for processing 220. These plants are relatively low capital operations, not requiring head inspection, coring, trimming, slicing, and, optionally, vacuum cooling facilities, equipment or personnel. This transforms what were formerly processing plants into repackaging plants, in which the operations in the plant 220 comprise receiving the cooled bulk bagged field cut and disinfected lettuce 205, opening the bags and re-washing the lettuce 209, de-watering and drying the lettuce 210 and re-packaging It 211 Into consumer sizes, such as 1 to 5 pound bags, or portion packing it for fast food restaurants or in individual single serve salads along with condiments, croutons, meat etc. shown In Figure 1, the shelf life out of the re-packaging operations 220 on to the store shelves 225 is on the order of 14 to 20 days 226. Referring now to the drawings, Fig. 2 shows the field dicer harvester 10 of this invention in partial perspective. A truck or trailer transfer vehicle (not shown) containing a load of empty totes/bins 12 is optionally backed up to the forward end of the field dicer (to the left) and docked so that the empty totes 12 may be transferred to the deck 14. The field dicer deck 14 may include one or more optional lateral side catwalks 16 on which to queue empty totes 12. These catwalks 16 may also include conveyor rollers 26, wheels, or other means to facilitate the moving of pallets or empty totes to the rear of the field dicer. Ideally, the width of each catwalk is the approximately the same as the totes.

The deck may also include an optional tote/pallet transport means (not shown, but preferably a chain pull drive, slide rails, a conveyor belt or conveyor rollers) mounted in the deck surface on which the totes 12 may be moved forwards and backwards relatively easily for positioning beneath the packing hopper 60, and for moving loaded totes back onto the transfer truck or trailer. Mounted at the rear of the harvester are: a) a cutting (dicing) assembly 18; b) a harvested and cut produce conveyor system 20; c) a disinfectant delivery system 22; and d) a packaging station 24. The disinfectant delivery system 22 includes antimicrobial solution tank 64, pump 66, and lines (not shown) to nozzles 62.

The produce conveyor system 20 includes: a) at least one, and preferably two lateral conveyors 28; b) two optional inclined lateral transfer conveyors SO, each having a food-grade belt 32 with rigid flights 34 or fingers, flaps or flanges to prevent the vegetables 46 being elevated from rolling back or off of the belt 32; and o a longitudinally-oriented, inclined cut-produce elevator conveyor 48 for moving the cut produce into the totes 12. The elevator conveyor 48 has a perforated, food-grade, belt 36 with rigid flights 34 or flanges to prevent the produce from rolling down the conveyor 48.

The two lateral conveyors 28 are transverse to the longitudinal axis of the field dicer to permit the harvesting of a large number of rows with each pass of the harvester field dicer 10. The lateral conveyors are pivotably mounted on header frame 70 and are raised by hydraulic rams 38 to permit them to be folded towards the sides of the field dicer 10 to facilitate road transport. The outboard ends of the lateral conveyors 28 may be raised and lowered by the rams 50 via cables 52 having one end attached to the outboard end thereof. The other end of the hydraulic cylinder 50 is attached to a portion of the harvest platform rear header framework 70 proximal to the inboard end of the lateral conveyor 28. This height adjustment permits positioning the lateral conveyor belts 32 at a vertical height above the ground that facilitates the harvesting of the vegetable 46 that is being picked.

Operation is described by reference to Figs. 1-5. Produce are picked/cut by a field crew trailing the field dicer 10. The outer wrapper leaves of leafy produce are removed, and the produce is preferably cored. The produce is deposited onto the moving lateral conveyor belts 28 and are directed towards the center of the field dicer 10. once the produce has reached the inboard end of the lateral conveyor belts 28, they are either directly discharged into a hopper 54 of the cutting assembly 18, or elevated by the lateral elevator conveyors 30 where they are then deposited into the hopper 54 of cutter 18, or 18a. once the produce has been cut in cutter chamber 40, it exits the cutter discharge chute 42 and it is deposited onto the inclined cut produce elevator conveyor 48 where the produce is lifted to an elevated discharge point 56 from which it is collected in a cut produce package hopper 58. Finally, the produced is discharged from the bottom chute 60 of the cut produce hopper into plastic bag-lined totes or bins 12. optionally, the cut produce can be directly packed in the field (or in-plant without further washing) in consumer packages, such as 1 to 5 lb. poly bags, in which case the bagged produce can go directly to market, see 227 in Fig. 1.

Fig. 4 shows a preferred side discharge cutter assembly 18 and the offset longitudinally-oriented elevator conveyor 48 positioned to receive the cut produce being discharged from the side 42 of the slicing assembly 18. The solution tank 64 and pump 66 are shown to the left on platform 14. An example of a side discharge cutter assembly 18 is an Urschel Model H, a commercially available cutter available from Urschel Laboratories, inc., Valparaiso, Indiana. Fig. 6A shows the Internal mechanism of this type of commercially available cutter with the location of the nozzle modifications thereto in accord with this invention. Fig. 5 shows an alternate preferred, down-discharge cutter assembly 18a, resulting in the longitudinally-oriented elevator conveyor 48 being centrally positioned so as to receive the cut produce that is being discharged from the bottom of the cutter assembly 18. An example of a down discharge cutter is illustrated in more detail in Fig. 6 which shows a double gang, rotating blade assembly that slices, rather than chops the lettuce, and that discharges the cut produce downwardly.

Although both Figs. 4 and 5 show lateral transfer elevators 30 being used to transfer the produce from the lateral conveyor 28 to the slicer hoppers 54, an alternate embodiment is to feed the cutter hoppers directly from the discharge end of the lateral conveyors 28. Figs. 2 - 6 also show a plurality of nozzles 62 delivering antimicrobial fluid in a stream or spray to the cutter apparatus in chamber 40, and optimally to the hopper 54, the discharge chute 42, the elevator conveyors 30, 48 and/or the packing hoppers 58 . An aqueous solution of sodium hypochlorite is the preferred disinfectant, although other halogenated solutions, such as sodium bromide or sodium iodide, or ozonated solutions may be used. in the example of Figs. 2 and 4 can be seen a tank 64 and a pump 66 for holding and delivering the aqueous treatment solution to the nozzles 62. supply tubing and support means for the nozzles 62 are partially omitted for the sake of clarity.

Produce enters the hopper 54 and enters the cutting chamber 40 where it is cut (diced) to the desired size. The selection of the type of cutter assembly 18 or 18a will determine whether the longitudinally aligned elevator conveyor 48 is to be centered coincident to the centerline of the field cutter platform (in the case of a downward discharging cutter assembly 18), or offset to one side (as in the case of a side-discharge cutter assembly 18a). The produce is transported up the elevator conveyor 48 and discharged into the cut produce hopper 54, from which it Is packaged into the plastic bag lined produce totes 12. Figs. 4 and 5 also show the alternative embodiments in which nozzles spray the produce as it enters the hopper 54, as the cut produce exits the cutter assembly 18, and at various points on the elevator conveyor 48.

AS best seen in Figs. 6 and 6A, one or more spray nozzles 82 are provided to introduce a spray or stream into the cutting chamber 40 to coat the rotary blades 74a, 74b (Fig. 6) or fixed knife blade 65, cross cutter reel 84 and circular blades 76 (Fig. 6A), so as to assist in washing away any cellular fluids before they have a chance to build up and prevent not only contamination, but also a quality hazard by adversely affecting the ability of the knife blades to provide a clean slice or cut with minimal tearing or disruption of cells.

The produce is shown being discharged by elevator 48 Into the hopper 58 of the cutter assembly 18 in Fig. 4. optionally, some disinfectant solution is continuously sprayed into the hopper 58 to lubricate the hopper so there is reduction in frictional damage to the lettuce, and to assist in maximizing the reduction of microbial propagation. The belt 36 of the elevator conveyor 48 is perforated to permit any excess disinfectant solution to drip through the belt to the ground.

TO transport the field cutter 10, the catwalks 16 are raised and the lateral conveyors 28 are raised and folded forward, thus reducing the width of the harvester platform 14. An Inverted "U"-shaped header frame 70 supports the lateral conveyor structures. The header frame 70 has two pairs of pillars attached to the frame of the harvester, one pair, positioned on either side of the longitudinal centerline of the field cutter 10, and preferably sufficiently Inboard the rear corners of the platform to permit stowage of the folded conveyors on the platform. The pillars on each side are connected to each other at the top by a cross-member, and to the opposing pillars by another cross member. This provides a rigid, simple structure on which to support the lateral conveyors 28. A hollow sleeve is disposed around each pillar of each pillar pair, A cross beam is attached to connect each sleeve of the pair to provide a slidable H-bearlng on each pillar pair. A vertically oriented hydraulic cylinder 38 is connected beneath and to the crossbeam of each H-bearing to provide hydraulic upward and downward movement of the H-bearing. The framework for each lateral conveyor 28 is pivotally connected via an arm to the rear-most sleeve of its H-bearing so that when the hydraulic cylinder 38 raises or lowers, the entire lateral conveyor 28 is also raised or lowered. Once raised and clear of the field cutter deck 14, the lateral conveyors 28 on both sides may be pivotally folded forward at the juncture of the arm and H-bearing to provide a compact configuration to facilitate either transport or storage.

As seen in Figs. 1, 2, 5 and 6, the cutter assembly 18 is enclosed in a cutter housing 72. Heads of iceberg lettuce 46 are fed into hopper 54 from the transfer conveyors 30 (Figs. 1 and 2) and then into a first, upper gang 74a of counter-rotating cutter blades 76. These are mounted as shown on a horizontal axle 78 which is powered by a hydraulic motor 80. These blades 76 are generally very thin and quite large, being typically of the order of 16-20" in diameter. The lettuce heads are gravity fed through the chamber onto the blade sets, which rotate at around 300-500 rpm. Angled guide fingers (not shown) optionally assist in guiding the lettuce in toward the intersecting nip of the counter- rotating blade gangs 74a and/or 74b. Each gang typically comprises two interleaved counter rotating sets of four to six thin, disc shaped blades (total of 8-12), each approximately .020" thick, 15-20" diameter, spaced 3" apart, which matches the preferred cut size for a prepackaged salad cut. The lower gang 76b is two sets of 4-6 interlaced blades (total 8-12 blades), in the view of Fig. 6 the Interlaced nature of blades 76 can be seen in the lower gang 74b. The upper gang 74 is similarly interlaced, although this cannot be seen well in the view of Fig. 6, since the upper gang 74 is rotated 90° horizontally as compared to the lower gang 74b. The blade spacing defines the cut size, which can be any preselected dimension.

After the lettuce 46a has been cut one way into 1 Vi- strips, it then falls by gravity into the nip of the lower gang 74b of counter-rotating blades 76 which are mounted as shown in Fig. 5 on spaced horizontal axles 78. The lettuce 46a is then discharged out of cutting chamber 40 via chute 42 onto the elevator conveyor 48. Note the relative positions of the paired nozzles 82 In the view of Fig. 6 in relation to the blades 76. Nozzles 82U are in the preferred position for the upper gang, 82L for the lower and 820 are optional. The solution is projected from the nozzles 82 in a stream onto the rapidly rotating blades 76 such that a finely divided "rain" or "fog" is created which covers the interior of the cutting assembly 18. stainless steel or plastic spacers 81 between the blades 76 assist in directing the lettuce into the cutting nip of the blades. Fig. 6A shows a first preferred position 82, a first alternate position 82a, and a second alternate position 82b for the nozzles 82 in relation to fixed blade 68, cross cut knife reel 84 and circular knives 76 of the Urschel-type cutting assembly 18a. The amount of solution injected into this cutter is 60 gph for a throughput of 7000-7500 Ibs/hr of lettuce, in the alternate, preferred, cutting assembly 18 (Fig. 6⁾, by way of example, loo gph are currently used for a throughput of 15,000 Ibs/hr. Throughputs on the order of 25,000 pph are expected to be achievable through optimization of cutter operation and scaling. While the examples herein show cut lettuce product packing in totes which normally carry approximately 47 pounds of cut product, larger containers may be used. The totes are very suitable for use with the Urschel cutter of Figs. 3, and 6A. However, for the double gang rotary cutter 18 shown in Figs. 1, 2, 5 and 6 herein, the throughput is increased to on the order of 12,000 pph, and accordingly, larger bins may be employed. These bins may be sized to carry anywhere from 300 to 700 pounds, and more typically in the range from about to 400 to 500 pounds.

The spray methods of this Invention may be adapted to a wide variety of cutters, and accordingly the placement of nozzles and cutter types shown in the figures is by way of example and not by way of limitation of the scope of the invention, in a first, preferred example, a Backus multi-gang multi- blade rotary cutter 18 is employed with at least one fluid delivery head, preferably 2-8, located in the cutter chamber 40. Typically, the fluid delivery nozzles are directed across the center of the chamber for maximal coverage of the blades and side walls. Where the lettuce heads enter from one or both sides of the cutter chamber with a horizontal velocity component, the blades may be oriented with their common rotating axis orthogonal to the horizontal component of head travel, making the plane of each blade generally parallel to the head travel. This directs the head into the nip. However, the blade plane can be orthogonal or diagonal to the direction of travel of the head coming off the conveyor belt(s). The nozzles may be mounted directly above the center of the gang, or may be mounted to the sides (as seen in Fig. 6) with a stream, fan or conical "spray delivery pattern, appropriately directed for most efficient coverage, e.g. at the point of blade contact with the heads. Likewise, spray(s) or streams of antibacterial fluid may be directed from the side(s), downwardly, or upwardly at the lower blade gang and/or to the cut lettuce as it exits the bottom of the cutter.

The concentrated hypochlorite is introduced into dilution water, either on board the harvester, or the final solution can be premixed. The solution is carried in tank 64 and pumped via lines shown to the nozzles 62, 82. it is important that the effluent (run-off) from the lettuce contain some residual free chlorine as a check that concentration and flow rates are adequate for the disinfection of a particular field's lettuce under the given environmental conditions.

As a second example shown in top view in Fig. 6A, where a Model H urschel cutter is used, a pair of fluid delivery nozzles 82 are employed directed toward the cross cut 84 and rotary blades 76 just above the stationary knife 65. The impeller drum of the Urschel Model H rotates at approximately 180 rpm, the cross cut knives rotate at approximately 872 rpm and the circular blades at 1200 rpm. The nozzle can be external as 8ia-2 with the stream entering through port 83. Preferably the nozzle is placed to seal the port as with nozzle 82a-i . The streams can be aimed at different areas of the cutter or they may intersect. The rapidly rotating cutters break up the stream into finely divided particles and distribute them thoroughly throughout the cutting chamber and the discharge chute to effectively "wet" the lettuce pieces as they are produced and rinse off the latex., other spray heads can be used, e.g., suspended above the cutter feed hopper, or directed into its impeller drum. The spray nozzles can be selectively turned on or off as conditions and/or bacterial counts dictate. The location of a fluid delivery nozzle to deliver antimicrobial treatment fluid Into the cutter chamber is deemed critical in order to accomplish microbial control through reducing bacterial propagation by the cutter, the principal mechanism of microbial spread. Of course the cutter mechanism should be made of chlorine resistant steel, such as stainless steel or the like for heavy duty use.

Where the cut product transfer belt (elevator) speed is too slow, cut product can bunch up on the flights, and the belt spray may be less effective due to shielding the main mass of the cut product by its top layer, increasing belt speed rate can assist in resolving this problem. This is also another good reason for good spray coverage in the cutter where the cut pieces are swirling around in a 3- dimensional cluster. A spray head can provide good coverage therein by the relative movement in 3 -dimensions of the cut pieces with respect to the head. The key for effective fluid delivery (streams or sprays) is more in substantially uniform distribution or coverage, as distinct from total amount (gallonage) of fluid. This is best accomplished in the cutter, although the principle can be accomplished by application of spray anywhere from cutting to packing. Thus, typically on the order of about 1.3 oz. (36 ml) of hypochlorite solution per lb. of cut product can be used. The cut product appearance ranges from damp to slightly wet, but It is not required to flood the surface of the lettuce, in contrast, in-plant operations typically require 1.25 gallons of chlorinated water/lb product. It is preferred to maintain the chlorine content above the level required to leave residual free chlorine, but below about 700 ppm because the latter can produce burning, discoloration or blistering of the lettuce. At 200-300 ppm there is no offensive chlorine odor or taste to the cut product, either fresh or after being packed in closed plastic bags and transported to a regional or local plant for further processing.

Without wishing to be bound by theory and based on observation, we believe that the core, not the leaves, functions both as the predominant source of latex and as a pump. Latex oozes from cut cores for a substantial period of time. Accordingly we prefer that the head lettuce be cored in the field immediately before being field cut. we do not observe substantial quantities of latex oozing from the treated cut lettuce pieces, which may be due to a contributory suppression of latex by the hypochlorite. Further, the aqueous component of the disinfecting spray does hydrate the lettuce, retarding wilting, overall the cut product of the invention exhibits excellent organoleptic qualities.

PROCESS EXAMPLES These examples establish that: a) the greatest site for microbial contamination is In the cutter assembly; b) microbial contamination is spread by the cutting process, and more specifically by the cutter spreading bacteria throughout the cut lettuce pieces in the absence of some control agent, such as hypochlorite; and O application of pH-adjusted hypochlorite solution in critical areas or zones In the cutter in the range of from about 200 to about 500 ppm (for a Urschei-type cutter) Is effective in control of microbial contamination, expressed as Total Aerobic Plate Count, via one or more of the mechanisms of: physical or chemical effect on latex coagulation (e.g. accelerating or altering the coagulation), and reducing, delaying, or suppressing (including kill) the inoculation, development, growth or spread of microbial contamination.

ι-_CQmBacative Field Tests in this example, field cutting both with and without disinfectant application are compared head to head. Swab tests on various process equipment surfaces, Including cutter equipment and conveyors, identified that the major source of contamination was in the cutter internals. This was established by standard swab tests for Total Aerobic Plate Count at different times after commencing field cutting in which no disinfectant was used. in this example, two identical prototype field cutting machines were employed on the same field on the same date at the same time so that environmental conditions were Identical. This was a first cutting of iceberg lettuce from the selected test field. Machine B was run with approximately 500 ppm of hypochlorlte-provided free chlorine in the spray water tank. Machine A employed spray water to equalize the hydration factor but no chlorine was used in the spray water. Both machines employed urschel Model H cutters. The antimicrobial solution of Machine B (with chlorine in the cutter chambers) was directed at the cutters in the cutter chamber (40 In Fig. 6A) by two nozzles angled in from each side to deliver streams at a total rate of 84 gph. Plain water sprays on Machine A (no chlorine in the cutter chamber) were directed to the cut product take away (delivery) elevators at a total flow of 21 gph, but none were used in the cutter chamber.

To establish a baseline, head lettuce samples were collected first thing in the morning. These heads were vacuum cooled, cored, trimmed and then cut in a local plant (without any rinse) on the same type urschel Model H cutter as used in the field cut machines. A total plate count was taken from both the intact head sample and the in-plant cut sample and compared. in addition, cut lettuce samples dOOg eachiwere collected from both field cut prototype machines

A and B at start up, after two hours of production, and after four hours of production. All cut lettuce and head lettuce samples were sent to a certified laboratory for Total Aerobic Plate count and coliform analysis.

The results are shown in Figs. 7 and 8. in addition, the input disinfectant solution was analyzed between the two and four hour samplings, and determined to contain 377 ppm free chlorine, while the run off beneath the cutter contained 182 ppm free chlorine. This indicates that the chlorine demand was on the order of 195 ppm (rounded to 200). Between those sampling times, the antimicrobial solution tank was replenished with the buffered water and hypochlorite solution to provide 573 ppm free chlorine in the spray delivered to the cutter.

Discussion

Fig. 7 dramatically shows a number of important relationships. First, the approximately 18,000 count for field heads compared to 4,000 for the in-plant cuttings indicates that the wrapper leaves, being exposed to environmental dust and dirt, are a major originating source of microbial contamination. This is reduced by about 75-80% by removal of the cap and wrapper leaves, coring, trimming and cutting in the plant. considering the direct comparison of Machine A (no treatment) to Machine B (chlorine treatment) we see that the application of the disinfectant solution to the cutter internals reduces the total plate count by 99 + % or more. Note the rise in count between two and four hours of operation of untreated Machine A. This indicates that the amount of antimicrobial treatment solution required can change during processing, depending, inter alia, on the environmental conditions, Including the amount of wind blown dust or rain spread dirt and the temperature which rises as the day progresses. The solution can be monitored to accommodate for these variations and conditions. Note that even though the total count Jumped almost three times between the two hour sample and the four hour sample for the control (Machine A with no chlorine), the increase in free available chlorine, (from 377 to 573) in Machine B, knocked the total plate count down by over 99%.

Fig. 8 shows very similar and equally striking results for Conform counts. After cooling treatment, the natural coliform count is essentially the same, at least for this test, as between the field sample heads and the heads that were cored, trimmed and cut in the plant, in all instances the high coliform count was very substantially reduced by the application of the disinfectant solution of this invention.

The Total Aerobic Plate count analysis was performed in accord with the standard test procedures set forth in the FDA's Bacteriological Analytical Manual, 8^th Ed 1995, pub by AOAC international, caithersburg MD, particularly "Ch.3, Aerobic Plate count", and "Ch.4 Escherichia coil and the coliform Bacteria", which manual is hereby incorporated by reference. Total APC includes all aerobic bacteria including coliform. The samples for the total APC and residual chlorine were 100 gram samples taken from the bags of as-cut product. The results also show increase in flow rate, increase in chlorination (concentration) and targeted application of the chlorinated spray on the internals of the cutter effectively reduced and controlled the Total APC and the coliform count compared to the machine without chlorine. The heads that were sent to the plant where the wrapper and outer leaves were removed, and the head cored, trimmed and cut, had lower plate count numbers than the raw field product heads. This indicates that a prime original source of the microbes is on the wrapper leaves of the lettuce heads.

The high Coliform count upon start up of Machine A (without chlorine) is thought to be due to contamination of the equipment from dust as the machine is transported to and driven in the field and the concentration in the cutter. Accordingly, an important optional step of this Invention is to begin chlorination treatment into the cutter for from 5 to 10 minutes prior to feeding any lettuce heads into the cutter in order to rinse down the internals. It should be noted that the "spray head" or nozzle can be adjusted to emit anywhere from a fine spray to a stream, we have found that a stream projected by the nozzle into a high rpm cutter effectively forms an "atmosphere" of fine droplets of disinfectant solution within the machine. in this test, in Machine B (with chlorine) the two Jets of treatment solution were angled in from either side of the cutter mechanism in its chamber at the top of the drum and directed at the stationary knife, the cross cut reel, and the gang of circular knives. The 84 gallon per hour treatment solution feed rate is approximately 675 gallons per 8 hour shift. The throughput of each machine was approximately 7500 Ibs/hr of head lettuce. The chlorine concentration in the disinfectant spray water range in this test from a low of about 200 ppm to a high of approximately 600 ppm with a preferred range being 300-500 ppm in Machine B.

The flow rate of the chlorinated treatment fluid can be increased to compensate for a low chlorine content ⁽concentration⁾. Accordingly, the process includes maintaining a sufficient chlorine concentration and flow rate to provide free chlorine in the run off water at a particular product throughput rate. As noted above, as the day progresses, the chlorine content in the spray water may need to be increased to compensate for environmental conditions. Typically early in the morning there is low wind and it is cool. As the day heats up and dust builds up, the chlorine content may need to be adjusted upwardly.

The spray nozzles employed were a Tee-Jet type 8004 for the entry side of the cutter and Tee-Jet type 107 for the back side of the cutter (the left and right sides in Fig. 5A , respectively). Both chlorinated water streams were delivered at 20 psi with the entry (left) Tee-Jet 8004 at 21 gph per hour with the back (right) Tee-Jet 1007 at 63 gph per hour.

il--_-Eai-ameteLD£tem-iijn---tirm_Examples

These examples, a series of tests were run to determine the acceptable operating levels of chlorinated fluid flow rates for disinfectant streams directed at the internals of the cutter to achieve a suitable level of reduction in aerobic plate count on cut lettuce exiting the field cut machine (Machine B. of Example t above). Accordingly, different chlorine concentrations and solution flow rates were tested, samples of the cut lettuce were collected from the field cut machine and analyzed for total APC for the various chlorine levels and water flow rates. Additionally, harvested raw product heads were also sampled. All samples were sent to an independent laboratory on the same day as being collected and the logarithmic APC was determined by it in accord with FDA procedures of the B.A.M. (see above). Product flow rate through the machine was at the normal 7000 to 7500 #/hr machine capacity. The test results are shown on the accompanying Figures 9 and 10, and then presented in a triaxial nomograph in Figure 11 and in a three axis graph as Figure 12. in Fig. 9, note that the plate count increases for very low levels of chlorine, above about 50 ppm.

Again, this appears to be due to a dust and dirt accumulation in the machine prior to a use of disinfectant solution introduced into the cutter internals. Note also that a rainstorm swept through the field during the test. Thus the samples after 261 ppm of free chlorine were skewed due to the rainstorm. The rainwater collecting on the lettuce heads diluted the disinfectant solution and reduced the effective chlorine concentration, it was observed that the run-off beneath the cutter, normally about 50% was Increased to about 90% during the storm, Indicating substantial dilution. The rain also increased the amount of contamination on the lettuce heads due to splattering the heads with mud from the field. This Increased the chlorine demand, so the plate count for the cutting during the rainstorm went up even though the chlorine content was increased from 260 to 371. This is another example of environmental conditions that can be compensated-for by control of free chlorine concentration or increasing treatment solution delivery rate. Thus, if, during harvesting a rain squall passes across the field, the operators can increase the available chlorine by either increasing the chlorine concentration or increasing the throughput in terms of gallons per minute, it is clear that the 50 ppm chlorine is insufficient to control the concentrating effect of microbial contamination in the cutter mechanism.

Figure 10 shows the contamination reduction by increasing free chlorine concentration and by increase of flow rate. The upper curve is for 41 gallons per hour application rate while the lower curve represents 85 gallons per hour. The APCS consistently decline with increasing amounts of either chlorine concentration and solution flow rate, indeed, with adequate flow rate, the samples at 81 parts per million free chlorine had lower APCS than the raw product.

Figure 11 is a nomograph mapping the region of acceptable microbial contamination reduction, acceptable being defined as an 80% or greater reduction in the log APC The left side axis Is the solution flow rate in gallons per hour while the right side axis is the percentage reduction in a Total Aerobic Plate Count. The various lines connecting the axes are examples of the solution sets. The natural logarithm of free chlorine was used in the nomograph (the horizontal base line) since the natural log base of 2.7 more closely approximates the cubic proportions of the chlorine level. The minimum 80% reduction in APC is achieved at a chlorine level of natural log 5.3( 200 ppm) at 42 gallons per hour of solution flow into the cutter internals. 99% reduction is achieved at a chlorine level of natural log 6.3 (545 ppm) at the solution flow rate of 85 gallons per hour into the cutter, A median point of 90% reduction of total APC occurs at a chlorine level of natural log 5.8 ( 330 ppm) at 53 gallons per hour, subsequent field experience with rotary blade double gang cutters indicates that for such equipment the 80% kill (total APC reduction) can be achieved with from about 80-200 ppm free chlorine.

Accordingly, depending on equipment and environmental conditions, an operational target range of from 50-500 ppm chlorine (preferably 80-250 ppm) and flow rate of 50-120 (preferably 70-90) gph into the cutter with 6000-10,000 Ibs/hr output, on average should provide 80-95% reduction in APC. Fig. 12 shows in three dimensional surface type graph form the effect of the treatment solution free chlorine and flow rate on the percent aerobic plate count reduction in field cut lettuce where a spray or stream of water is directed to the cutter internals. The free chlorine is on the x axis, and ranges from 60 to 545 parts ppm, while the cutter stream solution flow rate in gallons per hour is shown on the z axis and ranges from approximately 20 to 85 gallons per hour. The resultant percent APC reduction is shown on the vertical Y axis. Please note five gradiations of shading with the topmost level of 80% plus being the acceptable level.

It should be understood that these test data were developed using an Urschel type cutter. The domains, especially in the nomograph of Fig. 11 and surface graph Fig. 12, may be somewhat different in configuration or endpoints, but the general configurations will be the same and it is within the skill of the art to determine precise contours or areas for a given cutter concentration, flow rate and nozzle type by following the principles set forth herein.

lil-He-lcl-£uLLettu--i--siie.-f-L- e in this Example ill (See Fig 1), the field diced/disinfected lettuce was collected and packed in large (400-500 lb) bins containing double plastic bag liners. The bag liners were made of polyethylene with an oxygen transmission rate (OTR) of between 300-400 cc/ 100 sq inches /24 hrs. After filling the bin liners with cut lettuce from the field dicing and disinfecting operation as described above (double gang rotary disc cutters), the liners (bags) were folded over the lettuce. The letuce was cooled to 40° F or below in a vacuum tunnel within 3 hours of harvesting/dicing. After cooling, the bag liners were individually sealed. The bulk bags of cut lettuce were stored at 36° - 40° F for 10 days.

After 10 days, the lettuce was analyzed for head space gas and evaluated for visual and organoleptic properties. The oxygen level ranged between .5-2 percent and the carbon dioxide level ranged from between 6-12 percent in the bulk bags of diced/disinfected lettuce. The lettuce maintained its high visual quality and was free from any pink or brown discoloration, rotting and/or off-flavor. The field cut lettuce was then repackaged In the following steps: 1). First it was washed in chilled

20-30 PPM chlorine water; 2). Mixed with carrots and red cabbage to form a salad mix; 3). Dewatered and dried in a centrifuge; and 4⁾. packed in 1-2 lb bags made from a laminate film with an oxygen transmission rate of 180 cc 100 sq. inches /24 hrs. The bags of salad mix were stored at 40° - 45° F. The salad mix was evaluated for organoleptic qualities after 16 days of shelf life. The salad mix was highly acceptable as it was free from any visual defects and off-flavor.

The bulk bag liner material and retail bags can be a straight polyethylene, or a coextruded or laminate multi-polymeric film structure. The oxygen Transmission Rate may range from about 200 - 600 cc/100 sq. inch/ 24 hr. The maximum elapsed time between harvesting/dicing and vacuum cooling may be 1-5 hours, preferably 1-3 hours. The cooling is preferably vacuum cooling, but other conventional cooling methods may be employed. We find best results with vacuum cooling.

It is another aspect of this invention to densify the as-cut lettuce. This process is shown in Fig. 13. In the simplest form, an empty tote (with its protective inner liner) is placed beneath the product hopper outlet and the tote is filled. Then the tote is slid aside and the second empty tote is put in Its place before filling. Meantime, the cut lettuce in the first full tote Is manually compressed by applying a tamping device, for example a second empty tote having a clean protective plastic bag over its exterior, telescopingly down on top of the cut lettuce in the first tote. The lettuce is compressed by about 2/3rds, that is, to approximately l/3rd the full height of the tote. Then the compressed tote is placed back beneath the hopper, refilled, and again compressed, this time to approximately 60 to

70% of the full height. The twice compressed tote is then refilled, the plastic bag closed and the tote stacked on the forward end of the harvester platform until transferred to a local processing plant.

By this repetitive procedures of compression steps, the weight of the tote can be increased from approximately 40 to 50 pounds up to approximately 60 to 70 pounds. The ratio of weights of the compressed tote to the uncompressed tote is in the range from about 1.2 to 2, and more preferably in the range 1.25 to 1.7. Greater compression tends to bruise and damage the lettuce which should be avoided. The iterative steps are set forth in the schematic flow-sheet of Fig. 13. While we prefer to do the compression in stages, an alternative process is to do it in a single step wherein a riser member, e.g., a collar, for example, of plastic or cardboard, is placed on the upper lip of the tote and this Is entirely filled. This permits the totes to be "overfilled". Then, that entire amount may be compressed in a single stroke, the bag closed, and the tote stacked.

A wide variety of densifying means may be employed, including a powered mechanical reciprocating platen, vibration or a combination of both. The compression factors in the preferred range of 1.2-2X assume an undensified tote weighing a nominal 45 pounds, and the compression factor remains substantially the same for smaller totes or larger bins.

The resulting densified tote is then transported to the processing plant for the conventional processing of cut lettuce. The same humidification and modified atmosphere within the plastic bag applies to both the densified and undensified totes. For a given cutter throughput, it will take somewhat longer for each densified tote to be filled, and accordingly, for each load to be completed. The result is that there are fewer transfers, but this means that there is a longer period of time for the packed densified tote to remain in the field before it is transferred to the plant for cooling and processing. While it would seem that the added time in the field is a disadvantage, the additional mass in the tote compensates for the additional time by virtue of the fact that there is a greater thermal mass in each tote. Thus, the net result is that the densified totes as delivered to the plant have very little temperature differences compared to undensified totes.

It Is important that the platen or tote that is used to compress the as cut lettuce remain clean and not become a source of bacterial contamination. Accordingly, a fresh bag can be placed over the compressing tote, or the compressing tote bottom or the side of the platen contacting the cut lettuce can be sprayed with the antimicrobial solution described herein to disinfect and remove latex produced by the produce and released during the cutting.

Another important aspect of the invention is the removal of latex. Accordingly, field harvesting (e.g. by hand-severing the lettuce head from the root), coring In the field, and use of water or disinfectant solution to rinse (or other means of removal) of latex from the head of cored lettuce is a significant method for microbial control, and is part of this invention. Also included, is halving and quartering the head. This significantly reduces pink discoloration. Likewise, in-plant coring and/or dicing/slicing can be accomplished by disinfectant spray of the coring and/or dicing mechanism, and/or spray on the base of the lettuce head being cored, and/or the head being diced.

INDUSTRIAL APPLICABILITY it is clear from the above description and examples that the process and apparatus of the invention is directly applicable to field harvesting of head lettuce and other produce as it results in longer shelf life and productivity increases on the order of over 30%. it should be understood that various modifications within the scope of this invention can be made by one of ordinary skill in the art without departing from the spirit thereof. For example, in place of, or in addition to hypochlorite as a disinfectant, the following may be used: clean water; halogenated inorganic compounds (Iodine, bromine, fluorine); antioxidants; ozone; reducing agents; anti-browning agents; PH modifiers and buffers; electrolyzed solutes; UV; ultrasound and the like, we therefore wish our invention to be defined by the scope of the appended claims as broadly as the prior art will permit, and in view of the specification if need be.

Claims

1. A method for field cutting of produce comprising the steps of: a⁾ conveying of freshly harvested produce to a cutting apparatus to form a plurality of bite sized product pieces; b⁾ providing an antimicrobial solution in sufficient quantity and having a sufficient concentration of disinfecting agent to control microbial propagation in said cutting apparatus; and c⁾ applying said antimicrobial solution to cutting elements of said cutting apparatus and onto product pieces during cutting of said produce.

2. A field cutting process as in claim 1, wherein said antimicrobial agent Is a hypochlorite solution.

3. A field cutting process a in claim 1, wherein said antimicrobial solution is provided in an amount and concentration sufficient to provide free chlorine in the rate of from above about 60 to about 700 parts per million.

4. A field cutting process as in claim 2, wherein said antimicrobial solution is provided in an amount sufficient to provide excess free chlorine in residual solution draining off said cut produce pieces.

5. A field cutting process as in claim 4, wherein said excess chlorine is in the order of above about 50 parts per million.

6. A field cutting process as in claim 1 wherein said antimicrobial solution is provided in an amount and for a duration sufficient to reduce total Aerobic Plate count above about 80%, as compared to untreated cutting apparatus.

7. A field cutting process as in claim 2, wherein said hypochlorite solution has a free chlorine concentration and is provided at a flow rate sufficient to provide effective contact of chlorine with cutter apparatus surfaces to reduce total APC by above about 80%.

8. Method of field harvesting produce including head lettuce comprising the steps in operative sequence of: a) severing the produce in the field from its root, and coring and trimming it as needed; b) conveying in said field said harvested produce heads to a cutter having a cutting mechanism in a chamber; c) dicing said produce heads into ready to eat salad-cut size pieces; d) simultaneously while dicing, introducing a disinfectant solution into said slicer chamber in an amount and at a concentration sufficient to reduce total APC by about 80%; e) discharging said cut produce pieces Into a single or multiple use collection bag or other container supported in a one way or reusable transport container; f) closing said collection bag to maintain sufficient moisture and humidity conditions to retard deterioration during transport to further processing or market.

9. A field cutting and disinfecting process as in claim wherein said produce is head lettuce.

10. A field cutting and disinfecting process as in claim 9 wherein said disinfectant is chlorine.

11. A field cutting and disinfecting process as in claim 10 wherein said chlorine is provided hypochlorite, and is present in an amount sufficient to result in residual free chlorine after application on said cut lettuce on the order of in excess of about 50 ppm.

12. A field cutting and disinfecting process as in claim 8 which includes the additional step of spraying a disinfectant solution on said cut produce pieces during conveyance to a packing station.

13. A field cutting and disinfecting process as in claim 8 wherein said cutter is an impact type cutter.

14. A field cutting and disinfecting process as in claim 13 wherein said disinfectant solution is delivered through nozzles disposed above and on at least one side of said cutter chamber.

15. A field cutting and disinfecting process as in claim 18 wherein the disinfectant solution present in the cutter chamber is in a finely divided condition.

16. A field cutting and disinfecting process as in claim 8 wherein said disinfectant solution is provided at least in part in a stream directed at a rotating cutting mechanism in said chamber which breaks up the stream into fine droplets which are redirected to and wet surfaces of the produce passing through the cutting mechanism and surfaces of said cutting mechanism.

17. A field cutting and disinfecting process as in claim 8 wherein said cutter is a double-gang, rotary disc type cutting mechanism.

18. A field cutting and disinfecting process as in claim 17 wherein said disinfectant solution is introduced into contact with said cutter blades In the range of from about 60 to 350 ppm in an amount ranging from about 50 to about 120 gph.

19. A field cutting and disinfecting process as in claim 8 wherein said field cutting is followed by in-plant processing which includes at least one washing and one dewateπng step.

20. A field cutting and disinfecting process as in claim 19 which includes the step of drying said washed and dewatered diced lettuce prior to bagging.

21. A process as in claim 20 which includes at least one step of cooling said field cut produce.

22. A process as in claim 21 wherein said cooling includes at least one step of vacuum cooling.

23. A process as in claim 22 wherein said drying step includes employing heated air.

24. A process in claim 23 wherein one of said vacuum cooling steps occurs after said drying step.

25. A process as in claim 22 wherein said cut produce is vacuum cooled before said in-plant processing.

26 A field cutting and disinfecting process as in claim 8 which includes the step of densifying said cut produce at a packing station in the field by compaction prior to closure of said transport bag.

27. A field cutting and disinfecting process as in claim 25 wherein said compaction densif les said field cut produce to within the range of from about 1.25 to about 2 times the density of uncompacted field cut produce.

28. A process as in claim 8 which includes at least one step of cooling said field cut produce.

29. A process as in claim 28 wherein said cooling Includes at least one step of vacuum cooling.

30. An apparatus for field cutting and disinfecting produce, particularly head lettuce, comprising in operative combination: a) a harvester having a frame mounted on wheels; b) a cutter mounted to said frame; c) conveyor means mounted to said frame disposed to deliver harvested head produce to said cutter, d) a reservoir mounted on said frame for retaining a quantity of disinfectant solution of size sufficient for several hours of field operation; e> aqueous solution delivery lines for delivery of aqueous disinfectant solution from said reservoir to said cutter; f) fluid delivery nozzle means disposed to direct aqueous disinfectant solution into said cutter mechanism in a manner which results in coverage of the cutter surfaces and surfaces of cut produce during operation; and g) means for collection of cut produce from the discharge end of said cutter.

31. Apparatus as in claim 30 which includes a discharge conveyor extending from the discharge end of said cutter to a delivery station.

32. Apparatus as in claim 31 which includes a platform on said harvester for stacking empty containers before processing and containers of cut produce.

33. Apparatus as in claim 30 which includes means for packing said produce in controlled atmosphere containers.

34. in a method of harvesting head lettuce which includes the steps of separating the lettuce head from its root and placing it in containers for shipment, the improvement which comprise the steps of: a) coring the lettuce heads in the field; b) field cutting the cored head lettuce to produce cut lettuce pieces: c) placing said cut lettuce pieces in transport containers; and d) densifying said cut lettuce pieces before transport.

35. An improved lettuce harvesting process as in claim 34 wherein said densificatlon step includes compressing said lettuce in said transport container in at least one stage.

36. An improved lettuce harvesting process as in claim 35 wherein said compression is carried out in multiple steps and each compression step compresses the uncompressed lettuce portion no more than about 2/3rds of its original volume.

37. An improved lettuce harvesting process as in claim 35 where said densification step includes providing a riser collar extending above the top lip of said transport container; filling said container with cut lettuce pieces to above the top lip of said transport container so that the collar retains excess cut lettuce pieces, and compressing said lettuce to the height of said transport container top lip

38. An improved lettuce harvesting process as in claim 34 wherein said transport container is a tote lined with a plastic bag which is closed after said densification step.

39. An improved lettuce harvesting process as in claim 35 wherein said densification compression employs a second nestable tote, the bottom of which is used as a compression platen.

40. An improved lettuce harvesting process as in claim 34 wherein said densification step includes vibrating said cut lettuce into or in said inset transport container to assist in compaction.

41. in a cutter assembly comprising a housing defining a cutting chamber having a cutting mechanism mounted therein, the improvement which comprises: a) at least one fluid delivery nozzle positioned in association with said chamber such that an antimicrobial solution is sprayable onto the cutting mechanism in said chamber.

42. A field crop harvesting system, comprising: a) a cutting assembly; b) a platform having mounted therefrom a conveyor system extending laterally such that a crop placed on said conveyor is moved into said cutting assembly; and c) at least one fluid delivery nozzle positioned such that the internal mechanism of the cutter and crop being cut therein is sprayed with an antimicrobial solution.

43. A method of harvesting head lettuce which comprises the steps of a) separating the lettuce head from its root; b) coring and trimming the head; c) cutting the cored head to produce cut lettuce pieces while removing the latex; d) packing said cut lettuce pieces.

44. A method of microbial control during produce harvesting or processing comprising the steps of:

a) coring the produce; and b) treating the cored produce to remove latex from the cored area.

45. A method as in claim 44 wherein said treatment step includes use of disinfectant solution.

46. A method as in claim 44 which includes the step of field harvesting and said steps of coring and treating occur in the field.

47. A method as in claim 8 wherein said collection bag Is a consumer package.