JP2015198587A - Production method of frozen vegetable and food product including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide production methods of frozen vegetables having excellent texture when being eaten and excellent external appearance, and having a high nutrient residual ratio and long-term preservation, and of food products including the frozen vegetables.SOLUTION: The production method of frozen vegetables includes: a first step of raising the temperature of vegetables until a highest-temperature part reaches 95°C or higher; a second step of dehydrating the vegetables acquired by the first step within 5 minutes until a yield ratio thereof becomes within a range of 70-90%; and a step of freezing the vegetables acquired by the second step.

Description

  The present invention relates to a frozen vegetable having excellent texture and appearance at the time of eating, having a high nutritional survival rate, and having long-term storage stability, and a method for producing a food containing them.

  As a method for producing frozen vegetables, generally, a method in which vegetables are boiled and then frozen is used. However, there is a problem that the texture after thawing is lowered by melting the vegetable pectin by boiling and then damaging and softening the vegetable tissue by freezing. There is also a problem that nutrient components are lost by boiling.

Several methods for preventing softening are known as methods for improving the texture of frozen vegetables.
Patent Document 1 discloses a method of suppressing the growth of ice crystals that cause tissue destruction by immersing vegetables in a solution containing sugar such as trehalose. Patent Document 2 discloses a method for producing antifreeze vegetables by immersing vegetables in ethanol. Both are methods to increase the freezing tolerance of vegetables, but the taste is lowered by adding sweetness due to sugar or the taste of ethanol, and if the sugar or ethanol does not penetrate sufficiently, the effect of improving vegetable hardness Low.

  Patent Document 3 discloses a method for enhancing the cytoplasm by immersing vegetables in an aqueous solution containing calcium salts such as calcium chloride and calcium lactate. However, when the bitterness by a calcium salt is provided, the taste is lowered, and if the calcium salt does not sufficiently penetrate, the effect of improving the hardness of the vegetable is low.

  Patent Document 4 discloses a method for shortening the heating time by immersing vegetables in ethanol before heating to deactivate the enzyme. In this method, since the heating time is short, the texture is maintained before freezing, but when frozen, the texture is destroyed and softened by ice crystals, so that sufficient texture is not maintained in frozen vegetables.

  Further, as a method for improving the texture of frozen vegetables, the following techniques are known in which the vegetables are semi-dried before freezing and the free water in the tissue is reduced to reduce ice crystals.

  Patent Document 5 discloses a method of drying vegetables using osmotic pressure dehydration. However, an unpleasant taste such as salty taste is imparted, and the vegetables are wilted due to tissue damage.

  Patent Document 6 discloses a method of drying vegetables with warm air. However, since vegetables are dehydrated for a long time in an environment at room temperature or higher, enzymatic reactions and ripening progress, and quality and freshness are reduced.

  Patent Documents 7 and 8 disclose a method of reducing enzyme activity and reducing moisture with superheated steam. However, since it is necessary to determine the heating temperature and the heating time according to the strength of the enzyme activity, the history changes and the quality is not stable. In addition, in order to prevent vegetables from being burned by superheated steam, it is heated for a long time at a low temperature, and the dehydration time is prolonged, so that the load on the tissue is large, and as a result, the effect of improving the hardness of the vegetable is reduced. There is a problem.

  Patent Document 9 discloses a method of drying vegetables at a low temperature under reduced pressure. However, there is a problem in that an apparatus for decompressing is required, and it takes time for dehydration, so that productivity is poor, and heat is not applied, so that the enzyme is not deactivated and storage stability is deteriorated.

  Thus, in the prior art, 1) the taste is imparted, 2) the effect of improving the hardness is low, 3) the quality is lowered, and the texture is good and tastes like fresh vegetables. Quality frozen vegetables cannot be produced.

JP-A-6-319501 JP-A-5-252891 Japanese Patent Laid-Open No. 4-190756 JP 2006-204222 A JP 2001-178356 A JP 2005-151939 A International Publication No. 02/080960 JP 2006-271352 A JP 2007-289157 A

  An object of this invention is to provide the manufacturing method of the frozen vegetables which are excellent in the food texture and external appearance at the time of eating, have a high nutrient residual rate, and have long-term preservation | save property, and foodstuffs containing them.

As a result of intensive studies to solve the above problems, the present inventors have as follows: 1) The temperature of vegetables is raised to near the boiling point of water (95 ° C or higher) without uneven heating, and 2) the yield is within a specific range. Dehydrate in a short time until 3) If necessary, deactivate the enzyme without changing the yield, and 4) Freeze the frozen vegetables with excellent texture and appearance and long-term preservation It has been found that it can be manufactured. Moreover, after impregnating a vegetable with ethanol, it finds out that it can manufacture the frozen vegetables which are further excellent in food texture, and do not have an unpleasant taste, and the food containing them by performing the process of said 1) -4), The present invention has been completed.
That is, the present invention relates to the following.
[1] The first step of raising the temperature of the vegetables until the hottest part reaches 95 ° C. or higher, and the yield of the vegetables obtained by the first step within the range of 70 to 90%. A method for producing frozen vegetables, comprising a second step of dehydrating within minutes, and a step of freezing the vegetables obtained by the second step.
[2] The production method according to [1], wherein the temperature difference of the vegetables at the end of the first step is within 30 ° C.
[3] The production method according to [1] or [2], wherein the temperature is increased by heating within 5 minutes after the highest temperature portion of the vegetable exceeds 70 ° C in the first step.
[4] The production method according to any one of [1] to [3], wherein the temperature is increased at an average rate of 6.0 ° C./s or less by heating in the first step.
[5] The production method according to any one of [1] to [4], wherein the temperature is raised by microwave heating or steam heating in the first step.
[6] The production method according to any one of [1] to [5], wherein dehydration is performed at an average rate of 0.05% / s or more by heating in the second step.
[7] The production method according to any one of [1] to [6], wherein dehydration is performed by microwave heating or heating with superheated steam in the second step.
[8] A third step of inactivating the vegetable enzyme between the second step and the freezing step so that the yield of the vegetable obtained in the second step is 5% or less. The production method according to any one of [1] to [7], further comprising a step.
[9] The production method according to [8], wherein the enzyme is deactivated by heating in the third step.
[10] The production method according to [8] or [9], wherein the enzyme is inactivated by steaming and heating in the third step.
[11] The production method according to any one of [8] to [10], wherein the enzyme activity is inactivated to a peroxidase activity of 500 U / vegetable weight of 100 g or less.
[12] The production method according to any one of [1] to [11], further including a step of impregnating vegetables with ethanol before the first step.
[13] A food containing frozen vegetables produced by the production method according to any one of [1] to [12].

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the frozen vegetables which are excellent in the texture and external appearance at the time of eating, have a high nutrient residual rate, and have long-term storage stability, and foodstuffs containing them can be provided.

FIG. 1 shows the relationship between the rate of temperature rise and the stress and the relationship between the rate of dehydration and the stress when the cabbage is heated and dehydrated under each condition and then frozen and thawed. FIG. 2 shows the stress values when the cabbage is untreated, treated with ethanol or calcium chloride, and then frozen and thawed. FIG. 3 shows a photograph taken with an electron microscope when the boiled cabbage and the rapidly heated dehydrated cabbage are frozen and thawed. FIG. 4 shows stress values when various vegetables are frozen and thawed after being boiled or rapidly heated and dehydrated. FIG. 5 shows the residual rate of vitamin C when various vegetables boiled and various vegetables rapidly dehydrated are frozen and thawed. FIG. 6 shows the stress values after heating and after freezing and thawing when the cabbage was treated under various conditions. FIG. 7 shows stress values when the cabbage is frozen and thawed after being treated with various softening prevention techniques. FIG. 8 shows the storage elastic modulus when the cabbage is frozen and thawed after being treated with various softening prevention techniques. FIG. 9 shows the residual ratio of vitamin C when cabbage is treated with various softening prevention techniques and then frozen and thawed. FIG. 10 shows a photograph of the appearance after thawing of frozen Chinese koji made using vegetables processed by combining rapid heating dehydration and ethanol treatment or boiled vegetables.

  Embodiments of the present invention will be described below.

  In the present invention, frozen vegetables refer to vegetables that have been frozen so that they can be eaten as they are or after cooking after being thawed by heating or the like.

  The vegetables used as the raw material of the frozen vegetables of the present invention are not particularly limited, but for example, leaf vegetables such as cabbage, Chinese cabbage, chingensai, spinach, komatsuna; stem vegetables such as onion, leek, asparagus; Fruit vegetables such as bell pepper, cucumber, eggplant, pumpkin; root vegetables such as carrot, radish, turnip, lotus root; flower vegetables such as broccoli, cauliflower; mushrooms such as shiitake mushroom, enoki mushroom, shimeji mushroom, and the like.

  In the method for producing frozen vegetables of the present invention, the yield of the first step in which the temperature of the vegetable is raised until the highest temperature reaches 95 ° C. or higher, and the yield of the vegetable obtained in the first step is 70 to 90%. It is characterized by including the 2nd process of spin-drying | dehydrating in a short time until it becomes, and the process of freezing the vegetable obtained by the 2nd process.

The first step is a step of raising the temperature of the vegetable until it reaches 95 ° C. or more immediately before the start of dehydration so that there is little uneven heating, that is, the product temperature difference of the vegetable is within 30 ° C.
In the present specification, “vegetable product temperature difference” means a temperature difference between the highest temperature portion and the lowest temperature portion between the heated vegetables (hereinafter referred to as “vegetable product temperature difference”). Is sometimes referred to as “uneven heating”.) In the present invention, the temperature difference of the vegetables at the end of the first step is within 30 ° C., preferably within 25 ° C.
The rate of temperature increase in the first step is an average of 6.0 ° C./s or less, preferably an average of 3.0 ° C./s or less, more preferably an average of 2.0 ° C./s or less, and even more preferably an average of 1.0 ° C./s or less. In general, there is less uneven heating when the rate of temperature rise is slower. However, even when the temperature is raised rapidly, the heating unevenness can be reduced by adjusting the temperature at a constant temperature after the temperature rise or by using a heating device such as a continuous microwave heater that raises the food temperature evenly. be able to. Further, the heating means in the first step is not particularly limited, but means having a small yield change rate is preferable in order to shorten the time for dehydration in the next second step. Examples of the heating means in the first step include microwave heating or steam heating. In addition, when performing microwave heating, it is preferable to carry out by low output (for example, 100-200W).
From the viewpoint of improving the quality of the heating time in the first step, the temperature zone and the time zone in which the enzyme reaction proceeds are shortened as much as possible to suppress off-flavor odor, and the tissue is prevented from being damaged and softened by heating. Preferably, it is within 5 minutes after the hottest part of the vegetable exceeds 70 ° C.

The second step is a step of dehydrating the vegetables obtained in the first step in a short time (preferably within 5 minutes) until the yield falls within the range of 70 to 90%.
In this specification, “yield” means the percentage of the weight after dehydration when the weight of vegetables before dehydration is 100%. In the present invention, dehydration is performed in the second step until the yield falls within the range of 70 to 90%.
Examples of the dehydrating means in the second step include dehydration by heating.
When dehydrating by heating in the second step, the dehydration rate is 0.05% / s or more, preferably 0.1% / s or more, more preferably 0.3% / s or more. Moreover, the heating means for dehydrating in the second step is not particularly limited, and examples thereof include microwave heating and heating with superheated steam. In addition, when performing microwave heating, it is preferable to carry out at high output (for example, 700 W or more), and when performing superheated steam heating, it is preferable to carry out at high temperature (for example, 200-250 degreeC).
The heating time in the case of heating and dehydrating in the second step is preferably within 5 minutes from the viewpoint of improving quality such as suppressing the tissue from being damaged and softened by heating.

  For the vegetable freezing step, for example, devices known to those skilled in the art such as IQF (Individual Quick Frozen), air blast, and block freezing devices can be used. The temperature set when freezing vegetables varies depending on the type and quality of the vegetables, but is usually -18 ° C or lower. From the viewpoint of the freezing rate, it is preferable to carry out at a lower temperature so that cracks do not occur. The freezing of vegetables varies depending on the kind and amount of vegetables used, but the center temperature should usually be −5 ° C. or lower within 30 minutes.

  The method for producing frozen vegetables of the present invention inactivates the vegetable enzyme obtained in the second step so that the yield change rate is within 5% between the second step and the freezing step. A third step may be further included.

In the third step, when a vegetable having a relatively high enzyme activity (for example, cabbage, Chinese cabbage) or the like is used, the yield is increased if the vegetable enzyme is not sufficiently deactivated even after the second step. This is a process of inactivating the enzyme with almost no change (yield change rate is within 5%).
Examples of the “enzyme” in the present specification include peroxidase.
Since dehydration is completed in the second step, it is preferable that the yield is hardly changed in the third step. The yield change rate in the third step is preferably within 5%, more preferably within 2%.
Examples of means for inactivating the enzyme in the third step include enzyme inactivation by heating.
The heating conditions for inactivating the enzyme by heating in the third step are conditions that hardly change the yield, that is, the yield change rate is within 5% (preferably within 2%), and the enzyme is lost. The temperature is not particularly limited as long as it is easy to activate (for example, 90 ° C. or higher). Moreover, as a heating means, steaming heating etc. are mentioned, for example.
The enzyme activity is preferably inactivated to 500 U / vegetable weight of 100 g or less as peroxidase activity per 100 g of vegetable, the quality of which is acceptable even after the vegetable is stored for 1 year in a frozen state. Here, peroxidase activity 1U is the amount of enzyme that reacts with 1 μmol of hydrogen peroxide per minute under the conditions of pH 8.0 and 37 ° C.

  The method for producing a frozen vegetable of the present invention may further include a step of impregnating the vegetable with ethanol before performing the first step in order to obtain a texture improving effect.

The step of impregnating the vegetable with ethanol uses a 3% or higher ethanol aqueous solution (preferably a 3 to 60% ethanol aqueous solution, more preferably a 10 to 45% ethanol aqueous solution), and the ethanol concentration in the vegetable is 0.2 to Add ethanol to the vegetable so that it is within the range of 8.7%.
Although it does not specifically limit as a method to make a vegetable impregnate ethanol, For example, immersion, spraying, etc. are mentioned. In particular, immersion is preferable from the viewpoint that the ethanol concentration in vegetables can be managed with high accuracy by setting the concentration and time of the aqueous ethanol solution.
After the vegetable is impregnated with ethanol, the impregnated ethanol is removed until the ethanol concentration in the vegetable is 1% or less by heating in the first step, the second step, and if necessary, the third step. By doing so, it is possible to produce high-quality frozen vegetables free from off-flavors. In addition, when the ethanol concentration in vegetables cannot be reduced to 1% or less by the above heating, it is preferable to add a removal step that does not involve heating such as water exposure and reduced pressure after performing the step of impregnating with ethanol.

  According to the method for producing frozen vegetables of the present invention, since there is no contact with water during heating, water-soluble nutrient components contained in the vegetables do not flow out and are retained in the vegetables. Moreover, according to the manufacturing method of the frozen vegetables of this invention, since the enzyme of vegetables deactivates, it is excellent in long-term preservability.

The “food containing frozen vegetables” in the present specification is not particularly limited as long as it is a food containing frozen vegetables produced by the production method of the present invention. For example, the frozen food produced by the production method of the present invention is used. Examples thereof include mixed vegetables mixed with vegetables, frozen vegetables manufactured by the manufacturing method of the present invention, frozen foods such as Chinese koji mixed with seafood and sauce.
The “food containing frozen vegetables” in the present specification can be produced by a known production method using the same raw materials as known foods, except that the frozen vegetables produced by the production method of the present invention are used. .

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example.

Example 1 Examination of heating unevenness and dehydration rate at temperature rise After heating a cabbage cut to a size of 40 × 30 mm using a home-use microwave oven, it was dehydrated to a yield of 85%. At this time, nine types of specimens having different heating rates and dehydration rates were prepared by changing the W number during heating and dehydration to 200, 500, and 1000 W. As a control, a sample that was boiled at 98 ° C. for 2 minutes was also prepared using a general frozen vegetable manufacturing method as a model. After freezing these specimens, they were naturally thawed and subjected to physical property (stress) measurement and sensory evaluation.
The heating unevenness at the time of temperature increase was measured using a thermography (CPA-E, manufactured by Chino Co., Ltd.). After heating under each condition, the temperature distribution was visualized by thermography, and the difference between the maximum temperature and the minimum temperature was regarded as uneven heating.
For the stress measurement, a texture analyzer (Stable Micro Systems, TA-XT plus) was used. The cabbage was cut into a width of 20 mm in a direction perpendicular to the fibers, and five sheets were stacked and fixed with clips. At this time, extremely thick veins were avoided. This was broken by a wedge plunger with a width of 70 mm and a thickness of 3 mm with a wedge plunger at a rate of 0.3 mm / s and strain of 100%, and the maximum stress obtained was taken as the measured value.
As a method for sensory evaluation, the standard (one point) was a sample that had been boiled at 98 ° C for 2 minutes, modeled on a general frozen vegetable manufacturing method, and the cabbage obtained in each test was incremented by 0.5. Evaluation was made on a scale of points (similar to the standard), 2 points (slightly good), 3 points (good), 4 points (further good), and 5 points (very good). Here, the quality of the texture was evaluated based on a comprehensive sense including other factors such as cabbage hardness and tension. The results are shown in Table 1. Further, FIG. 1 shows the relationship between the heating rate and the stress and the relationship between the dehydration rate and the stress.
In addition, the “crispy feeling” or “crispy” used in the sensory evaluation (texture) in the table below means a sense of firmness and tightness when a vegetable is put in the mouth and chewed. To do.

  The higher the rate of temperature increase, the greater the unevenness of heating when the temperature is increased to just before dehydration. When the dehydration rate was fixed and compared, the texture was better when the heating unevenness was smaller. On the other hand, the faster the dehydration rate, the shorter the processing time becomes possible. When compared at a fixed rate of temperature increase, the shorter the dehydration time, the better the texture.

Example 2 Examination of heating unevenness at the time of temperature rise by steam heating The temperature of cabbage (40 × 30 mm) was raised using a steamer. At this time, six types of specimens having different heating unevenness after the temperature increase were prepared by changing the temperature of the steamer. These specimens were dehydrated to a yield of 85% in 100 seconds using a home microwave oven. The obtained specimen was frozen and then thawed naturally to perform stress measurement and sensory evaluation.
The heating unevenness at the time of temperature increase in the steaming heating was evaluated by directly measuring the temperature using a data logger (GL450, GL450). A thermocouple was inserted into the cabbage, put into a steamer of each condition, and the temperature change was recorded using a data logger, and the difference from the lowest temperature when the highest temperature reached before the start of dehydration was regarded as uneven heating. Stress measurement and sensory evaluation were performed in the same manner as in Example 1. The results are shown in Table 2.

Even when the temperature was raised using steaming heating, the texture was better as the heating unevenness was smaller.
From the results of Examples 1 and 2, the heating unevenness (vegetable product temperature difference) exceeds 30 ° C. Even if the dehydration rate is increased, the food texture does not become good, so the heating unevenness (vegetable product temperature difference) is within 30 ° C. Was confirmed to be preferable.

Example 3 Examination of heating means for temperature rise After heating the cabbage cut into a size of 40 × 30 mm using a household microwave oven or continuous microwave heater, the yield is increased in 45 seconds using the same heating device. Dehydrated to 85%. The obtained specimen was frozen and then naturally thawed for sensory evaluation. The sensory evaluation was performed in the same manner as in Example 1. The results are shown in Table 3.

  Although the heating rate when using a continuous microwave heater was about 3 times the heating rate when using a household microwave oven, the texture was good in all cases. When compared at the same heating rate, the microwave oven diffuses the microwaves and heats the food because of the principle of heating the food, but the continuous microwave heater is the principle that microwaves are directly irradiated to the food Therefore, the heating unevenness is reduced. It has been confirmed that when a heating device such as a continuous microwave heater that raises the temperature of food uniformly is used, a good texture can be obtained even if the heating rate is high.

Example 4 Examination of Time for Temperature Raising A cabbage cut into a size of 40 × 30 mm using a household microwave oven was heated at 200 W, and then dehydrated to a yield of 85% at 1000 W. At this time, six types of specimens with different speeds were prepared by changing the amount of cabbage input. The obtained specimen was frozen and then naturally thawed for sensory evaluation. The sensory evaluation was performed in the same manner as in Example 1. However, evaluation was performed about texture and taste flavor. The results are shown in Table 4.

  The texture improvement effect was acquired under any conditions. However, a nasty odor was generated in the sample whose temperature rise time exceeded 5 minutes. In order to shorten the temperature zone and time zone in which the enzyme reaction proceeds as short as possible, it was confirmed that the temperature raising time is preferably within 5 minutes. Moreover, it is known that softening of vegetables will progress if the temperature of vegetables exceeds about 70 degreeC (Journal of Japanese Cooking Science 30 (1), 62-70, 1997). From the viewpoint of maintaining a good food texture, it was confirmed that the temperature increase is preferably completed within 5 minutes after the highest temperature portion of the vegetable exceeds 70 ° C.

Example 5 Examination of Dehydration Rate Cabbage (40 × 30 mm) was heated by steaming and dehydrated to a yield of 85% at 4 different dehydration rates using a household microwave oven. The obtained specimen was frozen and then thawed naturally to perform stress measurement and sensory evaluation. Stress measurement and sensory evaluation were performed in the same manner as in Example 1. The results are shown in Table 5.

The faster the dehydration rate, the better the texture. On the other hand, when the dehydration time exceeded 6 minutes, the texture was not very good and the quality improvement effect was low.
From the above results, it was confirmed that dehydration is preferably completed within 5 minutes.

Example 6 Examination of enzyme deactivation conditions Cabbage (40 × 30 mm) was heated with first heating (heating unevenness 22.6 ° C.) using a microwave oven at home, and then second heating (dehydration time 50 seconds) And dehydrated to 85% yield. Thereafter, the specimen was steamed (90 seconds) or boiled (60 seconds) to inactivate the enzyme. The obtained specimen was frozen and then thawed naturally to perform stress measurement and sensory evaluation. Stress measurement and sensory evaluation were performed in the same manner as in Example 1.
Peroxidase (POD) activity was measured by the following method. The sample and 33.3 mM Tris-HCl buffer (pH 8.0) were mixed at a weight ratio of 1: 3, crushed with an osterizer, and centrifuged at 14000 rpm for 5 minutes, and the supernatant was used as an enzyme solution. 150 μl of enzyme solution, 150 μl of 66 mM guaiacol, 2000 μl of 33.3 mM Tris-HCl buffer (pH 8.0) were mixed and pre-incubated at 37 ° C. for 5 minutes. To this was added 150 μl of 3.3 mM hydrogen peroxide, and the absorbance increase at 470 nm for 1 minute was measured. The POD activity was calculated using a calibration curve created based on the relationship between the hydrogen peroxide concentration and the absorbance at 470 nm. The amount of enzyme that reacts with 1 μmol of hydrogen peroxide per minute under the conditions of pH 8.0 and 37 ° C. was 1 U. The results are shown in Table 6.

In steaming heating, the enzyme was inactivated while maintaining the best yield, and a good texture could be maintained. On the other hand, in boil heating, water absorption occurred after dehydration, the specimen softened, and the food texture did not become good.
In addition, using cabbage, carrots, and onions, the degree of increase in yield due to boil heating after dehydration was confirmed. The range was 2.6 to 8.3%, and the lower the increase in yield, the better the texture.

Example 7 Examination of ethanol treatment (1) Comparative examination of stress values of ethanol treatment and calcium chloride treatment Samples of cabbage (40 x 30 mm) immersed in 15% ethanol aqueous solution or 5% calcium chloride aqueous solution for 10 minutes, and no control The treated specimens were steamed for 3 minutes, heated and then frozen. This was naturally thawed and the stress was measured. The stress measurement was performed in the same manner as in Example 1. The results are shown in FIG.
The specimen in which vegetable was impregnated with ethanol showed the same maximum stress improvement as the specimen in which calcium chloride was impregnated.

(2) Examination of ethanol concentration in vegetables After cabbage (30 × 40 mm) was immersed in ethanol for 0 to 3 hours, the ethanol concentration in the specimen was measured. Nine types of specimens having different ethanol concentrations in the specimen were prepared. After that, ethanol was removed by freezing with water and steaming at 98 ° C. for 3 minutes to freeze, and the quality after natural thawing was evaluated by stress measurement and sensory evaluation. Physical property (stress) measurement and sensory evaluation were performed in the same manner as in Example 1. However, the standard (1 point) was a frozen product that had not been treated with ethanol and steamed for 3 minutes.
The ethanol concentration was measured by the following method. 50 ml of water was added to 6 to 7 g of the sample and distilled. The volume of the distillate was adjusted to 25 ml, and then measured with a gas chromatograph (manufactured by Shimadzu Corporation, GC-2014) (detector: FID, column: Gaskuropack55, 80-100 mesh, 3.2 mm × 3.1 m (manufactured by GL Sciences Inc.) ), Inlet and detector temperature: 250 ° C., column temperature: 130 ° C., carrier gas: nitrogen 25.0 ml / min, gas pressure: hydrogen 60 kPa, air 50 kPa, injection amount: 2 μl). The results are shown in Table 7.

  It was confirmed that a good texture was obtained by impregnating vegetables with 0.7% or more ethanol. Moreover, food texture improved, so that ethanol concentration became high.

  After cabbage (30 x 40 mm) was steamed at 98 ° C for 3 minutes and heated, 15% ethanol was added to prepare 7 types of samples with different ethanol concentrations. This was sensoryly evaluated. The sensory evaluation was performed in the same manner as in Example 1. However, the evaluation was performed for taste and flavor, and the standard (5 points) was an ethanol concentration 0% product. The results are shown in Table 8.

  It was confirmed that there was almost no influence on the taste by setting the ethanol concentration to 1% or less.

(3) Examination of concentration of ethanol aqueous solution used for immersion Cabbage (30 × 40 mm) was immersed in various concentrations of aqueous ethanol solution to adjust the ethanol concentration in the specimen to 0.7%. Thereafter, ethanol was removed by freezing and steaming at 98 ° C. for 3 minutes, and the quality after natural thawing was evaluated by stress measurement and sensory evaluation. The stress measurement was performed in the same manner as in Example 1. Sensory evaluation and ethanol concentration measurement were performed in the same manner as in Example 7, (2). The results are shown in Table 9.

  A clear texture-enhancing effect was confirmed by using an aqueous ethanol solution having a concentration of 3% or more. Moreover, the texture improvement effect was higher when using high-concentration ethanol.

(4) Examination of heating method for removing ethanol After 100 g of cabbage (40 × 30 mm) was immersed in a 15% aqueous ethanol solution for 10 minutes, ethanol was removed by heating by various methods. The boil was heated at 98 ° C for 120 seconds, the steaming at 98 ° C for 180 seconds, the fried food at 240 ° C for 120 seconds, the frying at 180 ° C for 5 seconds, and the microwave at 500W for 160 seconds. The specimen heated by the above method was frozen, and the quality after natural thawing was evaluated by sensory evaluation. Sensory evaluation and ethanol concentration measurement were performed in the same manner as in Example 7, (2). The results are shown in Table 10.

  In any heating method, the texture improvement effect and the removal of alcohol were confirmed. However, the method (steamed, fried, microwave) in which the heat medium does not directly contact the specimen had a higher texture improvement effect.

Example 8 Observation of cabbage subjected to boiling heating or rapid heating dehydration with an electron microscope 1) A specimen heated by boiling for 2 minutes at 98 ° C. and 2) 500 W ( Specimens dehydrated to a yield of 85% at 500W (dehydration rate 0.3% / s) after heating at a rate of temperature increase of 1.7 ° C / s (hereinafter referred to as "rapid heating dehydration") FIG. 3 shows a photograph that was naturally thawed after freezing and observed with an electron microscope.
In the specimen that had been boiled, the cells were destroyed and many large holes were seen, whereas in the specimen that had been heated and dehydrated, there was almost no damage to the cells.

Example 9 Comparative study of boiling or rapid heating and dehydration using various vegetables Onion (30 x 20 mm), carrot (20 x 50 x 2 mm), pepper (30 x 20 mm), Chinese cabbage (40 x 40 mm) and Chinggensai (40 × 40mm) was 1) boiled at 98 ° C for 2 minutes, or 2) heated at 500W using a home microwave oven, dehydrated to 500% yield and 85% yield, and then frozen. This was naturally thawed and the stress was measured. The stress measurement was performed in the same manner as in Example 1. However, the specimens were measured with one piece without overlapping. The results are shown in FIG.
In any of the vegetables, the stress of the specimen subjected to rapid heating and dehydration was improved as compared with the specimen subjected to boiling heating.

Example 10 Measurement of Vitamin C Residual Ratio Vitamin C content of cabbage prepared in Example 8 and onion prepared in Example 9 was measured. Vitamin C was measured by the following method. Weigh 5 g of frozen vegetables, add 15 ml of 5% metaphosphoric acid and sea sand and crush them, centrifuge (10000 rpm, 5 minutes), collect the supernatant, and collect Rqflex plus 10 (Merck) And quantified. The survival rate was determined with the vitamin C content of fresh vegetables before heating as 100%. The results are shown in FIG.
The cabbage that had been boiled heated had a residual rate of about 58%, whereas the cabbage that had been rapidly heated and dehydrated showed a high residual rate of over 75%. In addition, the remaining rate was about 65% in the onion that was boiled, whereas the onion that was rapidly heated and dehydrated showed a very high rate exceeding 95%.

Example 11 Examination of Combination of Rapid Heat Dehydration and Ethanol Treatment 100 g of cabbage (40 × 30 mm) was 1) untreated (steamed for 3 minutes), 2) ethanol (EtOH) (after dipping in 15% ethanol aqueous solution for 10 minutes, 3) Rapid heating and dehydration (heating for 240 seconds in a household microwave oven for 240 seconds, then heating and dehydrating for 1000 seconds for 1000 seconds), or 4) Rapid heating and dehydration + EtOH (10% immersion in 15% ethanol aqueous solution for 10 minutes) The sample was processed under four conditions of heating in a microwave oven for 200 seconds for 240 seconds and then heating for 1000 seconds at 1000 W for 50 seconds, and the stress was measured. This was snap frozen at −30 ° C. and then naturally thawed, and the stress was measured again. The stress measurement was performed in the same manner as in Example 1. The results are shown in FIG.
In the untreated specimen and the specimen treated only with ethanol, the residual stress rate after heating and after freezing and thawing was around 50%, whereas rapid heating dehydration specimen and rapid heating dehydration specimen combined with ethanol treatment The residual stress rate after heating and after freezing and thawing was as high as around 70%.
Ethanol treatment is a technique that hardens vegetables by denaturing vegetable proteins, and rapid heat dehydration is a technique that reduces ice crystals and reduces damage due to freezing by dehydrating while suppressing tissue damage of vegetables. Higher quality can be achieved by combining technologies with different principles.

Example 12 Comparative examination of texture by various softening prevention techniques The textures of frozen vegetables produced using each technique were compared. 100 g of cabbage (40 × 30 mm) was processed in the steps shown in Table 11 below, and the stress was measured after natural thawing. The stress measurement was performed in the same manner as in Example 1. The results are shown in FIG.

  In the techniques (calcium chloride soaking, osmotic pressure dehydration and heat dehydration) disclosed in the prior literature, the stress is improved, but the quality of the target unfrozen product (fresh vegetables) has not been achieved. On the other hand, in the rapid heating and dehydration of the present invention, it was confirmed that the stress was clearly improved as compared with the technique disclosed in the prior art, and the quality close to the target was achieved. Although the stress improvement effect of ethanol treatment is similar to that of known technology, it has become possible to improve the stress to the same level as that of fresh vegetables without combining with rapid heating dehydration to reduce the quality due to the addition of a different taste. .

Moreover, the effect of vegetable tension by each technique was evaluated as quality other than hardness. Since the vegetables with tension are elastic, the elasticity was measured using a dynamic viscoelasticity measuring device (manufactured by Taisei Corporation, PZ-RHEO). The cabbage after natural thawing was brought into contact with a 10 mm plunger so that extremely thick veins did not enter, and measurement was performed at an amplitude of 10 μm and a frequency of 3 Hz. The obtained storage elastic modulus E ′ was used as a measurement value. The results are shown in FIG.
In the technique disclosed in the prior art, the fiber is strong but has no elasticity and no tension. On the other hand, the rapid heating and dehydration of the present invention improved the elasticity in addition to the stress, and obtained not only the hardness but also the effect of improving the tension of fresh vegetables. Moreover, it became possible to further improve the tension by combining ethanol treatment with rapid heating dehydration.

  Furthermore, the sensory evaluation of the specimen obtained by each technique was performed. The sensory evaluation was performed in the same manner as in Example 1. However, the unfrozen product that is the target quality was set as the standard (5 points), and the quality exceeding the standard was set as 6 points, and the texture (hardness and tension), taste and appearance in each technology were set as evaluation items. The results are shown in Table 12.

  It was confirmed that by using the rapid heating dehydration (and the combination with ethanol treatment) of the present invention, texture (hardness and tension), taste and appearance can be improved and a quality close to the target can be achieved.

Next, the vitamin C content of the specimen obtained by rapid heating dehydration and a combination of rapid heating dehydration and ethanol treatment was measured. The measurement was performed in the same manner as in Example 10. The results are shown in FIG.
It was confirmed that a high residual rate could be maintained even when combined with rapid heating dehydration and ethanol treatment.

Example 13 Preparation of Chinese koji Chinese koji was prepared using vegetables processed by combining rapid heating dehydration and ethanol treatment or boiled vegetables. Specifically, cabbage and Chinese cabbage cut to 30 x 40 mm, with the same amount of sprouts, 300 g of vegetables, 1) 1.5 kW for 80 seconds using a continuous microwave heater Heated, dehydrated to 85% yield, heated for 90 seconds with a steamer, or 2) boiled for 2 minutes at 98 ° C, allowed to cool to below 30 ° C, and this was used for ingredients such as shrimp and Frozen after mixing with sauce. FIG. 10 shows an appearance photograph of the cooked Chinese rice bowl after thawing.
The Chinese bowl using boiled vegetables had a crushed appearance because the vegetables were softened. On the other hand, Chinese koji using vegetables that had been subjected to rapid heating and dehydration had a three-dimensional effect because the tension of the vegetables was maintained, and the appearance quality was improved.

  ADVANTAGE OF THE INVENTION This invention can provide the manufacturing method of the frozen vegetables which are excellent in the texture and external appearance at the time of eating, have a high nutrient residual rate, and have long-term preservation | save, and foodstuffs containing them.

Claims (13)

  The first step of heating the vegetables until the hottest part reaches 95 ° C. or higher, and the vegetables obtained by the first step within 5 minutes until the yield falls within the range of 70 to 90% A method for producing frozen vegetables, comprising a second step of dehydration and a step of freezing the vegetables obtained by the second step.   The manufacturing method of Claim 1 whose product temperature difference of the vegetables at the time of completion | finish of a 1st process is less than 30 degreeC.   The manufacturing method of Claim 1 or 2 which heats within 5 minutes after the part which is the hottest part of vegetables exceeds 70 degreeC in a 1st process.   The manufacturing method according to any one of claims 1 to 3, wherein the temperature is raised at an average rate of 6.0 ° C / s or less by heating in the first step.   The manufacturing method according to any one of claims 1 to 4, wherein the temperature is raised by microwave heating or steaming heating in the first step.   The production method according to any one of claims 1 to 5, wherein dehydration is carried out by heating at an average rate of 0.05% / s or more in the second step.   The manufacturing method of any one of Claims 1-6 which spin-dry | dehydrates by a microwave heating or the heating by superheated steam in a 2nd process.   Between the second step and the freezing step, the third step of inactivating the vegetable enzyme obtained in the second step so that the yield change rate is within 5% The manufacturing method of any one of Claims 1-7 containing.   The production method according to claim 8, wherein the enzyme is deactivated by heating in the third step.   The production method according to claim 8 or 9, wherein the enzyme is deactivated by steaming and heating in the third step.   The production method according to any one of claims 8 to 10, wherein the enzyme activity is deactivated to a peroxidase activity of 500 U or a vegetable weight of 100 g or less.   The manufacturing method according to any one of claims 1 to 11, further comprising a step of impregnating the vegetable with ethanol before the first step.   The foodstuff containing the frozen vegetable manufactured with the manufacturing method of any one of Claims 1-12.