IL45193A - Process of air evacuation of foods under ultra-low pressure - Google Patents

Description

Process of air evacuation of foods under ultra-low pressure Fehmerling Associates BACKGROUND OF THE INVENTION This invention relates genex-ally to a process for treating foods such as marine creatures, fruits and vegetab to improve their appearance, texture, storage characteristi and the time necessary for processing these foods for prese vation. More particularly, the present invention relates t a process for treating various foods with an extremely high vacuum to remove substantially all gases including deleteri oxygen and substituting for the evacuated gases , a liquid s as to distend the cell walls of the food prior to conventio processing and preserving the foods.

All natural foods have a limited storage life capac due in part to entrapped air in the tissue voids and within the cells of the food and also due to the presence of vario enzymes naturally occurring in the foods as well as microorganisms inherently present or picked up during any proces procedure. The present invention is primarily directed to problems arising from the presence of air which, because it includes oxygen, permits the growth of various organisms producing deleterious results. It is well known, for insta that various proteins, carbohydrates, naturally occurring pigments, vitamins and delicate flavor constituents are oft partially oxidation. Obviously, this undesired oxidative process not only adversely affects the appearance of the product but th The presence of oxygen is particularly in foods because of the detrimental effects upon preservation and storage characteristics, but also because of the deterioration in the natural color of fruits. The red color in all fruits, for instance, deterioriates rapidly due to the reaction with oxygen. There is produced as a result of this action, brown to black shades of color. The catalyst for this reaction is sunlight, and it is for this reason that some fruits -particularly cranberries - cannot be packed in other than an opaque container which would shield them from the catalytic rays of light. Cranberries and other similar fruits are, therefore, precluded from being packed in glass containers and lose the consumer appeal that a see-through package commands.

Other color changes are also traceable to the destructive presence of oxygen. Green vegetables, such as broccoli, for instance, lose the desirable green color due to the degradation of the chlorophyll during thermal processing The discoloration of the tissue of other fruits, such as the browning of apples, by reason of the presence of oxygen has been noted.

Oxygen not only supports deleterious chemical reactio relating to color, but also promotes the growth of microorganisms naturally present in the foods. The microorganisms when permitted to thrive in the presence of oxygen, degrade the cell structure of the tissues in time to produce a rubber like, soft or weak texture which is uncharacterisic of the food and is generally found to be unacceptable by the consumer.

There are also problems in the processing of a number of foods which are to be impregnated with sugar, salt or other material. For example, a sugar concentration that may vary between 30% up to 50% or 65% may be desired.

A number of variations have been commercially used for the impregnation of cranberries, but principally the cranberries are immersed in a sugar solution after being pricked, and the solution in time is expected to impregnate and then equilibrate with the interior of the cranberry. This is a slow process, but even more importantly, it is ineffective in producing a quality stable product.

For the cherry and cranberry and for other fruits and vegetables, this technique fails to fill the cells of the fruit with liquid. The fruit, then, as finally processed, j is oftentimes Shrunken in size due to the subsequent collapse of the cell walls from heating or freezing. This shrinkage usually appears on the surface as wrinkles or undulations which detract from the appearance of the fruit. Also, there is a loss upon storage of the natural fluid of the fruit from these ruptured cells. In the case of the cranberry or other small seed bearing fruit, the seeds are lost from the fruit and are mixed in the syrup in the final container. The seeds, added to the portions of the broken cells present, produce an undesirable non-clear syrup.

These fruits, therefore, not only require an unecono mically long period of time for* processing, but frequently result in a product which is partially shrunken in size, has a tendency to weep, loses portion of its cell structure and contents, possesses poor storage characteristics due to the incomplete removal of oxygen, may change color from its natural state due to oxidation, and promotes microorganism growth.

In general, these products often have poor taste, texture, shape and color.

PRIOR AKT It is recognized that prior art procedures attempt to cure certain of these defects through an evacuation of gases present in the various foods and substitution with desirable liquid. The vacuum in any of these methods is usually a maximum of 28 inches of mercury as in eckel, U.S. Patent No. 2,865,758. In older methods, equipment was not adequate to obtain much higher vacuums while subsequent continuous procedures are not capable of achieving an extremely high vacuum and remain continuous. These prior art procedures, however, were in part effective in removing some of the deleterious oxygen from the food but never achieved any meaningful improvement in either the storage characteristics or cell integrity. Even a small amount of remaining oxygen is found to be sufficient to support activity of a group of enzymes naturally present in the foods and capable of producing off-flavors and off-colors in the products during storage.

Higher vacuums applied did not result in a comraercial usable process. Such products subjected to vacuums greater than 28 inches Hg either ruptured the cellular tissue or still left residual gases within the fruit. The prior art never recognized the importance of using only pressures near perfect vacuum combined with exercising great care in a particular manner and for a minimum time in the drawing and release of such vacuum to prevent rupturing the cell tissue. Very low pressures were known to the art as typified by Fisher, U.S. Patent No. 2,801,925 and Guadagni, U.S. Patent No. 2,702,248 to exhaust gases from fruits and Weckel suggests slow evacuatio and release of vacuum at a maximum of 28 inches of vacuum but no stable unruptured product ever has been made commercial based upon these or any other prior art process. In fact, no process is known that removes and replaces substantially all the gases entrapped within a fruit with an appropriate liquid without permitting any undesirable breakdown in cell integrity.

OBJECT OF THE INVENTION It is accordingly the principal object of the present invention to provide a process for for the removal of air and other gases from the tissues and flesh of fruits, by completely immersing the product in a liquid and applying and releasing in a unique manner an extremely low pressure to exhaust substantially all of the gases from the food product without rupturing the cellular structure of the fruit.

DESCRIPTION OF THE INVENTION It has been discovered that the residual gases remaining after exposure to vacuum as high as may have been used in a prior art, permit a residual quantity of oxygen and other gases to remain in the tissue which is larger than might be expected. Eve the highest prior vacuums if applied to the fruit would not completely remove the residual gases unless applied for a sufficiently long time and then unless the vacuum was drawn and released in a minimum required time collapse of the cells would result.

The significance in the ultra reduction in the pressure applied to the food to bo processed can be vividly brought out by an experiment conducted with a pound of mush-rooms. The mushrooms were cleaned and washed in the usual fashion and immersed in a quantity of water so that the top of the mushrooms were below the level of the water and a vacuum of 28 inches was applied and maintained for 2 hours. During the first 30 minutes of the vacuum, approximately 1 small bubble of air per 10 minutes was withdrawn after the firs 30 minutes of the vacuum treatment. After 1 hour and 20 minute no further bubbles were forthcoming, indicating that all of the gas that could be removed at 28 inches of vacuum was, in fact, removed. Thereafter, the vacuum was increased to 29.993 inches of mercury and immediately a multitude of bubbles too numerous to count passed through the tube from the vacuum chamber and continued bubbling at a rate of approximately 1 bubble per 5 minutes between 1 hour and 1 hour and 50 minutes. During the next and final 10 minutes for a total of 2 hours, no further bubbles were noted. A more detailed illustration is set forth in Example II.

To illustrate the maximum pressure at which the fruit could be completely evacuated, the following procedure was performed upon a closed flask containing nicked cranberries submerged in syrup.

Vacuum was applied and pressure slowly reduced to dwell points of 635mm llg , 510mm, 400mm, 135mm, 60mm, 13mm.

Temperature was maintained at 20.5°C. during the experiment. Three minutes were allowed at each pressure with 2 minutes allowed for reduction in essure to the next lower pressure. Essentially, bubbling ceased by the end of each of, the three minute dwell times. Gases were collected in flasks. Upon completion of the gas withdrawal, the flasks receiving the gases were placed in a 20°C. chamber and with the bottom stop cock submerged in a tank of water and opened while submerged the flasks were allowed to reach equilibrium of temperature (20°C). At the end of 2 hours the bottom stopcock on each flask was closed. Flasks were reweighed and loss in weight was determined. By calculation to standard temperature and pressure, the actual volume of gases withdrawn at each pressure reduction was determined (calculated) : Pressure, mm. Hg. Vacuum, Inches Hg . % Gases Withdrawn 635 5 11 510 10 23 400 15 37 135 25 72 60 28 81 13 29.5 100 Determination similar to this in nature, indicated that pressures on the fruits to be processed should not exceed 13mm of mercury for total evacuation. In proportion to the decrease in pressure and the length of time of the application of the high vacuum, the quantity. of air evacuated is completely unexpected. It is not understood why such additional lowering of the pressure produces the disproportionate evacuation of gases except for several theories such as the need to exceed the threshhold retention force between the residual gas and the food tissues by means of the ultra-low applied pressure.

It has been discovered, therefore, that the pressure of 13mm is the maximum pressure which may be applied to the beyond the barrier holding the ror.idual gases and to sub tantia evacuate all the gases including the deleterious oxygen. More preferably, the evacuation of the vessel should be down to pressure of 2.0mm. Lower pressures could be used, but since th impregnating solution evaporates quickly, the partial pressure of the liquid sets a practical limit upon the lowest pressure that may be achieved at the temperature range of 20 F - 70°F. The preferable pressure is below 5mm Hg at a temperature range of 30°F - 35°F.

The time for continuing the evacuation procedure of the present invention is quite important. The evacuation of the gases should continue until there are no further gases removed as seen, for instance, from the bubbling through the submersing liquid. Specifically, it has been found that at least 1 hour dwell time is essential for application of the vacuum at pressures between 2 and 13mm Hg. Significant advantages are achieved when the pressure is applied for a period exceeding 1-1/4 hours and most ideally the maximum advantage of the present invention not obtainable for shorter times is achieved when the vacuum is applied for at least 1-3/4 hours. For the impregnation of fruits with high solid content solution, longer times are required as mentioned in connection with cherries. Cranberries, for instance, generally require a 1-3/4 hour dwell time. Generally a 2 hour dwell time is advisable. The total dwell time beyond 2 hours is limited only by economics. The liquid impregnating medium is usually an aqueous solution of sugar or salt, the concentration of whic is not critical and may vary from 0% to the maximum concentrati possible at the working temperature. Any other soluble flavor The manner of applying and releasing the vacuum applied to the immersed fruit is another important aspect of the present invention. It has been found that in its broadest critical aspects, the reduction in pressure should be continua from atmospheric down to pressure of 200-300mm of mercury, preferably 250mm Hg, at a maximum rate of decrease of 125mm of mercury per minute preferably 50-lOOmm per minute. The tota time of these steps of lowering the pressure must be at least 28 minutes. From this pressure down to the working pressure between 2 and 13mm mercury, the rate of lowering the pressure must not exceed a rate of 12mm per minute. After the dwell time of at least one hour at the lowest pressure,1 the pressure may be increased up to 55-65mm of mercury, preferably 60mm, at a rate that does not exceed 12mm per minute and from 55-65mm to atmospheric at a maximum rate of 35mm. per minute. The total time for these steps of raising the pressure must be at least 28 minutes. - These pressure reductions and release times are particularly critical above and below the low pressure attained during the dwell time and require the slow rates of 12mm per minute maximum. The preferable total minimum time for each ste is from 760inm to 250mm in 5 minutes at a preferable rate of 100mm per minute/ from 250 to the dwell pressure in about 25 minutes at a preferable rate of 10mm per minute a 1 hour dwell, 5 minutes to release vacuum to 60mm at a preferable rate of 10mm per minute and 25 minutes from 60mm - atmospheric at a preferable rate of 30mm per minute. The total time for the evacuation and impregnation is at least 1 hour and 56 minutes and preferably greater than 2 hours. Greater times may be used Increasing the timer, for accomplishing each step by lowering the maximum rate of pressure change to the' above preferable rates significantly improves the characteristics of the resulting products out of proportion to the magnitude o the changes.

It has been found that during the lowering of pressu and the build up, that there are critical pressure areas in which the cellular structure is particularly sensitive to pressure changes. To avoid rupturing of the cells and also to insure complete removal of the gases, the rate of build up and release of the pressure are important.

It is also found that not greater than 50% by volume (STP) of the gases should be removed in the initial step of lowering of the pressure to 200-300mm Hg.

It has been theorized that the. specific manner of redticing the pressure and building up pressure after the proper dwell time -is important principally due to the fact that air and other gases expand a significantly greater volume than liquids under the imposition of a vacuum. By slowly reducing the pressure to and particularly below 200-300mm Hg over an extended period of time of at least 28 minutes at maximum rates of 125mm per minute and 12mm per minute respecti ly for each period, the gases naturally present in each fruit cell initially cause a distension of the cell wall thus increasing the volume of each cell. The cell being semi-permeable, the gases gradually migrate through the cell wall and are quantitativel displaced with the liquid medium into which the fruits have been submerged. The gases escape as bubbles in ho the medium and arc drawn off by the vacuum.

Reduction or increases in pressure exceeding the statedd limit.? results in the cell walls rupturing before the gases are able to migrate through the wall and be replaced by liquid.

To avoid rupture Of the cells after the present vacuum treatment all the gases must have been evacuated and the cells filled with liquid. The evacuated fruit then is at osmotic equilibrium with its surrounding liquid medium. These equilibrated fruits so evacuated and impregnated with liquid medium are then capable of withstanding adverse conventional thermal processing that may be thereafter employed to preserve the fruits.

When properly treated in accordance with the present invention, no gases remain in the fruit to expand into the far greater volume than would be expected for liquid expansion, thus the cells of the fruit being devoid of gases are not subject to the various degrees of collapse of tissue otherwise occurring in heat processing. Such collapse of tissue results in the softening of the entire fruit and a loss of cell integri Without the presence of gases during the heat processing step, the cell wall will inherently thicken as a result of the reacti among the natural fruit acids, pectin and sugar which may be present to various degrees. This thickening forms a gel which coats the cell walls to further aid in minimizing the loss of cellular fluid during storage. By permitting the thickening of the cell walls in the tissue due principally to the gelling of the natural fluids and solids in the fruit, subsequent heating such as in the packaging or even the baking of pies or casseroles substantially eliminates the normal destructive effect of heating due to the ability of heat to transfer rapidl throu h the medium and into the e uilibrated fruit.

Upon freezing, the fruit treated in accordance with the present invention, the fruit freezes more rapidly and more uniformly. Ice crystals which otherwise would be rather large and capable of puncturing the cells to create a loss of cellular material, are maintained significantly smaller, thus minimizing the number of cells that would be ruptured either by freezing or defrosting. The capability of the fruit so processed to withstand the rigors of freezing and defrosting and yet continue to retain its normal shape and texture without loss of weight, is one of the significant I advantages of the present invention.

The process of the present invention may be understoo from a general example using preferred but not essential items of equipment. It is only significant to utilize apparatus which is capable of producing, maintaining and withstanding the ultra-low pressure and which has means for retaining the products treated below the surface of the liquid placed in the vessel. Additionally, suitable inlets and outlets for the liquid must be located on the vessel.

The following procedure will generally describe the manner of achieving the benefits of this invention: The fruits are conventionally prepared by washing, peeling, cutting, or dicing as required. The product is then placed in a vessel made of non-reactive material such as stainless steel, steel covered with plastic material, or any structurally sound material that can be sanitized readily.

The vessel is preferably equipped with an inlet port located at or near the top. Immediately below the port, the entire surface of the vessel is pa titioned off by a perforated plate of the vessel. After the vessel is filled to capacity jwith ^ -product, below the false top, the port is securely fastened to exclude air and the vessel is filled from a pipe at the top wit the desired solution. The level of the solution is adjusted-to completely cover the product and to maintain a level approxi mately 1/2 inch above the perforated top throughout the process This assures complete coverage of the product. with solution. The solution inlet pipe is now closed. A mechanical pump or venturi steam evacuator operating to produce a vacuum is activated to draw a vacuum on the vessel from a pipe located at the top of the vessel. When steam venturi is used, it operates only to reduce pressure to about 20 inches of vacuum. It is recommended that a high performance pump take over and complete the evacuation of the remaining air and gases. In order to avoid the necessity of outsized pumps, it is recommended that a condenser be positioned before the inlet side of the pump to condense the vapors that may be withdrawn from the vessel. The condenser may be liquid cooled and generally should cool the vapors to a temperature of 10 to 15°C preferably, or -20 to +30 Such a condenser will substantially reduce the volume of the vapors that must be handled by the vacuum pump.

The vacuum reacts by destroying the threshhold barrier and displacing gases in the tissues of the product until essentially all of the gas is withdrawn. The more complete evacuati obtained, i.e., the lower the pressure within the range of 2-13 Hg during the dwell time, the less time required for complete displacement of the gases with liquid surrounding the product. Whatever the specific absolute pressure within the specified range, it is necessary to lower the pressure from atmospheric to 200- 300mm at a maximum rate of per minute and f om 200-300mm llcj to 2~13mm Hg at a maximum of 12mm per minute, provided that these steps of lowering the pressure consume at least 28 minutes before the one hour minimum dwell time at the lowest pressure and thereafter to increase the pressure up to 55-G5mm at a rate not exceeding 12mm per minute and from 55-65m to atmospheric at a maximum rate of 35mm per minute provided th these steps of lowering the pressure consume at least 28 minute Evacuation of gas and replacement with liquid is complete in a minimum of 1 hour and 56 minutes which may be broken down into pressure reduction and pressure build up periods of at least approximately 28 to 30 minutes duration and a dwell time of at least 1 hour. Any of these times may be up to 20-fold greater than the minimum "with corresponding decreases in the rates of drawing and releasing the vacuum.

Upon retaining atmospheric conditions , a port in the bottom of the vessel is opened and the product and liquid drain out of the vessel. Product and liquid then pass over a drainin screen or vibrating separator from which the product may or may not go into water or a steam blancher . Blanching inactivates the enzymes present and shrinks the product which squeezes out excess liquid without allowing air or other gases to enter the tissue.

Another method employed is to partially fill tubs with the produce, cover with a perforated top and fill the tub with the desired solution to a point above the level of the product. The tubs -are then wheeled into a chamber capable of withstanding a pressure of 2mm llg. Thereafter, the product may be preserved by canning, freezing or even dehydration in the usual manner.

EXAMPLE I - CRANBERRIES Five pounds nicked cranberries were placed in a tub and covered with 7 pounds of 62.5° Brix syrup. The tub was placed in a vacuum chamber and pressure reduced uniformly to 250mm Hg absolute in 5 minutes and then to 10-12mm Hg at a rate of 10mm per minute, the pressure of 10-12mm Hg was maintained for 1-3/4 hours. Pressure returned to 60mm Hg (absolute) at a rate of increase of 10mm Hg per minute in 5 minutes and thereafter gradually increasing the pressure for 23 minutes to atmospheric at a rate of 30mm per minute. Berries and syrup were placed in stainless steel pot and heated to 160 °F. Berries were filled into clear glass jars, jars then filled with hot 160°F. syrup, and closed. Jars were then inverted to sterilize lid and air cooled.

It should be stressed that cranberries treated by the present vacuum process do not require heating above 160 °F. for preservation, whereas other processes require at least 180°F. to 200°F. fill temperature plus 20 minutes processing of the closed containers in water at 180 °F to 200 °F. The berries of the present invention require no thermal processing after placing in jars at 160°F.

This is brought about by the absence of oxygen in the tissues of the berries which would support the growth of microorganisms of the type which could grow in the highly acid conditions which is attained in the berries and syrup pack.

The following advantages are apparent in the cranberries produced according to the present process as compared to those of the prior art: 1. The present cranberries require no further process after being placed in the container hot, as opposed to all of the other processes known in the industry. 2. The present cranberries require no additives to aid in preservation, color retention or to artificially induce firmness to the products. 3. In the present process the cranberries retain their original crisp and crunchy texture and do not become soft or leathery as they do when processed by the other methods 4. Color of cranberries by the present process remain normal during process and storage as opposed to cranberries produced by other methods. 5. In the present process the weight of the product is stabilized at the packaged weight. Initial weight gain by the present process is greater than that achieved by the other processes. 6. By the present process, the syrup remains clear and free of seeds and particles of cranberry, as opposed to cranberries produced by other methods. 7. When containers of cranberries are opened at atmospheric pressure, those processed by the present invention retain their original round plump, symmetrical shape while all of the fruits processed by the other methods tend to wrinkle and become dimpled. 8. The present process requires less equipment and labor input than any other known vacuum process.

The present process recognizes that cranberries are composed of roughly 88% liquid and other components and a small amount (about 1%) of gases. The fact that the air and gases expand at about 18 times the rate of water or liquid in the presence of heat and, partially, under vacuum, is what makes presence of these elements, even in very small amounts, so important. And it is essential that the gases and air are removed very carefully in a narrowly controlled range of low pressure, time of vacuum application, time of dwell and time of It is equally important that as the air and gases are removed from the cells, that they are immediately and completely filled with liquids, under con of displacement of air and gases with liquids into the cells mu be simultaneous and under carefully controlled conditions. By proper application and release of vacuum, the cells are thus sealed and future loss of liquids and/or collapse of the cells are prevented. Also, air and gases are the enemy of color in cranberries and other fruits and vegetables, thus removal of essentially all of the air and gases as described herein is essential to retention of good, normal color in the products during storage.

The following are other specific examples of the wide range of fruits that may be processed in accordance with the present process.

Example II - Mushrooms Exactly 100 pounds of mushrooms, commercially referre to as "cut" mushrooms, that is, whole mushrooms with only roots cut from each unit were taken from 24 plastic crates of nine pounds each crate. * Mushrooms with obvious defects such as brok units, units with roots attached and those with widely open veils were removed. The mixed bin of mushrooms varied in size from a diameter of 5/8 inch to 1-3/4 inches. The lot was equal divided into two lots of exactly 50 pounds each.

Vacuum Treated Lot The fifty pounds of mushrooms were washed on scre by sprays of water and placed in a plastic bin, they were leveled in the bin and covered with a rigid plas i sheet containing 3/8 inch perforations which fitted tightly against the sides of the plastic bin. The co was weighted with plastic pails partially filled with water. The mushrooms were covered with a 2% brine mushrooms and cover. The tub of mushrooms wasi placed in a vacuum chamber connected through a1 refrigerated condenser to a two stage vacuum pump. Tempei-ature of brine and mushrooms was 56°F. The cha ber was closed and vacuum pump started.

Pressure was reduced to 250mm Hg at a rate of 100mm Ug per minute and then down to.10mm Hg at a rat of 10mm Hg per minute for a total time of about 29 minutes. Vacuum treatment at a pressure of 10mm merc was continued for 2 hours . At the end of 2 hours , the vacuum pump was shut off and a valve, between the pump and the chamber was closed. A valve to let air into the vacuum chamber was opened and the pressure i the chamber was returned to atmospheric pressure by increasing the pressure to 60mm Hg in 10 minutes at a rate of approximately 5mm per minute and then to atmospheric at a rate of approximately 35mm per minut for a total time of pressure increase of about 30 minutes. The tub of mushrooms was removed from the vacuum chamber , brine was drained from the mushrooms which were then reweighed. The weight of the vacuum treated mushrooms was 73.75 pounds. The vacuum treat mushrooms were blanched in a thermo-screw steam blancher for 5.5 minutes. Weight of the blanched mushrooms was 43.75 pounds. Blanched mushrooms were plunged into cold water and cooled to below 70°F.

Cooled mushrooms were filled into cans at 8 ounces ±. ounce, a salt tablet was added and boiling water was added to cans to overflow. Cans were conveyed auto" " in retort crates and thermally processed for 27 minutes at 250°F. Cans were then cooled in running water, air dried and cased and cartons marked "treated The number of 'cans filled was 87. Calculated on original weight of 50 pounds of raw mushrooms, this is a yield of 87%, or conversely, a loss of 13% from rav; to canned weight. Further results of testing of canned product is found in Table #i .

Control - (Conventional Commerical Procedure) Fifty pounds of mushrooms (1/2 of the 100 pound lo were soaked, after washing, for thx-ee hours in 2% brin solution, while the vacuum treatment was being applied to the treated mushrooms as described above. The control mushrooms were drained and weighed after soaki and the weight was 55.5 pounds. The control mushrooms were blanched 5.5 minutes, plunged into cold water, drained and reweighed, the weight was found to be 32.0 pounds. Blanched control mushrooms were filled into cans at 8 ounces ±.1 ounce, a salt tablet added to each can and filled to overflowing with boiling v/at Cans were automatically conveyed to the "paddle packer sealed and retorted (thermally processed) for 27 minutes at 250°F. Cans were cooled in running water, air dried and cased, the cases were marked "control". The number of control cans filled was 64. Calculated on original weight of 50 pounds of raw mushrooms, this is a yield of y64%, or conversely, a loss of 36% from raw to canned weight. Further results of testing of canned product is found in Table Mushrooms processed conventionally must be stored for at least several months to allow bleaching of the mushroom tissue by stannous salts dissolved from tin of the container. Such storage is not required of vacuum treated mushrooms. It is of great importance that no darkening occurs in vacuum treated mushrooms during processing because essentially all of the oxyg has been displaced by liquid in the mushroom cells.

Vacuum treated mushrooms, therefore, can be shipped Firm texture of thermally processed vacuum treated mushrooms occurs immediately after cooling In the case of conventionally processed mushrooms, several weeks must elapse to allow mushrooms to "set II the texture, that is, to lose their "spongy" mouth fe 2. Vacuum treatment results in a significant saving the processor by a lowering of losses in weight attendant to processing mushrooms. Average weight loss throughout the mushroom processing industry approximates 40%. That is, for each 100 pounds of mushrooms with roots removed purchased by the processor, he actually processes 60 pounds of mushrooms.

I By vacuum treating mushrooms by the present process, losses are reduced to less than 20%.

The following summary of data relating to the treatme of mushrooms further illustrates the significance of not only the low pressure, but the times and rates of application of the pressure changes : 1. Lower "pressure to less than 13mm Hg in 10 minutes, retain this pressure for 2 hours, return to atmospheric pressur in 30 minutes with the mushrooms constantly submerged, produced an average weight yield of 71%. 2. Lower pressure to less than 13mm Hg in 30 minutes, retain this pressure for 2 hours, return to atmospheric pressur in 10 minutes with the mushrooms constantly submerged, produced an average weight yield of 74%. 3. Lower pressure to less than 50mm Hg in 30 minutes, retain this pressure for 2 hours, return to atmospheric pressur in 30 minutes with the mushrooms constantly submerged, produced an average weight yield of 66%. 4. Lower pressu e to less than 13mm Jig in 30 minu d ,~ retain this pressure for 2 hours, flood mushrooms with brine while maintaining this pressure and return to atmospheric pressu in 30 minutes produced an average weight yield of 64%. 5. Lower pressure to 250mm Hg at a rate of 125mm per minute, then to 13mm Hg at a rate of 10mm Hg per minute in a total time of 28 to 30 minutes, retain this pressure of 13mm Hg for 2 hours, raise to 60mm Hg at a rate of 10mm per minute and then to atmospheric at a rate of 35mm Hg per minute in a total time of pressure increase of 28 to 30 minutes, the mushrooms constantly being submerged, produced an average weight yield of 84%.

It is established, therefore, that reduction in pressu to less than 13mm Hg and the increase in pressure to atmospheric must be accomplished no more rapidly than 28 minutes each to assure greatest yield and highest quality product. " It is critical to substantially remove all air and gases and replace them with liquid in the mushroom cells to obtain osmotic equilibrium between the mushrooms and the surrounding medium.

Example III - Apples Vacuum Treated Apples of Staymen variety were peeled, cored and sliced with automatic equipment in a commercial apple processing plant .

Five thousand grams of apple slices were placed in a plastic tub and covered with a rigid plastic plate containing 3/8 inch perforations. ^ he plate was weighted with water.

Apple slices in the tub were covered to 3 inches over the plastic plate with syrup composed as follows: water - 1600 part This syrup lrovidcd a quantity of sulfur dioxide based upon syrup and apples of 7 5 parts per million. Temperatur of syrup and apples was 60 . 5 ° F . Tub of apples was placed in a vacuum chamber which was sealed. A two stage vacuum pump connected through a refrigerated condenser to a vacuum chamber was started and vacuum gradually drawn and released as in Exampl II except that the pressure was 13mm Hg. , The tub of apples was removed from the chamber, apples were drained free of syrup and weighed. The treated apples weighed 6 , 045 grams, a gain of 20 . 9 % . Treated apples, with no syrup added, were divided into 3 equal portions of 2 , 000 grams each and placed in friction lidded cans. Two of the cans were stored in a commercial blast freezer within four hours.

One can was held at room temperature for 20 days. Forty-five grams of apples were sealed in a jar for immediate analysis.

Control The 6 , 045 grams of the same lot of apples described above were treated in normal commercial manner by soaking for 4 minutes in the same solution as the vacuum treated apples except the standard commercial volume of sodium bisulfite was used to produce 1, 600 parts per million sulfur dioxide. Soaked apples were drained, 2 , 000 grams were placed in each of 3 fricti lidded cans. Two cans were stored in a commercial blast freezer after 4 hours at room temperature. One can was held at room temperature for 20 days. Forty-five grams of apples were sealed in a jar for immediate analysis.

Chemical Analysis Samples of Apple Slices.

Core of Apple Slices Treatment Brix Control 10.7° Vacuum Treated 14.6° Whole Slices Control 12.8° Vacuum Treated 14.6° These results confirm penetration of sulfur di the syrup uniformly through the apple slices d Table # 3 Comparison of quality, texture and drained wei frozen apple samples.

Penetr Treatment Drained Weight Reading Control 1730 g. (86.5%) 8.1 lbs.( Vacuum Treated 1920 g. (96.0%) 10.9 lbs. ( 1. he significant difference in drained weights s'li that freezing ruptured many cells of the untreated control appl slices causing loss of liquids. This reduces the numbers of pies that can be produced from a can. 2. Texture of treated fruit was crisp even after freezing and defrosting whereas the control fruit was flabby and rubbery, not characteristic for Staymen apples. 3. Very serious "Browning" occurred in control apple due to enzyme activity not inhibited by sulfur dioxide as a result of poor penetration into the center of the slices. For high quality of pies, units with serious browning would have to be removed by sorting.

) Example iv ' - Shrimp Ten pounds of Pandalus Borealis shrimp were used in this Example. Five pounds of shrimp identified as "vacuum treated" were headed and peeled by hand and submerged in an aqueous solution composed of 0.5% citric acid and 2.5% sodium chloride in a stainless steel bucket at 52°F. The shrimp were kept submerged by a weighted stainless steel wire screen. The bucket of shrimp was placed in a retort connected to a vacuum pump and the vacuum treatment of Example II applied except that in the dwell time the vacuum was applied for only 1 hour, after which the shrimp were removed from the bucket, drained and blanched for 1.5 minutes in an aqueous 2% sodium chloride solution. The shrimp were immediately placed into cans at 8 ounces per can, brined with a 1.5% sodium chloride solution containing 0.5% citric acid at 195°F. The cans were closed by an automatic closing machine and thermally processed in a retort for 45 minutes at 240°F. The cans were then cooled to a temperature of 110°F. in the retort by running water.

Following the present commercial procedure, five pounds of the shrimp identified as "control" and prepared identically as described above, were submerged in an aqueous solution of 0.5% citric acid and 2.5% sodium chlorj.de at a temperature of 52°F. for 45 minutes. The shr.imp were then drained, blanched and placed into cans as described and' processed in the identical manner as the "vacuum treated" shrimp.

Twenty-four hours after processing, 6 cans of each pack were examined for quality in accordance with Industry Standards. Headspace analysis was made in accordance with National Canners Association procedure.

Vacuum Treated Results of Analysis Samples Control Samples Drained wt. , range 6.8 to 7.1 oz. 6.5 to 6.6 oz . Drained wt. , average 6.95 oz . 6.52 oz .

Color Brilliant red Slightly dull red Curl All units Some units rightly curled slightly curled Flavor Typical Weak, typical Oxygen content headspace, range 0.25 to 0.33% 3.65 to 4.55% Oxygen content headspace, average .0.27% 3.99% Color, flavor, and general appearance of the shrimp were significantly improved by "vacuum treatment" to remove oxygen from the tissue prior to processing.

Other marine creatures in which color, flavor, aroma, and weight retention have been improved by vacuum treatment and various combinations of brines are crab meat, clams oysters, scallops and mussels. There is a particularly dramatic improvement in appearance and drained weight of clams insofar as color is concerned by the present process.

These examples are to be considered illustrative of the present invention and in no manner are limiting of the scope of the invention. For instance, instead of a two stop increase bo used provided it is within the herein designated max mum χ-atc of pressure change and minimum time.

Claims (18)

I CLAIM: j Λ ί

1. The process of enhancing the appearance, textur and storage characteristics of foods selected from the group con sisting of fruits, vegetables, marine creatures and mushrooms by removing substantially all gases from the tissues and cells of said foods and substituting therefore an aqueous solution int the said tissues, the process comprising: submersing said foods in said solution containe in enclosed vessel, subjecting said submersed foods to a reduction in pressure down to 200-300mm mercury at a rate of pressure decrease not greater than 125mm of mercury per minute, further decreasing the pressure from 200-300mm mercury to a pressure not greater than 13mm of mercury (absolute) at a rate of pressure decrease not greater than 12mm mercury per minute, both said pressure decrease steps consuming at least a total of 28 minutes, continuing to subject said submersed foods to an absolute pressure of not greater than 13m of mercury for a dwell time period of at least 1 hour to substantially remove all gases from said tissue and cells, increasing the pressure thereafter to fill with said solution the voids formed in said tissues and cells by the evacuation of the gases, said pressure increase being performed by incre ing the pressure up to 55- 65mm of mercury at a rate of pressure increase not greater than 12mm of mercury per minute, further increasing the pressure from 60mm of mercury up to atmospheric pressure at a rate of pressure increase not greater than 35mm of mercury per minute, both said pressure increase steps consuming at least a total of 28 minutes, whereby said food are substantially filled with said solution and there after removing said foods from said vessel.

2. The process of claim 1 wherein said dwell time is at least one hour and three-quarters.

3. Process of claim 2 wherein said dwell time is at least 2 hours.

4. The process of claim 1 wherein said pressure during the dwell time is within the range of 2-13mm of mercury.

5. The process of claim 1 wherein the dwell pressu is within the range of 2-13mm of mercury and the dwell time is at least one hour and three-quarters in the fruit.

6. The process of claim 5 wherein the total time exceeds approximately 2 hours.

7. The process of claim 1 wherein the pressure decrease down to 200-300mm of mercury is at a pressure decrease rate of between 50 and 100mm of mercury per minute.

8. The process of claim 1 wherein not greater than 50% by volume (STP) of gases are removed within the first ten minutes .

9. The process of claim 1 wherein said foods include marine crea^tures selected from clams, shrimp, crab, scallops, mussels, oysters, lobsters; fruits selected from cherries, apples, pears, apricots, blueberries, strawberries, peaches and the like; vegetables selected from peas, corn, lima beans, strin beans , cauliflower, onions, asparagus, brusscl sprouts, -carrots potatoes, broccoli and tho liko. 1

10. The process of claim 1 wherein the pressure is first decreased at a maximum rate, Of 100mm per minute, then decreased to not. greater than ¾3mm Hg at a rate not greater tha 10mm Hg per minute. '

11. The process of claim 1 wherein the pressure is raised to 60mm Hg at a maximum rate of 12mm Hg per minute and from 60mm Hg to atmospheric at a maximum rate of 30mm Hg per- minute.

12. The process of claim 1 wherein the total \ time for the pressure increase and the total time for the pressure decrease steps ace each 30 minutes.

13. The process of claim 1 wherein the pressure is first decreased at a maximum rate of 100mm per minute, then decreased to not greater than 13mm Hg at a rate not greater than 10mm Hg per minute, and wherein the pressure is raised to 60mm Hg at a maximum rate of 12mm Hg per minute and from 60mm Hg to atmospheric at a maximum rate of 3Oram Hg per minute, and ■ ' wherein the total time for the pressure increase and the total time for the pressure decrease steps are each 30 minutes. /

14. The process of claim 13 wherein the total time for the process is at least 2 hours.

15. The process of. claim 1 wherein said foods are ■ i . cranberr

16. The I process of claim 1 wherein d foods are

17. The products of the process of claim 15.

18. The products of the process of claim 16. , For the Applicants Dr. Yitzhak Hess /