CA1043160A - Dehydro-frozen vegetable process and product - Google Patents
Dehydro-frozen vegetable process and productInfo
- Publication number
- CA1043160A CA1043160A CA211,822A CA211822A CA1043160A CA 1043160 A CA1043160 A CA 1043160A CA 211822 A CA211822 A CA 211822A CA 1043160 A CA1043160 A CA 1043160A
- Authority
- CA
- Canada
- Prior art keywords
- freezing
- celery
- process according
- frozen
- vegetables
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Storage Of Fruits Or Vegetables (AREA)
- Freezing, Cooling And Drying Of Foods (AREA)
- Preparation Of Fruits And Vegetables (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Processed prepared vegetables such as celery are pro-duced in a form which provides preferred color, texture and flavor attributes by dehydrating to remove approximately 35-55% of the water originally present and thereafter individually quick-freez-ing the produce employing a freezing plateau of up to 10 minutes.
Processed prepared vegetables such as celery are pro-duced in a form which provides preferred color, texture and flavor attributes by dehydrating to remove approximately 35-55% of the water originally present and thereafter individually quick-freez-ing the produce employing a freezing plateau of up to 10 minutes.
Description
1~4~0 This invention relates ~o new forms of processed vegetables, and typically celery and peppers, which heretofore exhibited a loss of crispness when frozen and more particularly it concerns the process whereby such produce will now retain an appreciable degree of desired crisp texture after freezing.
Certain produce such as celery manifest an undesired loss of texture as a result of freezing, and/or canning.
To explain, the typical structure of fresh celery ; will consist of a thin, continuous boundary of epidermal cells which protect the inner tissues from physical damage and water loss. Underneath the epidermis will be found a layer of paren-chymatype cells which may be involved in a number of functions.
Directly under the epidermis to a depth whereat light may pene-trate, the parenchyma cells are pigmented and involved in photosynthesis; this tissue will be referred to as the hypo-dermis. As one progresses away from the hypodermis and peri-meter of the stalk, these underlying cells are larger in size and function as storage tissue for the stalk. The bulk of the stalk tissue is the cortex made up of thin walled parenchyma cells.
Upon conventional freezing of celery the tissue systems are disrupted greatly. The epidermis will be generally torn loose from the tissue beneath it with only a few random pieces attached to the underlying collenchyma bundles and a random attachment to the hypodermis. The hypodermis will be dislocated as will the collenchyma bundles which as viewed will appear to be torn out of place and surrounded by large voids where thin parenchyma tissues were torn away from them. The parenchyma tissue which makes up the bulk of the cortex also 1~)43:~60 suffers much damage; the cell walls are torn apart and randomly located throughout. Vascular bundles also are torn apart into separate tissues. Overall the fresh-frozen celery will be con-siderably damaged and almost all of the tissue systems will be disrupted to a large extent resulting in a loss of crispness.
This damage is largely due to the physical stresses of ice crystal formation. Size and type of ice crystal is partially a function of freezing rate, but in all commercial equipment, damage is significant with low solids turgid products such as celery.
Prior art workers have suggested the practice of de-hydrofreezing fruits and vegetables including such produce as apples and peas which have been optimized in processing by cus-tomary food technology routes such as variety selection, slice sizing, control of blanching conditions and the like. The primary incentive for dehydro-freezing is the economical advantage of shipping in the order of 50% less weight compared to fresh-frozen or canned produce. Weight reduction results in substantial savings in refrigerated transportation, storage charges and handling labor.
According to the invention there is provided a pro-cess of produeing frozen preserved vegetables which eomprises redueing the moisture eontent of the vegetable to aehieve a weight reduetion of 35-55%, and then freezing the vegetable under freezing eonditions having a freezing plateau of less than 10 minutes.
The present invention is founded upon the diseovery that dehydro-frozen eelery and like produee redueed in moisture eontent to broadly 45-65% (i.e. a weight reduetion of 35-55%) 104~i0 and preferably uniformly to 50-60% (i.e. a weight reduction of 40-50%) of its original weight relieves the strain of freezing such that there is generally less tissue damage provided also that the vegetables are frozen rapidly, which rapidity can best be expressed by the products having a brief freezing plateau or that time during the total freezing cycle when the product temperature remains essentially constant. (In this connection, such fast freezing is to be contrasted with static freezing at, say, 0F or even blast freezing at -40F whereat a relatively slow growth of water ice crystals occasions ice crystal growth sufficient to induce cell damage and loss of crispness parti-cularly upon rehydration.) Dehydro-frozen celery, reduced and frozen as describ-ed above can be easily restored or reconstituted to its orig-inal weight and solids content, exhibiting texture and flavor superior to that of conventionally frozen celery.
The improvement in dehydro-freezing stemming from this invention is not to be restricted to any particular theory. However, it is believed that with vegetables which derive their structural integrity from high osmotic pressures within the cells per se and which suffer most upon freezing because of cell rupture, such as celery and bell peppers, and carrots to a lesser degree, by employing the aforestatéd mois-ture reduction there is simply less water to freeze and with the resultant faster freezing rates, particularly in individual quick freezing, one promotes smaller crystals and less con-sequent cell damage. In addition, by increasing the concentra-tion of water soluble compounds by partial dehydration, one increases the degree of super-cooling and enhances the ., .
1~4:~60 spontaneity of crystallization of the water present. It is believed that this occasions a delay in the change of state but that once crystallization starts, it proceeds rapidly with only small crystals being formed, the presence of water soluble com-pounds in a concentrated state influencing not only crystal growth but also alteration of the type of crystal.
In this connection, it is important to recognize there is a criticality such that if one overdrys there will be irreversible cell damage simply due to dehydration and other adverse quality effects occurring during freezing which result in an inferior and inadequately reconstituted product when com-pared with conventional produce such as frozen fresh celery.
If, on the other hand, one does not partially dry enough, concentration of solubles and the effect thereof on ice crystal formation is not significant, enough to minimize substantial cell damage. It is believed that by adopting a 35-55% weight reduction, there is a sufficient increase of soluble concentra-tion in the produce's aqueous phase to supplement the benefits that stem from a rapid freezing.
Freshly harvested celery is washed, rinsed, deleafed, trimmed and sliced in a slicer set up to produce 3/8" thick transverse cuts. No chemical additives need be added to the product. The sliced celery is deposited onto a shaker screen which serves to remove undersized pieces and small broken pieces with some leaf. The uniformly spread product is fed to a water blancher wherein the product is blanched at 200F for one minute. The product discharging from the blancher is then hydro-cooled rapidly by a cooling water system which reduces overall slice temperature to below 60~F by maintaining the ~04316~ :
cooling water at a temperature of 45F.
The hydro-cooled slices are then essentially uniform-ly dehydrated in a two-zone through-circulation hot air dryer whose circulating air temperature at no time exceeds 165F.
Hot drying air entering the first stage of the dryer has a temperature not exceeding 165F and leaves the dryer at 150F
in the first zone thereof. Product entering the second zone is exposed to air not exceeding 150F and in its terminal stages of dehydration product will be exposed to no heat. Thus, the product will be uniformly dried while in a bed depth of 1-2".
The sliced celery will thus be reduced from an initial solids content of 6.25-7.25% to a final solids content of 12.5-14.5%.
The thus reduced sliced celery will then be individually quick frozen so as to emerge from a freezer at between 0F and -10F employing a freezing plateau of 2-5 minutes. Preferably a moving bed or fluidized bed freezer is employed; an immersion freezer employing liquid nitrogen or freon may also be employed providing a relatively instant freezing plateau. Generally speaking, product quality and particularly texture will improve as the freezing rate is increased, faster freezing resulting in smaller ice crystals and minimization of cell damage.
The products produced by the present invention exhibit generally better texture and flavor relative to conven-tionally frozen unreduced counterparts in the class of celery and peppers. Cell integrity is relatively well preserved. ~
Whereas the epidermis is torn away from the hypodermis of a -celery piece and takes a portion of the hypodermis with it, the hypodermis is still present and recognizable even though it has - . . . . . .
: . . . . . ..
.
' ' ,, ' .
1~)43~60 been split. Collenchyma bundles are still intact with a few voids present there-around. The parenchyma tissue in the cor-tex does appear erupted and the cells have burst open, but cell walls appear more numerous and the large voids present in a frozen control which has not been reduced are not visible. The effects on cell structure are most manifest in relation to a control when the specimens are thawed and rehydrated, a re-hydrated dehydro-frozen celery slice for instance produced in accordance with this invention will return to at least 95% of its original weight and when compared with regularly frozen celery, will have an improved texture, as is, as well as in both canned and refrozen applications.
Although the invention has been described by particular reference to celery, it is of equal application to other vegetables which are prone to undergo significant changes in their morphology due to freezing such as peppers as explain-ed above.
Certain produce such as celery manifest an undesired loss of texture as a result of freezing, and/or canning.
To explain, the typical structure of fresh celery ; will consist of a thin, continuous boundary of epidermal cells which protect the inner tissues from physical damage and water loss. Underneath the epidermis will be found a layer of paren-chymatype cells which may be involved in a number of functions.
Directly under the epidermis to a depth whereat light may pene-trate, the parenchyma cells are pigmented and involved in photosynthesis; this tissue will be referred to as the hypo-dermis. As one progresses away from the hypodermis and peri-meter of the stalk, these underlying cells are larger in size and function as storage tissue for the stalk. The bulk of the stalk tissue is the cortex made up of thin walled parenchyma cells.
Upon conventional freezing of celery the tissue systems are disrupted greatly. The epidermis will be generally torn loose from the tissue beneath it with only a few random pieces attached to the underlying collenchyma bundles and a random attachment to the hypodermis. The hypodermis will be dislocated as will the collenchyma bundles which as viewed will appear to be torn out of place and surrounded by large voids where thin parenchyma tissues were torn away from them. The parenchyma tissue which makes up the bulk of the cortex also 1~)43:~60 suffers much damage; the cell walls are torn apart and randomly located throughout. Vascular bundles also are torn apart into separate tissues. Overall the fresh-frozen celery will be con-siderably damaged and almost all of the tissue systems will be disrupted to a large extent resulting in a loss of crispness.
This damage is largely due to the physical stresses of ice crystal formation. Size and type of ice crystal is partially a function of freezing rate, but in all commercial equipment, damage is significant with low solids turgid products such as celery.
Prior art workers have suggested the practice of de-hydrofreezing fruits and vegetables including such produce as apples and peas which have been optimized in processing by cus-tomary food technology routes such as variety selection, slice sizing, control of blanching conditions and the like. The primary incentive for dehydro-freezing is the economical advantage of shipping in the order of 50% less weight compared to fresh-frozen or canned produce. Weight reduction results in substantial savings in refrigerated transportation, storage charges and handling labor.
According to the invention there is provided a pro-cess of produeing frozen preserved vegetables which eomprises redueing the moisture eontent of the vegetable to aehieve a weight reduetion of 35-55%, and then freezing the vegetable under freezing eonditions having a freezing plateau of less than 10 minutes.
The present invention is founded upon the diseovery that dehydro-frozen eelery and like produee redueed in moisture eontent to broadly 45-65% (i.e. a weight reduetion of 35-55%) 104~i0 and preferably uniformly to 50-60% (i.e. a weight reduction of 40-50%) of its original weight relieves the strain of freezing such that there is generally less tissue damage provided also that the vegetables are frozen rapidly, which rapidity can best be expressed by the products having a brief freezing plateau or that time during the total freezing cycle when the product temperature remains essentially constant. (In this connection, such fast freezing is to be contrasted with static freezing at, say, 0F or even blast freezing at -40F whereat a relatively slow growth of water ice crystals occasions ice crystal growth sufficient to induce cell damage and loss of crispness parti-cularly upon rehydration.) Dehydro-frozen celery, reduced and frozen as describ-ed above can be easily restored or reconstituted to its orig-inal weight and solids content, exhibiting texture and flavor superior to that of conventionally frozen celery.
The improvement in dehydro-freezing stemming from this invention is not to be restricted to any particular theory. However, it is believed that with vegetables which derive their structural integrity from high osmotic pressures within the cells per se and which suffer most upon freezing because of cell rupture, such as celery and bell peppers, and carrots to a lesser degree, by employing the aforestatéd mois-ture reduction there is simply less water to freeze and with the resultant faster freezing rates, particularly in individual quick freezing, one promotes smaller crystals and less con-sequent cell damage. In addition, by increasing the concentra-tion of water soluble compounds by partial dehydration, one increases the degree of super-cooling and enhances the ., .
1~4:~60 spontaneity of crystallization of the water present. It is believed that this occasions a delay in the change of state but that once crystallization starts, it proceeds rapidly with only small crystals being formed, the presence of water soluble com-pounds in a concentrated state influencing not only crystal growth but also alteration of the type of crystal.
In this connection, it is important to recognize there is a criticality such that if one overdrys there will be irreversible cell damage simply due to dehydration and other adverse quality effects occurring during freezing which result in an inferior and inadequately reconstituted product when com-pared with conventional produce such as frozen fresh celery.
If, on the other hand, one does not partially dry enough, concentration of solubles and the effect thereof on ice crystal formation is not significant, enough to minimize substantial cell damage. It is believed that by adopting a 35-55% weight reduction, there is a sufficient increase of soluble concentra-tion in the produce's aqueous phase to supplement the benefits that stem from a rapid freezing.
Freshly harvested celery is washed, rinsed, deleafed, trimmed and sliced in a slicer set up to produce 3/8" thick transverse cuts. No chemical additives need be added to the product. The sliced celery is deposited onto a shaker screen which serves to remove undersized pieces and small broken pieces with some leaf. The uniformly spread product is fed to a water blancher wherein the product is blanched at 200F for one minute. The product discharging from the blancher is then hydro-cooled rapidly by a cooling water system which reduces overall slice temperature to below 60~F by maintaining the ~04316~ :
cooling water at a temperature of 45F.
The hydro-cooled slices are then essentially uniform-ly dehydrated in a two-zone through-circulation hot air dryer whose circulating air temperature at no time exceeds 165F.
Hot drying air entering the first stage of the dryer has a temperature not exceeding 165F and leaves the dryer at 150F
in the first zone thereof. Product entering the second zone is exposed to air not exceeding 150F and in its terminal stages of dehydration product will be exposed to no heat. Thus, the product will be uniformly dried while in a bed depth of 1-2".
The sliced celery will thus be reduced from an initial solids content of 6.25-7.25% to a final solids content of 12.5-14.5%.
The thus reduced sliced celery will then be individually quick frozen so as to emerge from a freezer at between 0F and -10F employing a freezing plateau of 2-5 minutes. Preferably a moving bed or fluidized bed freezer is employed; an immersion freezer employing liquid nitrogen or freon may also be employed providing a relatively instant freezing plateau. Generally speaking, product quality and particularly texture will improve as the freezing rate is increased, faster freezing resulting in smaller ice crystals and minimization of cell damage.
The products produced by the present invention exhibit generally better texture and flavor relative to conven-tionally frozen unreduced counterparts in the class of celery and peppers. Cell integrity is relatively well preserved. ~
Whereas the epidermis is torn away from the hypodermis of a -celery piece and takes a portion of the hypodermis with it, the hypodermis is still present and recognizable even though it has - . . . . . .
: . . . . . ..
.
' ' ,, ' .
1~)43~60 been split. Collenchyma bundles are still intact with a few voids present there-around. The parenchyma tissue in the cor-tex does appear erupted and the cells have burst open, but cell walls appear more numerous and the large voids present in a frozen control which has not been reduced are not visible. The effects on cell structure are most manifest in relation to a control when the specimens are thawed and rehydrated, a re-hydrated dehydro-frozen celery slice for instance produced in accordance with this invention will return to at least 95% of its original weight and when compared with regularly frozen celery, will have an improved texture, as is, as well as in both canned and refrozen applications.
Although the invention has been described by particular reference to celery, it is of equal application to other vegetables which are prone to undergo significant changes in their morphology due to freezing such as peppers as explain-ed above.
Claims (8)
1. A process of producing frozen preserved vegetables, selected from the group consisting of celery and bell peppers, which comprises reducing the moisture content of the vegetable to achieve a weight reduction of 35-55%, and then freezing the vegetable under freezing conditions having a freezing plateau of less than 10 minutes.
2. A process according to claim 1, wherein the vegetable is blanched, hydrocooled and dried with circulating hot air not exceeding 165°F to achieve a weight reduction of 35-55%.
3. A process according to claim 2, wherein the product is dried to achieve a weight reduction of 40-50%.
4. A process according to claim 1, wherein the reduced vegetables are individually quick frozen.
5. A process according to claim 4, wherein the vegetables are celery or bell peppers.
6. A process according to claim 4, wherein the reduced vegetables emerge from the freezer at a temperature of 0°F to -10°F.
7. A process according to claim 5, wherein the freezing plateau is 2-5 minutes.
8. Dehydro-frozen celery and bell peppers reduced in moisture content to 45-65% of their fresh moisture content when produced by the process according to claims 1 and 6.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA211,822A CA1043160A (en) | 1974-10-21 | 1974-10-21 | Dehydro-frozen vegetable process and product |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA211,822A CA1043160A (en) | 1974-10-21 | 1974-10-21 | Dehydro-frozen vegetable process and product |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1043160A true CA1043160A (en) | 1978-11-28 |
Family
ID=4101402
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA211,822A Expired CA1043160A (en) | 1974-10-21 | 1974-10-21 | Dehydro-frozen vegetable process and product |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1043160A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4461781A (en) * | 1982-05-03 | 1984-07-24 | Societe D'assistance Technique Pour Produits Nestle, S.A. | Freezing of vegetables |
| ES2326510A1 (en) * | 2008-04-10 | 2009-10-13 | Blanca Rosich Ferrer | Procedure for freezing horticultural products (Machine-translation by Google Translate, not legally binding) |
| WO2009125041A1 (en) * | 2008-04-10 | 2009-10-15 | Blanca Rosich Ferrer | Method for freezing fruit and vegetable produce |
| ES2328891A1 (en) * | 2008-04-10 | 2009-11-18 | Blanca Rosich Ferrer | Method for freezing hortofruticolas products (Machine-translation by Google Translate, not legally binding) |
| US7897189B2 (en) | 2005-11-16 | 2011-03-01 | Fresh Defrost Ltd. | Apparatus and techniques for freezing and thawing of agricultural produce |
-
1974
- 1974-10-21 CA CA211,822A patent/CA1043160A/en not_active Expired
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4461781A (en) * | 1982-05-03 | 1984-07-24 | Societe D'assistance Technique Pour Produits Nestle, S.A. | Freezing of vegetables |
| US7897189B2 (en) | 2005-11-16 | 2011-03-01 | Fresh Defrost Ltd. | Apparatus and techniques for freezing and thawing of agricultural produce |
| ES2326510A1 (en) * | 2008-04-10 | 2009-10-13 | Blanca Rosich Ferrer | Procedure for freezing horticultural products (Machine-translation by Google Translate, not legally binding) |
| WO2009125041A1 (en) * | 2008-04-10 | 2009-10-15 | Blanca Rosich Ferrer | Method for freezing fruit and vegetable produce |
| ES2328891A1 (en) * | 2008-04-10 | 2009-11-18 | Blanca Rosich Ferrer | Method for freezing hortofruticolas products (Machine-translation by Google Translate, not legally binding) |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN100367862C (en) | Method for swelling and watering fruit or vegetable type food at ambient temp. | |
| US5368873A (en) | Process for preparing dehydrated vegetable products | |
| EP0564573B1 (en) | Process for preparing dehydrated aromatic plant products and the resulting products | |
| CN101129146B (en) | Method for processing dewatered fruits and vegetables | |
| JPH0284129A (en) | Dry food of fruit and vegetable | |
| US4396636A (en) | Method for producing frozen-food | |
| FI78224C (en) | Förvällningsförfarande | |
| CN102014642A (en) | Method for freezing fruit and vegetable produce | |
| US4194016A (en) | Process for preparing precooked fruits and vegetables | |
| US5723167A (en) | Compressed frozen vegetables and process of making | |
| BROWN | Texture of frozen fruits and vegetables | |
| US8007852B2 (en) | Method for production of frozen vegetables or fruits | |
| US9204658B2 (en) | Process for the production of frozen foods, particularly vegetables or fruits | |
| CA1043160A (en) | Dehydro-frozen vegetable process and product | |
| CN107518059A (en) | A kind of quick-frozen fresh vegetables processing technology | |
| US3511668A (en) | Artificially sweetened freeze dried food | |
| US5589213A (en) | Dual-stage process for manufacturing potato chips | |
| CA2000546C (en) | Vegetable products with improved stability at freezer temperatures and process for producing same | |
| AU678558B2 (en) | Process preparing stabilized, partially-dehydrated aromatic plant products and the resulting products | |
| EP0166600A2 (en) | Method for producing freeze-dried strawberry slices | |
| US4517210A (en) | Process for preparing a fruit and cereal product | |
| EP0339112B1 (en) | Blanching process | |
| US2729566A (en) | Process for preparing dehydrated potatoes | |
| JPH0355088B2 (en) | ||
| AU700243B2 (en) | Process of preparing compressed partially dehydrated vegetables |