JPS63230036A - Preservation of vegetables - Google Patents

Abstract

PURPOSE:To keep the freshness of raw vegetables high by dipping them in a buffer solution of a specific pH at low temperature, removing the solution from them and storing them in a cool place. CONSTITUTION:Raw vegetables, preferably cut vegetables or young seedling vegetables are treated with a buffer solution of a pH adjusted to about 5.3, preferably an acetate, citrate or phosphate buffer system at low temperature. Then, the vegetables, after the solution is removed, are stored in a cool place.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a method for preserving vegetables that maintains their freshness for a long period of time, by soaking them in a buffer solution with a pH value within a specific range that is harmless to humans and animals. It is characterized by

(Conventional technology) In recent years, when it comes to eating habits, at the same time as seeking deliciousness,
The need for convenience, such as ease of purchase and handling, is increasing. This can also be said about vegetables, including the complexity of cooking and the disposal of vegetable waste after cooking.In order to be convenient and economical, cut vegetables, dried vegetables, frozen vegetables, canned vegetables, etc. There is a growing trend toward seeking already processed vegetable products such as vegetables. However, fresh vegetable labels such as cut vegetables and seed vegetables lose their freshness quickly, especially during the distribution process, and maintaining freshness for a long period of time is a big advantage.

In order to deal with this situation, various methods have been proposed to maintain the freshness of fresh vegetables. However, as a method to remove residual chlorine after treatment, which is a disadvantage of this method, a method of washing with a reducing agent such as sulfite after treatment with a chlorine-based disinfectant has also been proposed. There is. (Japanese Unexamined Patent Publication No. 104773/1983). Furthermore, as mentioned above, a method of blanching vegetables by treating them with a mixed solution of acetic acid and acetate at 60 to 100°C for a short period of time has been proposed as a method of processing vegetables without using chlorine-based disinfectants. There is. (Unexamined Japanese Patent Publication No. 58-162254).

(Problems to be Solved by the Invention) In the vegetable processing method disclosed in JP-A No. 61-104773, the use of chlorine-based disinfectants is essential, and residual sterilization must be erased with a reducing agent. However, in some cases, there is a concern that trace amounts of chlorine may remain even after such treatment.
In the method disclosed in Publication No. 54, blanching is performed with a mixed solution of acetic acid and acetate without using a chlorine-based disinfectant, and in this case, there is no growth of microorganisms after the processed vegetables are processed. Because of this, the mixed solution is heated for a short time at a temperature of 60 to 00° C., but such a treatment method cannot be applied when preserving fresh vegetables in their raw form.

(Means for Solving the Problems) This invention was made in view of the above-mentioned circumstances, and the inventors have proposed to improve the freshness of the food by treating it with a processing agent that does not affect the taste at all and is harmless to humans and animals. Research on a method for preserving fresh vegetables at a low temperature in a buffer solution adjusted to a pH value of 5.3 to 5.7, followed by removing the adhering liquid and storing it in a cool place, resulted in long-term preservation. It was possible to obtain good quality fresh preserved vegetables that do not lose their freshness even after storage and have the same taste as before processing.

(Function) Vegetables to which this invention applies include leafy vegetables, root vegetables, stem vegetables, etc.
The types are not particularly limited, but cut colored or pale vegetables such as lettuce, cabbage, carrots, green peppers, burdock, daikon radish, green onions, and onions, which tend to be particularly problematic in recent years in terms of quality maintenance because of their rapid damage over time. Vegetables and seed vegetables such as bean sprouts such as mung beans, soybeans, and daikon radish are suitable.

In these cut vegetables, the cellular Mi fibers are destroyed due to the exposure, and the ffl texture of bean sprout seed vegetables is soft, making them more susceptible to microbial attack, and contamination caused by this causes a rapid decline in freshness. As a result, quality deterioration increases.

The inventors conducted various studies on preserving freshness by fully considering the properties and distribution conditions of the vegetables mentioned above, and found that vegetables were immersed in a buffer solution adjusted to a selected specific range of pH value at low temperature, and then stored in a cold place. It has been found that by using a simple preservation method, the product maintains its freshness well even during storage for approximately one week during the distribution process. This invention was made based on this knowledge.

The chemicals used in the preparation of the buffer solution with a pH value of 5.3 to 5.7 used in this invention are harmless to humans and animals and easily water-soluble.
There are no particular restrictions on the type of vegetables as long as they do not leave any off-taste or odor on the vegetables after processing and can be easily removed by draining by centrifugation, etc., but organic acids such as acetic acid and citric acid Acid-based and inorganic acid-based such as phosphoric acid are preferred, and at least one selected from these is preferably prepared. In addition, it is desirable that the concentration suitable for the treatment be as dilute as possible, preferably in the range of 0.05 to 0.5 mol/liter, and the treatment temperature should be low as long as it does not damage the vegetables, but The range is 5-15°C. The soaking time should not be longer than necessary and should be adjusted in consideration of the physicochemical properties and freshness of the target vegetables, but should be in the range of 1 to 5 minutes.

Vegetables soaked under the above conditions are then drained to remove the adhering liquid, but it is safe to put them in a net bag or the like and perform centrifugal dehydration to avoid mechanical damage. Vegetables that have been drained should be stored in a cool place, preferably at 1 to 10°C, but packaging materials such as plastic bags may also be used. With this storage method,
To enable good preservation without losing freshness for one week or more.

Although it is not clear why vegetables, especially cut vegetables, can be stored for long periods of time without losing their freshness as mentioned above,
By setting the pH value within a very limited range of 5.3 to 5.7, the surface area of vegetables.

This PE (because it is buffered in the area, the activity of the attached microorganisms is suppressed and their proliferation does not proceed, and the proteins that make up the cell tissue, including the destroyed cells located on the thin surface, are not denatured, etc.) By the way, as explained in the test example below, a pH value range of 5.8 to 9 is optimal for microorganisms to grow, and discoloration due to proliferation occurs, and furthermore, at high alkalinity, the microorganisms themselves Although the growth of microorganisms can be suppressed, it is not difficult to predict that cell tissue destruction 1 dye leakage will occur.On the other hand, at a pH value of 5.2 or less, microorganism growth and proliferation can be suppressed, but the tissue will become soft due to the acid. A pH value outside the range of 5.3 to 5.7 cannot be used because pickling is promoted.

This invention is as described above, and will be explained with test examples.

Test Example 1 Cut cabbage was prepared by shredding 3.5 kg of fresh cabbage immediately after harvest using a vegetable cooking machine.
00g was taken as the initial sample and the remaining was divided into approximately 7 equal parts. One section was packed into a plastic bag for the untreated section, and the remaining six sections were immersed in buffer solutions with pH values of 4.5, 5, 5, 6.7 and 9 for 5 minutes at 15°C, and then placed in a nylon net bag. Pack it, centrifuge dehydrate it, pack it into a plastic bag, seal it, and store it at 8℃.
The cells were stored in a controlled incubator for 7 days. In this case, the buffers with pH values 4.5 and 5.5 are acetic acid buffer solution (0.2 mol/l), pH values 6 and 7
The buffer is a phosphate buffer (0.1 mol/liter) and the PHHO2 buffer is a carbonate, bicarbonate buffer (0.1 mol/liter).
, 1 mol/liter) was used.

Initial and preserved samples collected when shredding cabbage 7
Table 1 shows the number of bacteria and their properties (according to the naked eye) after several days.

The number of bacteria is measured using the standard agar medium method (37
℃, 48 hours), and the number of coliform bacteria was determined using the desoxycholate medium method (37℃, 20 hours). Even after 7 days of storage, it retains its freshness, and the number of killed bacteria and coliform bacteria are both numerically lower than those at the initial stage, and the growth of these microorganisms is completely suppressed. When I ate the preserved cut cabbage, there was no taste of the chemicals used in the buffer solution, and even when I ate it, the texture and taste were just like that of Sumitomo. In the untreated area and the treated area with a pH value of 6 or higher, discoloration such as yellowing or browning occurs after 2 days, and the discoloration progresses as days pass, and this tendency is P
The higher the H value, the more pronounced this becomes. On the other hand, in the treated area with a pH value of 4 or less, whitening occurred after 2 days and progressed over time, and on the 7th day, outflow of tissue cell fluid was observed, a strong acid odor was observed, and the pickles were completely removed. state.

Test Example 2 Since it was known from Test Example 1 that only 5.5 is effective as a treatment PH value, the vicinity of the PH value of 5.5 was further subdivided and a similar test was conducted.

3.8 kg of fresh cabbage was prepared according to the procedure of Test Example 1 for initial sample, untreated area, and pH value 5.0 to 6.0 (
0.1 increments) Prepare cut cabbage for medical use, and soak each cut cabbage for medical use in a buffer solution with a test pH value of 10.
After soaking for 5 minutes at
The cells were stored in a controlled incubator for 8 days. Table 2 shows the number and properties of bacteria at the initial stage and after 8 days of storage.

Note that a citric acid buffer solution was used as the buffer solution.

As can be seen from Table 2, P can be adopted as a processing condition.
The H value ranges from 5.3 to 5.7, and if it is above or below this range, the properties of the preserved vegetables will be similar to the results shown in Table 1, and quality deterioration will occur.

From the results of Test Examples 1 and 2 above, it is known that the range of pH values that can suppress the growth of microorganisms and maintain freshness is within a very narrow range of 5.3 to 5.7. The method is characterized in that vegetables are immersed in an aWR solution of a certain amount.

Test Example 3 As described above, the pH value of the buffer solution was set to 5.3 as the storage condition.
It was found that the range of 5.7 to 5.7 was sufficient, but further tests were conducted in which the target vegetables and drugs were changed. Three types of green peppers and carrots were prepared and shredded into cut vegetables in the same manner as Test Example 1, and mung bean sprouts were prepared, and three types of buffer solutions with a pH value of 5.5 were prepared according to the procedure of Test Example 1. These test vegetables were soaked, and after removing water, they were placed in a plastic bag and sealed.
It was stored in an 8°C incubator for 6 days. The results are shown in Table 3.

As can be seen from Table 3, - The number of sterilized bacteria and the number of coliform bacteria vary slightly depending on the type of vegetables, but since the properties of vegetables maintain their freshness after storage, it depends on the type of chemicals used. Preservability is almost unaffected.

As is clear from the above test examples, the main feature of the preservation method of this invention is that vegetables are treated with a buffer solution whose pH value is adjusted to a very limited range of 5.3 to 5.7. As long as these conditions are met, good storage stability can be ensured without damaging the vegetable cell tissue.

Table 3 with blank space below (Example) Example-1 After removing the outer skin and core of 8 fresh cabbages directly from the farm, they were shredded into strips using a vegetable cooking machine.
kg of cut cabbage was obtained. This was placed in an immersion tank with a stirring blade containing 10 liters of a citric acid buffer solution (10°C, 2 mol/liter) adjusted to a pH value of 5.
After being immersed for 5 minutes while stirring very slowly, it was taken out, packed in a cloth bag, and dehydrated for 30 seconds in a centrifugal dehydrator. The dehydrated cut cabbage was packed in a 10 liter plastic bag and stored in a refrigerator (4 to 6°C). When I took it out after one week of storage, it was discolored.

There is no problem with phenomena such as softening, and the freshness is maintained, and the texture such as texture is satisfactory when eaten raw, and the taste is not at all interesting. there were. The microbial counts of the cut cabbage before treatment and after storage were summarized in Table 4.

Example-2 Approximately 5 pieces of cut cabbage prepared in the same manner as Example 1
kg with PH value, acetate buffer adjusted to 5 (10 °C, 0
．． 2 mol/liter) was placed in a dipping tank with a stirring blade for 10 liters, and after immersion for 5 minutes while stirring very slowly, it was taken out, packed in a nylon net bag, centrifugally dehydrated, and then placed in a plastic bag (capacity 10 liters). Packed 8±2
It was stored in a constant temperature room controlled at ℃. When taken out after one week, there was no deterioration phenomenon such as discoloration or softening, and the freshness was maintained well, and when eaten, there was no sour taste or sour odor at all, and the taste was good. The microbial counts of the cut cabbage before treatment and after storage were summarized in Table 4.

Example-3 2k of soybean sprouts immediately after harvest soaked in a water tank at about 10'C
Drain the g on a net and add it to the PH value.

Citrate buffer solution adjusted to 3 (10°C, 0.2 mol/
liter) Transfer to a plastic bucket containing 10 liters and soak for 3 minutes while stirring gently by hand. Transfer this to a cloth bag and centrifugally dehydrate it. Transfer this in portions to 500 cc capacity plastic dishes and cover with saran wrap at a temperature of 8 ± 2 ° C. Stored in a controlled cold room. When taken out after one week, no deterioration such as discoloration or softening was observed, and the freshness was maintained well.

The microbial counts of the bean sprouts before treatment and after storage were as summarized in Table 4.

Table 4 (Effects of the Invention) According to the preservation method of the present invention, good preservation can be achieved with high accuracy using a very simple method of immersing the product in a buffer solution adjusted to a pH condition within a limited range and then storing it in a cool place. This enables the prevention of quality deterioration due to loss of freshness of vegetables during the distribution stage, increasing product value, and eliminating the use of conventional chlorine-based disinfectants that may remain on vegetables and deteriorate their taste. First, the chemicals used are harmless to humans and animals, so they are safe, and highly fresh vegetables can always be supplied to the market and to the dining table, greatly contributing to the distribution and consumption of vegetables.

Claims (3)

[Claims] (1) A method for preserving vegetables, which comprises immersing fresh vegetables in a buffer solution adjusted to a pH value of 5.3 to 5.7 at a low temperature, removing the adhering liquid, and storing the vegetables in a cool place. . (2) The method for preserving vegetables according to claim (1), wherein the fresh vegetables are cut vegetables or seed vegetables. (3) The method for preserving vegetables according to claim (1) or (2), wherein the buffer solution is at least one selected from acetic acid, citric acid, and phosphoric acid.