Production metho of frozen vegetables heat-sterilized prior to freezing and ingested unheated after thawing

Abstract

To address such a problem that in medical food service (meals for hospitalized patients and residents of medical facilities, nursing and welfare facilities, etc.), particularly, hospital food service can provide only steamed vegetable salads, and it is not possible to eat raw vegetable salads, in addition, in conventional frozen vegetables, enzymes are deactivated by blanching, which results in poor texture and poor taste.SOLUTION: A production method of frozen vegetables includes: washing harvested vegetables; cutting the washed vegetables; when sterilizing them by heat, subjecting the cut vegetables to pasteurization satisfying conditions for killing coliform bacteria and not aiming at deactivation of enzymes; cooling the pasteurized vegetables; and freezing the cooled vegetables. Accordingly, after thawing, the frozen vegetables can be taken without heating, so as to achieve taste and texture close to those of fresh vegetables.

Description

Technical Field

[0001] The present invention relates to frozen vegetables that are heat-sterilized before freezing and consumed without heating after thawing, as well as methods for producing them.

Background Art

[0002] Conventional frozen vegetables are those in which, after cutting the vegetables, blanching is carried out for the purpose of inactivating the enzymes in the vegetables, and at the same time, achieving the killing of Escherichia coli or the killing of coliforms or the killing of both Escherichia coli and coliforms, followed by cooling and freezing. Blanching is mainly a processing method of heating vegetables, fruits, etc. for a short time and then cooling them. It is often carried out as a pretreatment for frozen vegetables. Most frozen vegetables are soaked in boiling water or exposed to steam before rapid freezing and are heated to 70 - 80% of the cooking heat. The main purpose of blanching is to inactivate the enzymes that cause changes in color, texture, and aroma. Examples of enzymes that cause quality deterioration in vegetables and fruits include lipoxygenase, polyphenol oxidase, polygalacturonase, chlorophyllase, etc. When verifying the effect of blanching, catalase and peroxidase, which are highly resistant to heat, are often used. There is also the purpose of softening the tissue to prevent tissue damage caused by freezing. There are also effects such as preventing changes in color and aroma, preventing changes in nutrients, removing residual pesticides, etc., and reducing harmful microorganisms. Disadvantages include the loss of water-soluble or heat-sensitive nutrients and the generation of wastewater.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0004]

Patent Document 2

[0005] When frozen vegetables produced by the method described in the section of "Background Art" achieve only enzyme inactivation and Escherichia coli killing conditions by blanching, they must be heated and ingested after thawing. When enzyme inactivation, Escherichia coli, and coliform group killing conditions are achieved, and when only coliform group killing conditions are achieved, they can be ingested without heating after thawing. When the enzyme is inactivated, the texture becomes poor and it is not delicious. Normal sterilization is performed with hot water at around 100 degrees (95 to 100 °C). When trying to achieve coliform group killing conditions under this condition, the enzyme will be inactivated. Also, since it is directly in contact with hot water, umami components and nutrients will flow out.

[0006] According to the Mass Cooking Manual (Revised on June 16, 2017), When serving vegetables and fruits, heating or disinfection is essential. Therefore, in medical meals (meals for inpatients and residents in medical facilities, nursing and welfare facilities, etc.), especially in hospital meals, only heated vegetable salads can be provided, and for patients who cannot eat raw vegetable salads, cooks are providing warm vegetable salads. Generally, in medical meals, only warm vegetable salads are served, and warm vegetable salads have a poor texture and are not delicious.

Summary of the Invention

[0007] An object of the present invention is to provide, as a medical salad, frozen vegetables that can be stored for a long time compared to fresh cut vegetables, etc., and that can be eaten as they are (without heating) after thawing, have a good taste, a good texture, and are delicious, and are sterilized frozen vegetables.

Means for Solving the Problems

[0008] An object of the present invention is to ingest frozen vegetables without heating after thawing, without making enzyme inactivation the purpose of blanching. By controlling microbial management, heating conditions, and cooling conditions, a non-heated intake product can be produced. Regarding microbial management Standards for frozen foods (from the Ministry of Health, Labour and Welfare website) (1) Non-heated intake frozen foods (among frozen foods, those that are manufactured or processed and then frozen, and are considered not to require heating when served for eating) must have a bacterial count (total viable count) of 100,000 or less per 1 g of sample, and the coliform group must be negative. (2) Frozen foods for intake after heating must have a bacterial count (total viable count) of 3,000,000 or less per 1 g of sample, and Escherichia coli must be negative.

[0009] Conventional methods for manufacturing frozen vegetables involve cutting the vegetables and performing blanching for the purpose of inactivating enzymes. In this case, the inactivation of enzymes, the reduction of Escherichia coli and the coliform group, and rapid freezing are achieved to manufacture the product. In the present invention, the purpose of blanching is divided into two: enzyme inactivation and coliform group killing conditions. The purpose is narrowed down to good palatability, and only the killing of the coliform group is achieved under heating conditions of low temperature and short time. Therefore, even in the frozen state, browning of the vegetables progresses, so the product was commercialized by setting a short shelf life. If the coliform group killing conditions (central temperature 75°C for 1 minute or more) are met, it can be eaten without heating after thawing. Definition of terms Medical salad: Frozen vegetables that can be stored for a long time compared to fresh cut vegetables, etc., but can be eaten as they are (without heating) after thawing, have a good taste, good texture, are delicious, and are sterilized frozen vegetables Heat-resistant and cold-resistant bag: A bag for putting ingredients, which can be used for heat sterilization and freezing. IQF: Refers to INDIVIDUAL QUICK FROZEN. It means rapid individual freezing.

Brief Description of the Drawings

[0010] Experiment ▲1▼ Cut fresh cabbage into pieces (3×3×30 - 50 mm), Fill 200 g into a heat-resistant and cold-resistant bag, Vacuum pack and perform heating on TIFF2025105422000004.tif10100 Install a button thermometer (Rh manager) with a diameter of about 1 cm at the center of the cabbage, and perform measurement. After the central temperature of the cabbage reaches 75°C, Measure the residual enzymes in the cabbage at 1 minute, 2 minutes, 3 minutes, and 4 minutes. In this experiment, since heating is performed at a constant 80°C, the central temperature does not exceed 80°C. For the measurement method of residual enzymes, the "Peroxidase Activity Measurement Method" was used. There are many types of enzymes, but here, the activity of peroxidase, which is resistant to heat, will be measured. First, collect 5 g of the specimen (shredded cabbage) and control the temperature to room temperature. Use a knife to finely chop 5 g of the specimen and put it into a test tube. Add 1 ml of 1% guaiacol dilution, 1 ml of 0.5% hydrogen peroxide dilution, and 5 ml of distilled water to the test tube respectively, and stir. Completely mix the specimen and the reagent in the test tube. Add the reagent. If there is a change to brown after 2 minutes, it is judged that the enzyme remains. If there is no change, it is judged that the enzyme has been inactivated. Result: No inactivation of the enzyme was confirmed at any time. When measurement was carried out until 13 minutes, the enzyme did not inactivate. Experiment ▲2▼ Cut fresh cabbage into pieces (3×3×30 - 50 mm), perform heating on TIFF2025105422000005.tif10116 After putting the cabbage into hot water, Measure the residual enzymes in the cabbage at 1 minute, 2 minutes, 3 minutes, and 4 minutes. The measurement method of residual enzymes is the same as that in Experiment ▲1▼. Result: No inactivation of the enzyme was confirmed at any time.

Example 1

[0011] The shredded cabbages, chingensai, komatsuna, and daikon leaves produced by the present invention are produced by the production method described below. Visually select the harvested cabbages, chingensai, komatsuna, and daikon leaves, wash them, cut them into pieces of 3×20 - 50 mm, wash them again, immerse them in an aqueous sodium hypochlorite solution with a concentration of 100 ppm for 10 minutes for sterilization, then wash them and dehydrate them in a dehydrator for 60 seconds. Fill 500 g of the dehydrated vegetables into heat - and cold - resistant bags and perform vacuum packaging. Sterilize the vacuum - packaged vegetables (at 92°C for 10 minutes), and perform boiling heat sterilization that satisfies the coliform death condition (at 75°C for 1 minute or more) at the central temperature of the vegetables. After heat sterilization, cool them with running water (water temperature 10°C or lower), and the rapidly frozen (at - 30°C) ones are made into frozen shredded cabbages, chingensai, komatsuna, and daikon leaves.

Example 2

[0012] The shredded cabbages, chingensai, komatsuna, and daikon leaves produced by the present invention are produced by the production method described below. Visually select the harvested cabbages, chingensai, komatsuna, and daikon leaves, wash them, cut them into pieces of 3×20 - 50 mm, wash them again, immerse them in an aqueous sodium hypochlorite solution with a concentration of 100 ppm for 10 minutes for sterilization, then wash them and dehydrate them in a dehydrator for 60 seconds. Fill the dehydrated vegetables into heat - and cold - resistant bags compatible with a microwave oven and perform vacuum packaging. Sterilize the vacuum - packaged vegetables (at 92°C for 10 minutes), and perform boiling heat sterilization that satisfies the coliform death condition (at 75°C for 1 minute or more) at the central temperature of the vegetables. After heat sterilization, cool them with running water (water temperature 10°C or lower), and the rapidly frozen (at - 30°C) ones are made into frozen shredded cabbages, chingensai, komatsuna, and daikon leaves. The heat-resistant and cold-resistant microwave-compatible bag heats the filled vegetables by microwave while in a sealed or semi-sealed state. The frozen vegetables heated inside the microwave bag generate steam due to the moisture in the thawed vegetables, and the steam is appropriately leaked at the pressure release mechanism 25 or the above-mentioned vent hole. Through such heating using steam, the thawed vegetables are cooked into warm vegetables. Measurement of Browning of Experimental ▲3▼ Vegetables due to Residual Enzymes Fresh leafy vegetables (Chinese cabbage, cabbage, spinach, lettuce, scallions, onions, Komatsuna, turnip greens, butterbur, Mitsuba, chrysanthemum greens, Mizuna, celery, asparagus, cauliflower, broccoli, leeks, garlic, daikon leaves) and root vegetables (daikon radish, carrots, potatoes, taro, turnips, burdock, lotus root, sweet potato), and fruit vegetables (cucumbers, eggplants, tomatoes, bell peppers, pumpkins, sweet corn, green beans, green peas, soybeans, edamame) were cut, washed, filled into heat-resistant and cold-resistant bags, vacuum-packed, and based on the methods of Experiment ▲1▼ and Experiment ▲2▼, only coliform bacteria were sterilized without inactivating the enzymes, cooled, frozen, and stored at -18°C to measure whether browning due to residual enzymes occurred. For Chingen vegetables, Komatsuna, and daikon leaves, browning due to residual enzymes was observed within two weeks from the measurement, but it was still sellable. From the measurement, after four weeks, the green leaf part became darker, and the color of the white stem part became darker. Since browning was observed in some parts of the leaves, it was considered unsellable. Regarding cabbage, no browning was observed even after six months had passed.

Claims

1. Fresh vegetables that have been harvested, washed, cut, filled into heat-resistant and cold-resistant bags, vacuum-packed, heat-sterilized with water or steam, killing coliform bacteria, without inactivating enzymes, quick-frozen, after thawing, can be ingested without heating, Method for producing frozen vegetables.

2. Fresh vegetables that have been harvested, washed, cut, filled into heat-resistant and cold-resistant bags, filled into a microwave-oven-compatible bag, vacuum-packed, heat-sterilized with water or steam, killing coliform bacteria, without inactivating enzymes, quick-frozen, after thawing, can be ingested without heating, Method for producing frozen vegetables.

3. The method for producing frozen vegetables according to claim 1 or 2, wherein the heat sterilization is carried out at 80 to 94 °C and the treatment is carried out so that the central temperature reaches 75 °C × 1 minute or more, which is the condition for killing coliform bacteria.

4. The method for producing frozen vegetables according to claim 3, wherein the heat sterilization is carried out at 80 to 94 °C and the treatment is carried out so that the central temperature is 80 °C or lower as a condition not aimed at inactivating enzymes.

5. The method for producing frozen vegetables according to claim 4, wherein the change over time of browning due to residual enzymes is used as a criterion for setting the expiration date.

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