JP2003333987A - Method for keeping freshness of cut vegetable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for sterilizing bacteria attached to cut vegetables and achieving high sterilizing effect unattainable by a conventional sterilization method to immerse cut vegetables in a solution having low pH. <P>SOLUTION: The method for sterilizing cut vegetables in a sterilizing solution with improved sterilizing effect comprises the 1st sterilization to immerse the cut vegetables in a fumaric acid solution containing dissociated hydrogen ion and the 2nd sterilization to take the cut vegetables out of the fumaric acid solution and immerse the vegetables coated with the fumaric acid solution in a solution of sodium hypochlorite. A chemical reaction to substrate a hydrogen ion (H<SP>+</SP>) with a sodium ion (Na<SP>+</SP>) takes place in the 2nd sterilization step to form hypochlorous acid (HClO) having extremely high sterilization power. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of keeping freshness of cut vegetables for keeping the freshness of cut vegetables for a long time.

[0002]

2. Description of the Related Art In recent years, demand for cut vegetables (eg, mixed salad, coleslaw salad, etc.) cut into a size and shape according to the purpose has been increasing due to convenience in using fresh vegetables. It is difficult to maintain the freshness of cut raw vegetables for a long time, and it is the current situation that the fresh vegetables generally have a shelf life of about 1 to 2 days after production. Therefore, this type of cut vegetables is a product that has a very troublesome production amount control and inventory control and has a high disposal rate due to expiration of the expiration date. The freshness of the cut vegetables includes a sensory part such as odor, color, appearance and taste, and a hygiene part due to the number of attached bacteria.

[0003] This type of cut vegetables is commercially available in a packaged state, but as one of the factors that reduces the freshness of the cut vegetables, spoilage due to bacteria is raised. That is, the more bacteria attached to the cut vegetables, the faster the decay progresses.

As a method for reducing the number of bacteria attached to cut vegetables, conventionally, cut vegetables are soaked in a low pH solution to sterilize the attached bacteria, and the number of bacteria at the initial stage (stage before packaging) is reduced. The method of reducing is adopted. Additives that can be used in food include organic acids such as acetic acid, lactic acid, gluconic acid, succinic acid, malic acid, tartaric acid, citric acid, phytic acid, and fumaric acid (there are many other types). In addition, chlorine-based ones such as sodium hypochlorite are also widely used.

The inventors of the present invention have conducted various tests on a method for keeping freshness of cut vegetables for a long period of time.
It was confirmed that even a simple immersing in H solution (for example, fumaric acid solution) or chlorine-based solution (for example, sodium hypochlorite solution) had a considerable sterilization effect. For example, when tested on Chinese cabbage that had been cut into pieces, the number of general bacteria before treatment was 6.06 log CFU / g as an average logarithmic value, but after soaking in a fumaric acid solution (concentration 2000 ppm) for 10 minutes, the average The numerical value decreased to 2.30 log CFU / g, and the average logarithmic value decreased to 2.75 log CFU / g after being immersed in a sodium hypochlorite solution (concentration: 200 ppm) for 10 minutes.

On the other hand, in recent years, MA (Modified Atmospher)
e) A method of storing fruits and vegetables in a low oxygen and high carbon dioxide state called packaging is being developed. What is this MA packaging?
By balancing the breathing of fruits and vegetables themselves with the permeation of gas in the packaging bag, keep the oxygen concentration and the carbon dioxide concentration at approximately 5 to 15%, respectively, and limit the breathing volume of fruits and vegetables (in hibernation state) The storage method is designed to slow down the speed of quality deterioration. In the test example, 150 g of coleslaw salad (121 g of chopped cabbage, 12 g of chopped cucumber, 12 g of chopped carrot) were each packed in a normal sealed package (vacuum pack) and MA package, respectively.
When stored at 0 ° C., the sealed package showed a change in odor after 1 day, whereas the MA package showed a change in dryness and odor after 6 days. That is, in the hermetically sealed package, the inside of the bag becomes anoxic (or an extremely low concentration of oxygen) in a relatively short time by breathing cut vegetables,
It is considered that the decay of cut vegetable cells progresses rapidly, and in MA packaging, on the other hand, the inside of the bag is aged when the cut vegetable cells enter the prescribed low oxygen / high carbon dioxide state that causes hibernation. It is considered that the deterioration of quality can be delayed by suppressing the progress of If the cut vegetables are left unpackaged (exposed to the atmosphere), the cells actively breathe to promote aging and to release water, which further deteriorates the quality. In the above test example, M
As a packaging material for A packaging, "Sumitomo Bakelite Co., Ltd."
Trade name; P-Plus "was used.

[0007]

By the way, in the cut vegetables, the freshness in terms of the sensory aspect was able to secure a considerable number of days of freshness retention (7 days) by the above MA packaging, but the number of bacteria attached to the cut vegetables was as high as possible. It is preferable to reduce the amount.
That is, in the above test example, the number of bacteria was reduced to 2.30 log CFU / g as an average logarithm when immersed in a fumaric acid solution, and the average number of bacteria was decreased when immersed in a sodium hypochlorite solution. The logarithmic value decreased to 2.75 log CFU / g, but further sterilization is desired from the viewpoint of hygiene. In the following description, the number of bacteria attached to the cut vegetables before being enclosed in the storage bag may be referred to as the initial number of bacteria.

[0008] Therefore, the present invention provides a method for keeping freshness of cut vegetables, in which the freshness of the cut vegetables, particularly the number of initial bacteria adhering to the cut vegetables is further reduced and the sterilized state can be stored for a long time. It is intended to be provided.

[0009]

The present invention has the following constitution as means for solving the above problems.

The present invention is directed to a method of maintaining the freshness of cut vegetables, and in particular, is intended to maintain the freshness of cut vegetables for a long time by reducing the number of bacteria adhering to the cut vegetables. . Then, the freshness preservation method of the present invention is performed as follows.

Vegetables include Chinese cabbage, cabbage, lettuce,
Radish, cucumber, carrot, leek, bell pepper, onion and the like can be used, and one kind or a plurality of kinds can be selected from these and used. In addition, these vegetables are cut into a shape according to the purpose (for example, chopped, shredded, chopped, etc.). The number of bacteria (viable bacteria) attached to the cut vegetables is often about 4 to 7 log CFU / g as a logarithmic value, depending on the type of vegetables and the degree of washing with water.

Then, in the present application, first, the cut vegetables are immersed in a fumaric acid solution for primary sterilization. Fumaric acid has hydrogen ions (H ⁺ ) dissociated in the state of an aqueous solution, but the higher the concentration of fumaric acid, the lower the pH value.
The fumaric acid solution having a concentration of 1000 to 3000 ppm and a pH of about 2 to 3 can be used.
If the concentration of the fumaric acid solution is lower than 1000 ppm, the low pH range required when a large amount of vegetables are continuously treated cannot be maintained, while if it exceeds 3000 ppm, no significant improvement effect appears, so 3000 ppm Is enough. The dipping time of the cut vegetables in the fumaric acid solution is not particularly limited, but may be about 5 minutes.

As described above, when the cut vegetables are immersed in the fumaric acid solution, a considerable number of bacteria (viable bacteria) attached to the cut vegetables are killed (for example, when the cut vegetables are attached to the cut vegetables by a logarithmic comparison). 45 to 70% of the original bacterial count).

Next, the cut vegetables immersed in the fumaric acid solution are taken out. The fumaric acid solution remains attached to the surface of the cut vegetables taken out. Incidentally, hydrogen ions are dissociated in the fumaric acid solution adhering to the surface of the cut vegetables.

Next, the cut vegetables with the fumaric acid solution still attached are immersed in a sodium hypochlorite solution for secondary sterilization. This sodium hypochlorite solution is 50-2
It can be used at a concentration of 00 ppm. This sodium hypochlorite solution also has a fairly strong bactericidal power.

Since the sodium hypochlorite solution exerts a strong bactericidal force by a chemical change with hydrogen ions in the fumaric acid solution as described later, it has a relatively low concentration (50 to 20).
However, when the concentration of the sodium hypochlorite solution is lower than 50 ppm, the effect is weak and when the treatment is continuously carried out, the solution is diluted and the sufficient effect cannot be maintained. On the other hand, 2
Even if it exceeds 00 ppm, no remarkable improvement effect appears,
Up to ppm is sufficient. If the chlorine concentration is too high,
Even if the cut vegetables are washed with water after the treatment, a peculiar chlorine odor may remain, which is not preferable. The soaking time of the cut vegetables in the sodium hypochlorite solution may be about 10 minutes.

By the way, sodium hypochlorite (NaCl
O), when a hydrogen ion (H ⁺ ) is present nearby in an aqueous solution state, the hydrogen ion (H ⁺ ) is replaced with the sodium ion (Na ⁺ ) of sodium hypochlorite to give hypochlorous acid (H ⁺ ). HClO) is produced. That is, NaClO + H ⁺ → HC
A chemical change of 10 + Na ⁺ occurs.

Since this hypochlorous acid (HC10) has a much stronger bactericidal activity than that of sodium hypochlorite (NaClO), it has a function of strongly sterilizing bacteria (viable bacteria) remaining in cut vegetables. is there. In addition, hypochlorous acid (HClO) is
Since it is unstable and easily decomposed, it is difficult to maintain the state of hypochlorous acid in the solution for a long time. Therefore,
In the second sterilization, sodium hypochlorite (NaCl
It is not possible to directly use a hypochlorous acid (HClO) solution instead of the O) solution.

Next, the cut vegetables in the sodium hypochlorite solution are taken out, washed with water, and then drained. In this state, that is, the number of bacteria adhering to the cut vegetables in the state of being immersed in the fumaric acid solution → soaking in the sodium hypochlorite solution → washing with water → draining water is the untreated state. The number of bacteria (4-7 log CFU / g in logarithmic value) attached to the cut vegetables (as cut) was reduced to 30-40%.

After that, the drained cut vegetables are enclosed in a storage bag to obtain a final product (cut vegetables in a bag). Then, the cut vegetables in a bag are preferably distributed and stored at a low temperature of about 4 to 7 ° C. In addition, like this,
When stored at a relatively low temperature, it was possible to suppress the growth of bacteria remaining in the cut vegetables, and there was almost no growth of bacteria even after 7 days had elapsed.

Further, in the present invention, a packaging material capable of so-called MA packaging (for example, trade name: P-Plus manufactured by Sumitomo Bakelite Co., Ltd.) can be used as the storage bag. That is, this storage bag is an air-permeable material having a large number of fine pores (for example, a pore size of about 30 to 100 microns), and the oxygen concentration in the bag is 5 to 10 by breathing cut vegetables that are hermetically sealed. %, Carbon dioxide concentration is 10-15
It has a function of achieving an equilibrium state in%.

By the way, when cells of cut vegetables (raw vegetables) are kept in a hibernation state, aging occurs while the cells are alive.
It is known that the progress of decay can be suppressed, but in order to put the cut vegetable cells into hibernation, maintain an equilibrium state with an oxygen concentration of 5-10% and a carbon dioxide concentration of 10-15%. It is better to let them do it. Further, it is preferable to carry out the storage bag in a low oxygen / high carbon dioxide state in such a short time as possible. Use packaging materials that fit in.
This MA packaging does not affect bacteria adhering to the cut vegetables, but it is effective in maintaining freshness in terms of sensory elements (discoloration, soft rot, water floating, drying, odor, taste, etc.). is there.

[0023]

As described above, according to the method for maintaining freshness of cut vegetables of the present invention, hydrogen ions in the fumaric acid solution are cut after the cut vegetables are immersed in the fumaric acid solution (first sterilization). Since it is soaked (second sterilization) in the sodium hypochlorite solution while being attached to the vegetables,
In the sodium hypochlorite solution, hydrogen ions (H ⁺ ) and sodium hypochlorite (NaCl) in the fumaric acid solution were used.
A chemical change (NaClO + H ⁺ → HClO + Na ⁺ ) in which the sodium ion (Na ⁺ ) of O) is replaced occurs, and hypochlorous acid (HClO) having extremely strong bactericidal activity is generated therein.

Therefore, according to the present invention, the bactericidal power can be further enhanced by the action of the above-mentioned chemical change (generation of hypochlorous acid), rather than merely passing through the low pH solution twice, and the bactericidal effect is further enhanced as compared with the conventional case. The effect is that you can. or,
In this way, if the number of initial bacteria remaining in cut vegetables can be reduced, the number of bacterial growth in the preserved state can be proportionally suppressed, and the progress of decay due to the increase in the number of bacteria can be delayed and the preservation period can be extended. effective.

As a storage bag for packaging cut vegetables,
Use of so-called MA packaging material is effective in keeping freshness on the sensory side (discoloration, soft rot, floating in water, dryness, odor, taste, etc.) in cut vegetables with a reduced residual bacterial count as described above. Therefore, there is an effect that the freshness retention period as a whole can be lengthened.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. Example of the present application In this example, Chinese cabbage was used as a cut vegetable, and the root portion of a commercially available Chinese cabbage was cut to a diameter of about 3 cm.
Four outer leaves were removed and vertically divided into four equal parts. The number of general bacteria attached to this cut vegetable is 10 ⁵ to 1
0 ⁷ was CFU / g (6.06log CFU / g in average log value).

The fumaric acid solution was prepared by diluting a 30% fumaric acid stock solution 100-fold (fumaric acid 0.3% solution).
Was used. The pH of the fumaric acid solution at this time is 2.46, and a large amount of hydrogen ions are dissociated in the solution. still,
This fumaric acid solution was used at a liquid temperature of 20.6 ° C.

The sodium hypochlorite solution used had an effective chlorine concentration of 200 ppm. The sodium hypochlorite solution was used at a liquid temperature of 16.2 ° C.

In this example, first, the cut vegetables (divided vertically into four equal parts) are immersed in the fumaric acid solution (first sterilization). At this time, the bacteria adhering to the cut vegetables are sterilized by the bactericidal action of fumaric acid. Then, in this example, the cut vegetables are immersed in the fumaric acid solution for 5 minutes and then taken out from the fumaric acid solution. The fumaric acid solution remains attached to the cut vegetables taken out, and hydrogen ions in a dissociated state are present in the attached fumaric acid solution.

Next, the cut vegetables with the fumaric acid solution still attached are immersed in the sodium hypochlorite solution (second sterilization). At this time, hydrogen ions (H ⁺ ) in the fumaric acid solution adhering to the cut vegetables were replaced with sodium ions (Na ⁺ ) of sodium hypochlorite (NaClO), and hypochlorous acid (HC10) was changed. Is generated. That is,
A chemical change of NaClO + H ⁺ → HClO + Na ⁺ occurs. This hypochlorous acid (HClO) has a remarkably stronger bactericidal power than sodium hypochlorite and is produced near the surface of cut vegetables. Therefore, against the residual bacteria remaining in the cut vegetables, in addition to the bactericidal power of sodium hypochlorite, a strong bactericidal power of hypochlorous acid acts, and it cannot be sterilized by sodium hypochlorite alone. The number of remaining bacteria can be reduced to the range. In addition, hypochlorous acid (HClO)
Since it is very unstable and decomposes immediately, it is impossible to always prepare a solution containing hypochlorous acid. Therefore, the above-mentioned primary sterilized cut vegetables cannot be directly immersed in the hypochlorous acid-containing solution. The cut vegetables were immersed in the sodium hypochlorite solution for 10 minutes.

Next, the sterilized cut vegetables were taken out from the sodium hypochlorite solution, washed with water (replacement of stored water 3 times), and drained by a centrifugal method. When the number of general bacteria remaining in the cut vegetables in this state was tested with 3 samples,
Average logarithmic value is 2.00 log C in the range of 10 ¹ to 10 ³ CFU / g
It was FU / g.

This cut vegetable that has been continuously sterilized has about 1
Each 5 g was put in a stomacher bag and sealed, and 6 bags each were stored at 4 ° C. and 7 ° C. And after 3 days and 7
When the number of general bacteria in each cut vegetable (3 samples each) stored at each temperature when the day passed was examined,
The following results were obtained. After 3 days, if stored at 4 ℃, out of 3 samples,
Two were below the detection limit and the average logarithmic value was 1.28 log CFU / g
Met. The detection limit is 10 CFU / g. After 3 days, if stored at 7 ℃, out of 3 samples,
One is below the detection limit and the average logarithmic value is 1.20 log CFU / g
Met. After 7 days, 3 samples will be 1 if stored at 4 ° C.
The average logarithmic value is 1.42 log C in the range of 0 ¹ to 10 ² CFU / g.
It was FU / g. After 7 days and stored at 7 ℃, 3 samples are 1
The average logarithmic value is 2.09 log C in the range of 0 ¹ to 10 ³ CFU / g.
It was FU / g.

Looking at the results of these tests, although there were some variations depending on the sample, the number of detected bacteria was found in each sample up to 3 days at each temperature and 7 days after storage at 4 ° C. (above). Is much lower than the initial bacterial count (average logarithmic value of 2.00 log CFU / g), and the hygiene quality is further improved. Also, even after 7 days of storage at 7 ° C (above), it is almost the same as the initial number of bacteria,
It can be seen that high quality is maintained in hygiene. Comparative Example 1 As the cut vegetables, the above-mentioned Chinese cabbage was used, which was cut and not sterilized (untreated) was put in a stomacher bag at a rate of about 15 g and sealed at 4 ° C. as in the case of the present Example. 6 bags were stored at 7 ° C. Then, the number of general bacteria of the cut vegetables (3 samples each) stored at each temperature after 3 days and 7 days was examined, and the following results were obtained.

The initial bacterial count of unprocessed cut vegetables is
Three samples had an average logarithmic value of 6.06 log CFU / g in the range of 10 ⁵ to 10 ⁷ CFU / g. After 3 days, the samples stored at 4 ° C. had an average logarithmic value of 5.80 log CFU / g in the range of 10 ⁵ to 10 ⁷ CFU / g. After 3 days and stored at 7 ° C, 3 samples have 10 ⁵ to 10 ⁷ C
The average logarithmic value was 5.96 log CFU / g in the range of FU / g.
After 7 days, 3 samples will be 1 if stored at 4 ° C.
The average logarithmic value is 5.80 log C in the range of 0 ⁵ to 10 ⁷ CFU / g.
It was FU / g. After 7 days and stored at 7 ℃,
Three samples had a mean logarithmic value of 6.26 log CFU / g in the range of 10 ⁵ to 10 ⁷ CFU / g.

From the results of these tests, it can be seen that the number of initial bacteria and the number of bacteria after a lapse of time are both high and the hygienic quality is low in the untreated cut vegetables. Comparative Example 2 As cut vegetables, the above Chinese cabbage (divided vertically into four)
Was sterilized only with a sodium hypochlorite solution, and then, in the same manner as in the examples of the present application, about 15 g each was placed in a stomacher bag and sealed, and each at 6 ° C. and 6 ° C.
I saved them one by one. Then, the number of general bacteria of the cut vegetables (3 samples each) stored at each temperature after 3 days and 7 days was examined, and the following results were obtained.

The initial bacterial count of cut vegetables treated with sodium hypochlorite solution was 10 ² to 10 ³ CFU for 3 samples.
The average logarithmic value was 2.75 log CFU / g in the range of / g. When 3 days have passed and 3 samples were stored at 4 ℃,
Average logarithmic value is 2.11 log CFU in the range of 0 ¹ to 10 ³ CFU / g
It was / g. After 3 days and stored at 7 ℃, 3 samples are 1
Average logarithmic value is 2.51 log CFU in the range of 0 ² to 10 ⁴ CFU / g
It was / g. After 7 days, 3 samples will be 1 if stored at 4 ° C.
The average logarithmic value is 2.45 log C in the range of 0 ¹ to 10 ⁴ CFU / g.
It was FU / g. After 7 days and stored at 7 ℃, 3 samples are 1
The average logarithmic value is 2.98 log C in the range of 0 ² to 10 ⁴ CFU / g.
It was FU / g.

Looking at these inspection results, although there was some variation depending on the sample, storage at 4 ° C. and 7 ° C.
Within 7 days of storage, the number of detected bacteria was close to the number of initial bacteria (mean logarithmic value of 2.75 log CFU / g).

Comparing Comparative Example 2 (sterilized with only sodium hypochlorite solution) with that of the present Example, the logarithm of the number of initial bacteria of the Example of the present invention is that of Comparative Example 2. It can be seen that the number of bacteria can be reduced to about 73% in conversion. In addition, when comparing the samples stored at the same temperature and after the same day, the number of bacteria in the example of the present application is 61% (in the case of mutual) and 48% (in the case of mutual) of the numbers of bacteria in Comparative Example 2 respectively. Cases), 58% (for mutual cases), and 70% (for mutual cases).

The cut vegetables treated by the freshness preservation method of the above-mentioned embodiment of the present invention are so-called MA-packable storage bags (for example, trade name of Sumitomo Bakelite Co., Ltd .; P-
Plus), in which case the number of bacteria can be reduced and at the same time the freshness of the sensory surface can be maintained for a long period of time. Therefore, it is possible to provide high-quality cut vegetables in both hygiene and sensory aspects.

Claims (3)

[Claims] 1. The cut vegetables are immersed in a fumaric acid solution in which hydrogen ions are dissociated for primary sterilization, and then the cut vegetables in the fumaric acid solution are taken out and the fumaric acid solution adheres thereto. The cut vegetables as they are are soaked in a sodium hypochlorite solution for secondary sterilization, and then the cut vegetables in the sodium hypochlorite solution are taken out, washed with water and drained, and the drained cut vegetables are stored in a storage bag. A method for maintaining the freshness of cut vegetables, which is characterized in that it is enclosed inside. 2. The concentration of the fumaric acid solution is 1000 to 300.
At 0 ppm, the concentration of the sodium hypochlorite solution is 50-
It is 200 ppm, The freshness maintenance method of the cut vegetable of Claim 1 characterized by the above-mentioned. 3. A storage bag, which is an air-permeable material having a large number of fine pores, has an oxygen concentration of 5 to 10% and a carbon dioxide concentration of 10 to 10 when breathing cut vegetables that are hermetically sealed. The freshness-preserving method for cut vegetables according to claim 1 or 2, wherein a packaging material that is in an equilibrium state at 15% is used.