JPH02257827A - Vegetable product having improved stability at freezing temperature and making thereof - Google Patents

Abstract

PURPOSE: To produce vegetable products which may be preserved and stored over a long period by partially dehydrating vegetable products and adding water active control materials thereto to adjust water activity to <1, then lowering the product tap. to a temp. below zero. CONSTITUTION: The vegetable products are partially dehydrated and the water active control materials, such as sodium chloride and sodium citrate, are added thereto to adjust the water activity of the vegetable products measured at 20 deg.C to <1, for example, about 0.5 to 0.9, more particularly about 0.7 to 0.85, by which the moisture content is made smaller than the moisture content of the untreated vegetable products, for example, to about 20 to 50%, more particularly 25 to 45%. In addition, both of the water activity and the moisture content are so adjusted that the vegetable products exist flexibly and as non-frozen at a typical sub-zero frozen food storage temp. The temp. of the vegetable products is then lowered down to a typical sub-zero frozen food storage temp., for example, about -20 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a novel cold-stable vegetable product and a method for producing the same.

[Prior Art and Problems] Many methods are known for preserving and storing food products for both short and long term periods. Freezing is one such method.

Frozen foods, especially plants (vegetables) and plant products, are important as commercial items in industrial, consumer, and food service markets. The quality and acceptability of frozen plants
Although generally considered satisfactory, this type of food preservation has some inherent disadvantages.

After freezing, foods such as plants must be kept at subzero (Celsius) temperatures. Frozen foods that are partially or completely thawed and then refrozen suffer a significant loss in quality. Frozen foods that are accidentally thawed or thawed for a period of time awaiting use can result in spoilage and a public health hazard.

Some products, such as peas, beans and diced carrots, can be quick-frozen individually, while other plants can be frozen into solid blocks that need to be thawed before a measured amount can be used. It freezes. Even plants that are individually flash-frozen will clump together into clumps on storage as a result of freezing of the water between the plant pieces.

The energy required to freeze water in plants is considerable, and so is the cost. Also,
Freezer storage is expensive, as is freezer shipping.

Freezer transport is always unstable as far as keeping the product frozen is concerned.

Some of the costs associated with storage and transportation are covered by “dehydration and freezing.”
This can be significantly reduced by the known method. In this method, the plants are dehydrated by up to 30% of their initial weight and then frozen. Dehydration freezing can reduce freezing, backing, storage and transportation costs by up to 60%. However, the product still freezes hard, resulting in tissue damage, and is more easily thawed due to its higher solids content than normal. This presents the thawed product with spoilage problems in much the same way as a thawed normally frozen product.

Various methods of plant dehydration are known and several are used industrially. In most of these methods,
The plants are dried to a low moisture content, usually less than 7%,
In the case of freeze-dried plants, the plants are often
It is also dried down to 2 to 3%. At this moisture content the plants are hard and very brittle. Therefore, a large amount of breakage occurs and excess waste (small plant pieces and fibers) is generated. This is especially true for leafy vegetables.

Normal air-dried plants exposed to relatively high storage temperatures for long periods of time with low moisture content undergo substantial deterioration in flavor, color and aroma.

Stable dehydrated plants with higher than normal water content are
Lewis and Lewis (Australian Patent No. 53241)
No. 4, U.S. Patent Section 4.447.460 and U.S. Pat.
683.141) by adding salt to reduce the water activity of partially dried plants. With this method, the upper limit of moisture level is 25%, but longer pot stability is generally achieved at moisture levels at the lower end of the hygrometer.

For example, onions tend to gradually discolor when stored at moisture levels above 10%. At less than 10% moisture, onion slices are brittle enough to break. Many dehydrated white plants or white tissues of other plants (e.g., internal petiole of celery, white tissue of zucchini, pale yellow leaves of cabbage or Chinese cabbage, and white cucumber tissue) are
Darkens relatively quickly during storage. Furthermore, many green and light green plants, whether in solute-added form or normally dried form, have a water activity of 0.5 or higher and a water activity of 2 at room temperature.

If stored for more than three months, the green chlorophyll pigment will deteriorate. Still other plants, especially leafy vegetables, become weak and brittle when dehydrated in any form;
Available only as flakes or powder. Such include spinach, parsley, meboki, cabbage, chives, and similar plants and herbs.

The shelf life of dehydrated vegetable products can be increased by storage at low temperatures. Lower storage temperatures reduce the chemical reactions that lead to deterioration. However, at freezer storage temperatures - in the shell, from 0°C to -25°C, normal dehydration and solute addition products become more brittle and break down.

A number of foods have been described that can be stored at freezer temperatures without freezing. These include butter (Kern et al.
U.S. Pat. No. 4.154.863), emulsion cream-type food products (Khan et al., U.S. Pat. No. 4.313,
No. 987), egg yolk (Khan et al., U.S. Pat. No. 4.244.
976), flake juice (Kern et al., U.S. Pat. No. 4,418,082), flakes (Kern et al., U.S. Pat. No. 4,350,711), oil-in-water emulsions (
No. 4,387,109) and "foamable" food products (Kern et al., US Pat. No. 4,148,852). All of these rely on very high concentrations of sugar for their non-freezing performance. This level of sugar is incompatible with fresh plant products.

The addition of solutes to control water activity in intermediate moisture has been documented (Lewis et al., U.S. Pat.
．． No. 447,460, U.S. Pat. No. 4,683.141 and U.S. Pat. No. 4.384.009). Solutes have also been added to foods to produce frozen foods with special advantages (Lam, U.S. Pat. No. 3.219.48).
No. 1, Allis et al., U.S. Pat. No. 4,478,888), but is not intended to produce non-freeze foods.

[Means for Solving the Problem] The present inventor has discovered that a highly stable and high quality vegetable product intended for storage below 0°C can be obtained in a "non-destructive" and flexible form. I found it.

The invention relates to a method for preserving a vegetable product at sub-zero temperatures, the product being treated by first partially dehydrating and adding at least one water activity controlling substance to the product. and thereby increase water activity (water
acHvHy) less than 1 (measured at 20°C), a moisture content lower than unprocessed plant products, and both water activity and moisture content that are flexible at typical sub-zero frozen food storage temperatures. Second, it includes reducing the temperature of the product to typical sub-zero frozen food storage temperatures.

The invention also provides a plant product stored at typical sub-zero frozen food storage temperatures, which has been previously partially dehydrated and to which at least one water activity control substance has been added, comprising: has water activity (measured at 20°C) and has a lower moisture content than unpreserved vegetable products;
and a vegetable product characterized in that both its water activity and its water content are in a range such that it remains flexible and unfrozen at typical sub-zero frozen food storage temperatures.

As used herein, the term "freezing" means that ice crystals and/or solute crystals are formed in the product;
Thus, it refers to a condition that makes it hard and/or brittle. It is an object of this invention to provide a product that does not "freeze" in this way at typical freezer temperatures.

In one preferred embodiment, the water activity of this invention is about 0.
less than 90, more preferably less than about 0.85. Water activity may be about 0.5 or higher, preferably about 0.7 or higher. Water activity is measured at 20°C. The actual value for the water activity limit will depend on the type of plant selected, as well as on factors such as the type and amount of water activity control substance added, and the water content of the selected plant.

The moisture content is chosen such that the botanical product remains flexible at typical frozen storage temperatures. The moisture content is preferably about 20-50%. More preferably, the moisture content is about 25-45%.

The final forms of botanical products produced by this invention include sliced plants, uncut or roughly cut leafy vegetables, and other forms of prepared plants. These plant products are stable at low temperatures, can be stored for short periods of time at temperatures above those typically used for normal frozen plant storage, do not spoil easily, and freeze solid. Never. Also, they do not freeze or become brittle at normal freezer temperatures. Generally, a suitable typical frozen food storage temperature is about -20<0>C.

Water activity and water content are influenced by adjustment of the composition of the plant by a combination of dehydration and addition of one or more water activity control substances. Water activity control substances include, but are not limited to, sodium chloride and other salts, sugars such as sucrose, dextrose and invert sugar, as well as polyhydric alcohols such as glycerol.

Prior to the introduction of the solute, the plant to be treated can be peeled, bleached or otherwise treated according to conventional methods and then dried, for example in air or in a vacuum. The solute can be prepared by any method including, but not limited to, pre-soaking before or after drying, tampling with a known amount of solute before drying, tampling with a solution or solid solute at an initial or intermediate stage. .

Further, the solute may be, for example, Australian Patent No. 53241
4, by (a) partially dehydrating the plant in air or vacuum; (b) at an appropriate stage;
IFJ or higher water activity controlling solutes can also be added to the plants by introducing them into the plants and (c) dehydrating the treated plants to the desired water content.

Alternatively, the water-active substance can be added before or simultaneously with the plant pieces being dehydrated. For example, add salt,
It can be briefly mixed with plant pieces to coat the pieces, which can then be dehydrated in air or vacuum.

Suitable water activity controlling solutes include sodium chloride, sodium citrate, potassium chloride and other similar salts, sugars such as sucrose, dextrose and invert sugar, and polyhydric alcohols such as glycerol, sorbitol or propylene glycol. including but not limited to. If sugar or saccharide is chosen as the water activity control substance, the total added sugar concentration in the final product is preferably 15% by weight or less so that the plant product has an acceptable taste.

The concentration of the above solute is determined by consideration of flavor, the nature of the solute,
Depends on variables such as the type of plant to be treated.

As used in this specification, the term "plant" refers to plants and plant parts that are normally considered plants, including leaves,
Petioles, roots, bulbs, corms, tubers, etc., as well as tomatoes,
Includes fruits such as squash and capocha and seeds such as corn and beans.

The definition of plant also includes mixtures of different plants.

Water activity depends on the amount of water present and the amount of other substances present in the food. The expression rawJ is used to describe water activity and is calculated with the formula % (where p is the vapor pressure of the food product and po is the vapor pressure of water at the same temperature).

The final composition of the botanical product is determined by the selection of the type and concentration of solutes added to the plant and by ensuring that the product does not freeze when the botanical product is subjected to subzero temperatures as low as 120°C. The moisture content of the treated plants, which ensures non-freezing, varies depending on the concentration of solutes added and the nature of the solutes, ranging from 20 to It can be on the order of 50%.

Generally, the higher the concentration of solute, the lower the water content at which the plant product will freeze. If the water content is too low compared to the added solute, the plant product will become hard, brittle, and weak at freezing temperatures due to crystallization of the solute. If the water content is too high compared to the solute, the plant pieces will freeze solid due to the formation of ice crystals, the cell structure will be damaged, and the plant pieces can become brittle and blocky.

The vegetable products produced according to this invention are flexible once the dehydration process is complete and remain flexible when held at the freezer temperatures at which they are to be stored. Furthermore, by reasonable selection of solutes and final water content, preferably the +
Water activity at 20°C is 0.9 or less, preferably 0.
It can be adjusted to a level below 85 and a level above 0,5. At such water activity levels, even if the temperature of the botanical product exceeds zero, the botanical product is not subject to bacterial degradation, nor is it subject to microbial degradation at anything other than a very slow rate. Storage at low temperatures is
Prevents changes in color and flavor and significantly extends shelf life.

The non-freezing dehydrated plant products of this invention have substantially higher water content than conventional dehydrated plants and generally have higher water contents than the solute-loaded plants described in Australian Patent No. 532414. have Therefore, the plant products of this invention require less processing time, are less susceptible to heat damage, and require less energy for dehydration.

Although these non-freezeable plant products may contain relatively high levels of added water activity control substances, they are typically removed by rehydration and cooking with a substantial volume of water in a ratio of about 10:1. prepared for use. This gives the salt and sugar levels in the product such that they are well within normal seasoning levels. Furthermore, these products
Rehydrate faster. They have a higher water content than normal dehydrated plants and the presence of solutes induces more rapid absorption of water into the plant tissues.

[Examples] Examples of the present invention will be shown below, but the present invention is not limited thereto.

Example 1 Spinach leaves with 7% total solids were washed to remove sand and dirt and roughly cut into strips approximately 5 cm wide. This was dehydrated to about 40% moisture. This spinach portion was mixed with salt and sugar in a tumbler for 3 minutes. The amount of solute is water 60%, 55%, 45%, 30%,
A final content of 5% salt and 10% sugar was calculated at 20% and 15%.

The final product had the following composition:

Sample Water activity Moisture % Freezing at -20℃ 1 0
．． 91 80 Yes 20.895
5 Yes 30.8643 No 4 0.75 28 No 50.5
817 No 60.4014 Yes Samples 3.4 and 5 had a soft texture and rehydrated quickly when covered with boiling water to give spinach with excellent flavor, color and texture. The leaf pieces were in the same whole large piece on the street before dehydration.

Example 2 Leaves of curleF parsley were removed from the stems and washed with water. Total solids content was 8%. these,
Tampled in portions with micronized salt and sugar. The added salt and sugar are 55%, 45%, and 35% moisture.
, 30% and 20% such that the final product contained 10% added salt and 10% added sugar.

This parsley was dehydrated until it reached a predetermined moisture content.

The final product had the following composition:

Base 1-Illusion 9-1 Bon! 10.9054 at -20℃
None 20.8748 None 30.7935 None 40.7582 None 50.6219 One frozen sample 1 to 4
was flexible in whole leaf form, had excellent color, and immediately rehydrated into a product with a fresh parsley aroma upon soaking in hot water.

Example 3 Fresh Savoy cabbage was chopped and soaked in boiling water for 3 minutes.
Drained. The total solids content of the drained cabbage was 6%.

The drained and bleached cabbage was divided into four 500 g portions and tampled with finely divided salt and sugar for 3 minutes to obtain an intimate mixture. The amount of salt and sugar added to each portion was determined by the final moisture content j 160%, 45%, 35%, 25
% and 15%, the added salt content was 5% and the added sugar was 5%. The minced meat was dehydrated to a weight calculated to provide the required moisture content. The final product had the following composition:

! Freezing at -20℃ 10
゜9268 Yes 2 0J4 42 No 3 0
．． 80 33.5 None 40.732
5 Partially frozen 50.4312 Samples 2 and 3
was flexible at -20°C and rehydrated within 5 minutes when covered with boiling water to give a product with excellent natural color, aroma and texture.

Example 4 Fresh carrots were manually peeled and chopped into 3 mm x 3 mm pieces. The shreds were exposed to steam for 3 minutes, at which point they had a total solids content of 8%.

Sufficient glycerol was thoroughly mixed with the bleached shreds so that the final product contained 10% glycerol at a moisture content of 30%. The chopped pieces were then dried at 70° C. to a predetermined moisture content of 30%. Dry shreds containing 10% glycerol remained quite flexible at -20°C.

Water activity was 0.71. When boiled in 20 parts by weight of water, they were soft, fully rehydrated within 3 minutes, and had good color and texture.

Example 5 Several additional plants were preserved according to the invention. The results are shown in Figures 1 to 9 and listed in the table below.

Plants were treated with a salt (NaCl) solution containing 5% added NaCl with the moisture described below. This plant was at a temperature of -20°C.

In the drawing, the symbol 0 indicates that the process freezing was successful;
According to the invention, the plant remains flexible at 120°C, indicating that it did not freeze, and is marked with the symbol
indicates an unsuccessful result, indicating that the plant was frozen solid.

FIG. 1 shows the results of preserving sliced potatoes according to the invention as shown in the table below:
Ru.

Sample Water activity (A w ) Moisture % Freeze solid? 1
0.92 43 Yes2 0
．． 87 38 No 3 0.8
0 25 No 4 0.78
22 No 5 0.73
18 No 6 0.88
15 Yes7 0.84 14
Figure 2 shows the results of storing spinach as shown in the table below.

Group 1 Water activity (A w ) Freeze solid? 1
0.90 55 Yes 2 0,
H52 Yes 3 0.83 40 No 4
0.82 32 No 5 0
．． 80 80 No 6 0.7
2 28 No 7 0.58
18 Yes Figure 3 shows the results of storing chopped carrots as shown in the table below.

1 0.86 46 Yes2
0.82 40 No 3 0.
81 87 No 4 0.77
33 No 5 0.71
27 No 6 0, H20 No 7 0.53 18 Yes Figure 4 shows the results of storing sliced zucchini as shown in the table below.

■statement 2+ko W) 1Lyago1XJ1yu1G,
87 49 Yes2 0.83
42 No 3 0.82
41 No 4 0.76
34 No 5 0.73 3
0 No 6 0.84 27
No 7 0.51 19
Figure 5 shows the results of storing green peas as shown in the table below.

Sample Water activity (Aw) Moisture % -1<Fast"Lyu1
0.91 53 Yes2 0
．． 88 36 No 3 0.7
9 27 No 4 0.78
24 No 5 0.72
21 No 6 0.67
17 Yes7 0.62 14
Yes Figure 6 shows the results of storing diced tomatoes as shown in the table below.

Sample Water activity (A w ) Moisture % Freeze solid? 1
0.71 81 No 2
0.65 28 No 3 0.
56 26 No 4 0.52
23 No 5 0.49
20 Yes Figure 7 shows the results of preserving green onion tops as shown in the table below.

Sample Water activity (Aw) Moisture % Freeze solid? 1
0.88 59 Yes2 0.8
4 51 No 3 0, H46
No 4 0.68 28 No 5
0.49 14 Yes Figure 8 is
The results of preserving Green Bell Peraper as shown in the table below are shown.

Figure 9 shows the results of storing sliced onions as shown in the table below.

Sample Water activity (A w ) Moisture % Freeze solid? 1
0.94 67 Yes2 0
．． 91 53 Yes3 0.88
41 No 4 0.83
25 No 5 0.81.
15. The above description is only an illustration of the present invention, and it is obvious that changes and modifications can be made without departing from the gist of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 9 are graphs showing the effects of the present invention. 1 0.87 2 0.82 3 0.70 4 0.58 5 0.40 60 Yes 49 No 34 No 20 Yes 13 Yes Applicant's agent Patent attorney Suzue Takehiko%〃2O N %H20 To\ (u %/-/20 %H20 %y2゜%l-/, Q 笥＼ %H,0 %H,0

Claims (12)

[Claims] (1) A method for preserving a vegetable product at subzero temperatures, the method comprising first treating the product by partially dehydrating and adding at least one water activity control substance to the product; with a water activity of less than 1 (measured at 20°C) and a water content lower than that of the untreated vegetable product;
and the water activity and water content are both in a range such that the product remains flexible and unfrozen at typical sub-zero frozen food storage temperatures; A method comprising lowering to storage temperature. 2. The method of claim 1, wherein said water activity controlling substance is added at the same time as or before said product is partially dehydrated. 3. The method of claim 1, wherein the product is dehydrated prior to addition of the water activity control substance. 4. The water activity of claim 1 is in the range of about 0.5 to about 0.9 (measured at 20°C) and the water content is in the range of about 20 to about 50%. Method. (5) the water activity is within the range of about 0.7 to about 0.85 (measured at 20°C), and the water content is about 25 to about 45%;
2. The method of claim 1 within the scope of. (6) The method according to claim 1, wherein the water activity controlling substance is selected from one or more of sodium chloride, sodium citrate, potassium chloride, sucrose, dextrose, invert sugar, glycerol, sorbitol, and propylene glycol. 7. The method of claim 1, wherein the typical frozen food storage temperature is about -20<0>C. (8) A plant product stored at typical subzero frozen food storage temperatures that has been previously partially dehydrated and to which at least one water activity controlling substance has been added, the plant product having a water activity ( (measured at 20°C) and has a lower moisture content than unpreserved vegetable products, and both water activity and moisture content ensure that the product is flexible at typical sub-zero frozen food storage temperatures. A vegetable product characterized in that it exists in an unfrozen state. (9) The water activity of claim 8 is in the range of about 0.5 to about 0.9 (measured at 20°C) and the water content is in the range of about 20 to about 50%. plant products. (10) The water activity is in the range of about 0.7 to about 0.85 (measured at 20°C), and the water content is in the range of about 25 to about 45
9. A botanical product according to claim 8, within the range of %. (11) Claim 8 wherein the water activity controlling substance is selected from one or more of sodium chloride, sodium citrate, potassium chloride, sucrose, dextrose, invert sugar, glycerol, sorbitol, and propylene glycol.
Botanical products listed. 12. The plant product of claim 8, wherein the typical frozen food storage temperature is about -20°C.