JP6959772B2 - How to evaluate the quality of frozen vegetables after thawing - Google Patents

Description

The present invention relates to a method for evaluating quality of frozen vegetables after thawing.

Conventionally, freezing treatment is performed for long-term storage of vegetables. As a method for evaluating the quality of such frozen vegetables after thawing, ice crystal observation (freezing substitution method, near-infrared spectroscopy), which is a method of observing ice crystals during freezing or ice crystal scars after freezing and thawing. Method), observation of an object with a microscope or an electron microscope, etc. are known. On the other hand, as a method other than "observation", measurement of the amount of drip and the like can be mentioned. Patent Document 1 describes that the quality of frozen vegetables after thawing is evaluated by measuring the amount of drip after thawing.

Japanese Unexamined Patent Publication No. 2009-228966

However, it has been difficult to quantify and quantitatively compare the evaluation results by the method of observing ice crystals or observing the subject. In addition, in observations using freeze-replacement method, near-infrared spectroscopy, and electron microscopy, "it takes time to prepare the subject", "it takes skill to prepare and observe the subject", and "dedicated equipment". There was a problem such as "necessary and expensive".

On the other hand, in the method of measuring the amount of drip, there is a large error depending on the type of the subject or the thawing method, and it is difficult to match the measurement result with the sensory evaluation or the observation evaluation.

Therefore, an object of the present invention is to provide a method for evaluating the quality of frozen vegetables after thawing, which can be quantified and can be easily matched with the result of sensory evaluation.

The present inventors have found that the above problems can be solved by using the Young's modulus of the thawed vegetables in the method of evaluating the quality of frozen vegetables after thawing, and have completed the present invention.

That is, the present invention provides the following [1] to [8].
[1] A method for evaluating the quality of frozen vegetables after thawing, which includes a step of calculating the breaking stress and breaking strain of vegetables after thawing, and a step of calculating Young's modulus from the breaking stress and breaking strain. A method comprising a step of evaluating the quality of vegetables after thawing based on Young's modulus.
[2] The method according to [1], further comprising a step of calculating the drip rate based on the drip amount of vegetables after thawing and the weight of frozen vegetables, and evaluation is performed based on Young's modulus and drip rate.
[3] A method for determining a quality evaluation standard value for evaluating the quality of frozen vegetables after thawing, which is a step of calculating the breaking stress and breaking strain of vegetables after thawing, and Young from the breaking stress and breaking strain. A method comprising a step of calculating a rate, a step of performing a sensory evaluation of vegetables after thawing, and a step of determining a first quality evaluation standard value from the young rate and the result of the sensory evaluation.
[4] The first quality evaluation reference value is a) the lower limit of the Young's modulus at which the sensory evaluation is good; and / or b) the upper limit of the Young's modulus at which the sensory evaluation is good; in [3]. The method described.
[5] Further provided with a step of observing and evaluating vegetables after thawing, the first quality evaluation standard value is
The method according to [3], wherein a) a lower limit of Young's modulus that results in good sensory evaluation and observational evaluation; and / or b) an upper limit of Young's modulus that results in good sensory evaluation and observational evaluation.
[6] Further includes a step of calculating the drip rate based on the amount of drip of vegetables after thawing and the weight of frozen vegetables, and a step of determining a second quality evaluation standard value from the drip rate and the result of sensory evaluation. The method according to any one of [3] to [5].
[7] The second quality evaluation reference value is c) the upper limit of the drip rate at which the sensory evaluation is good; and / or d) the lower limit of the drip rate at which the sensory evaluation is good; in [6]. The method described.
[8] A step of observing and evaluating the vegetables after thawing is further provided, and the second quality evaluation reference value is c) the upper limit of the drip rate at which the sensory evaluation and the observation evaluation are good; and / or d. ) The lower limit of the drip rate at which the sensory evaluation and the observation evaluation are good;
The method according to [6].

According to the present invention, it is possible to provide a method for evaluating the quality of frozen vegetables after thawing, which can be quantified and can be easily matched with the result of sensory evaluation.

6 is a photograph showing the results of observing the samples of Examples 3 to 6 with an electron microscope.

Hereinafter, the present invention will be described in detail, but the present invention is not limited to the following embodiments.

The method for evaluating the quality of frozen vegetables after thawing according to an embodiment of the present invention is a step of calculating the breaking stress and breaking strain of vegetables after thawing, and calculating Young's modulus from the breaking stress and breaking strain. A step of evaluating the quality of vegetables after thawing based on Young's modulus is provided.

Vegetables for preparing frozen vegetables include both raw vegetables that are normally eaten raw and those that are cooked and eaten. Vegetables are preferably vegetables other than leaf vegetables, such as potatoes, root vegetables, stem vegetables, phosphorus stem vegetables, and beans. Vegetables other than leafy vegetables are not particularly limited. Hasu, Hishi, Artichoke, Edamame, Sayaendo, Snap peas, Greenpeace, Pumpkin, Kuwai, Gobo, Takenoko, Onion, Tsukushi, Chili, Sweet corn, Nabana, Carrot, Carrot, Stem garlic, Beet, Fukinoto, Fujimame , Broccoli, horse radish, yurine, garlic, garlic, eshalot and wasabi.

In the evaluation of the present embodiment, first, the above-mentioned vegetables are frozen to obtain frozen vegetables. The vegetables may be frozen in the unheated raw vegetables state. If necessary, the raw vegetables may be frozen in a peeled state or in a state of being cut to an appropriate size. The water content of the raw vegetables is preferably 5 to 90% by mass, more preferably 20 to 90% by mass, and even more preferably 50 to 90% by mass.

Vegetables may be heat-treated and then frozen. The heat treatment may be, for example, a treatment in which raw vegetables are brought into contact with superheated steam. The method for bringing raw vegetables into contact with superheated steam is not particularly limited, but for example, a method of spraying superheated steam on vegetables in an open system, an atmosphere of superheated steam in a closed system (a space filled with superheated steam). ), And various other methods such as placing vegetables in) can be mentioned. In addition, vegetables can be brought into contact with superheated steam using a commercially available superheated steam treatment device (Healsio (registered trademark), manufactured by Sharp Corporation) or the like.

The temperature of superheated steam (treatment temperature of superheated steam treatment) may be appropriately adjusted according to the time for contacting the vegetables with the superheated steam (treatment time for superheated steam treatment) or the type of vegetables. The treatment temperature may be 110-200 ° C, 120-200 ° C, 130-180 ° C, or 140-180 ° C. The treatment temperature may be constant or variable while the vegetables are in contact with superheated steam.

The time for contacting vegetables with superheated steam (treatment time for superheated steam treatment) may be appropriately adjusted according to the temperature at which vegetables are brought into contact with superheated steam (treatment temperature for superheated steam treatment) or the type of vegetables. The treatment time may be 1 minute or more, 5 minutes or more, 10 minutes or more, or 20 minutes or more from the viewpoint of sufficiently obtaining the heating effect. The treatment time may be 120 minutes or less, 90 minutes or less, 60 minutes or less, or 40 minutes or less from the viewpoint of suppressing deterioration of texture. The time for contacting the vegetables with the superheated steam is, for example, preferably 6 to 10 minutes when the treatment temperature of the superheated steam is 200 ° C., and preferably 10 to 20 minutes when the treatment temperature of the superheated steam is 170 ° C. When the treatment temperature of superheated steam is 140 ° C., it is preferably 20 to 30 minutes.

The freezing conditions for preparing frozen vegetables may be, for example, rapid freezing at -30 to −35 ° C. for 1 to 24 hours (rapid freezing), or 24 to 168 hours at -3 to -5 ° C. You may freeze it gently under the condition (slow freezing).

The frozen vegetables mentioned above are usually thawed before cooking. The evaluation method in the present embodiment is a method of evaluating the quality of vegetables thawed for cooking. The thawing conditions for thawing frozen vegetables may be, for example, at room temperature, refrigerated conditions at 4 to 10 ° C., or by using a microwave oven. When using a microwave oven, it may be heated at the output (wattage) normally used for cooking. In the present specification, the thawed state means a state in which the core temperature of the vegetables after thawing is 4 ° C. or higher.

In the step of obtaining the breaking stress and breaking strain of the thawed vegetables according to the evaluation method according to the present embodiment, the breaking stress can be obtained by the following formula (1), and is measured by, for example, a leometer. Can be done. In the present specification, the breaking stress may be the average value (average breaking stress) of the measured values in a plurality of samples.
Breaking stress (Pa) = maximum load value (N) / area to which the load is applied (m ² ) ... (1)

The breaking strain can be obtained by the following equation (2), and can be measured by, for example, a rheometer. In the present specification, the breaking strain may be the average value (average breaking strain) of the measured values in a plurality of samples.
Break strain = thickness of break deformation (mm) / thickness of sample (mm) ... (2)

In the measurement of breaking stress or breaking strain, the temperature of the vegetables to be measured after thawing may be room temperature (about 20 to 30 ° C), or at a temperature set assuming the temperature at the time of eating. There may be. For example, when it is assumed that the thawed vegetables are eaten in a refrigerated state, the measurement temperature of breaking stress or breaking strain may be about 1 to 10 ° C, and it is assumed that the vegetables are cooked and eaten. If so, the measurement temperature may be about 30 to 60 ° C., which is the temperature after cooking. The measurement temperature of the breaking stress or breaking strain of the vegetables whose quality is to be compared after thawing is preferably the same temperature among the vegetables whose qualities are to be compared.

In the step of calculating Young's modulus from breaking stress and breaking strain, Young's modulus can be obtained by the following formula (3). In the present specification, Young's modulus may be an average Young's modulus obtained from the average breaking stress and the average breaking strain.
Young's modulus (Pa) = breaking stress / breaking strain ... (3)

In the step of evaluating the quality of vegetables after thawing based on Young's modulus, the method of evaluating that the quality of vegetables after thawing is good is, in one embodiment, using the Young's modulus of a predetermined value as a reference value as a reference value. It can be evaluated based on that value. The reference value of Young's modulus, which can be said to have good quality of vegetables after thawing, can be determined by the method described later.

In another embodiment, the method for evaluating the quality of frozen vegetables after thawing further comprises a step of calculating the drip rate based on the amount of drip of the vegetables after thawing and the weight of the frozen vegetables, and the evaluation includes the Young rate and the evaluation. It may be done based on the drip rate.

The amount of drip means the amount of drip (moisture) generated after thawing frozen vegetables. The drip rate can be calculated by the following formula (4).
Drip rate (%) = drip amount (g) / weight of frozen vegetables (g) x 100 ... (4)

In this case, the quality of the thawed vegetables can be evaluated based on Young's modulus and drip rate. The method for evaluating the quality of the thawed vegetables is, for example, when the above-mentioned Young's modulus is a value equal to or higher than a predetermined value and the drip rate is a value equal to or lower than a predetermined value, the thawed vegetables are evaluated. It can be said that the quality of the vegetables is good. The range of Young's modulus and drip rate, which can be said to be good quality of vegetables after thawing, may vary according to the evaluation criteria determined by the method described later.

The method for determining the quality evaluation reference value for evaluating the quality of frozen vegetables after thawing according to an embodiment of the present invention includes a step of calculating the breaking stress and breaking strain of the vegetables after thawing, and the breaking stress and the breaking strain. It includes a step of calculating the Young rate from the breaking strain, a step of performing a sensory evaluation of the vegetables after thawing, and a step of determining a first quality evaluation standard value from the Young rate and the result of the sensory evaluation. The step of calculating the breaking stress and breaking strain of vegetables after thawing and the step of calculating Young's modulus from the breaking stress and breaking strain are based on the above-mentioned equations (1), (2), and (3). Can be done.

In one embodiment, the first quality evaluation reference value may be determined as a) a lower limit of Young's modulus in which the sensory evaluation is good; and / or b) an upper limit of the Young's modulus in which the sensory evaluation is good. .. In this case, the first quality evaluation reference value can be performed by the following method. First, a sample of thawed vegetables is prepared and sensory evaluation is performed. The sensory evaluation performed in the present embodiment can be performed, for example, by a trained panelist evaluating evaluation items such as hardness and elasticity of the thawed vegetables and giving points. Then, a standard of points that can be said to have a good sensory evaluation is set. The criteria for scoring that the quality of vegetables after thawing is good may be, for example, 5 points or more when evaluated on a 10-point scale.

Next, the Young's modulus is compared with respect to the sample judged to have good quality by the sensory evaluation, and the lower limit value and / or the upper limit value of the Young's modulus of the sample judged to have good sensory evaluation is determined. When only the lower limit of Young's modulus is determined as the first evaluation reference value, the range above the lower limit of Young's modulus can be determined as the range in which the quality of frozen vegetables after thawing is good. When determining the lower and upper limits of Young's modulus as the first evaluation reference value, the range between the lower and upper limits of Young's modulus is determined as the range in which the quality of frozen vegetables after thawing is good. be able to. When the range of Young's modulus determined based on the first quality evaluation standard value is satisfied, it can be said that the quality of frozen vegetables after thawing is good.

In the step of determining the first quality evaluation standard value from the Young's modulus and the result of the sensory evaluation, first, the ratio of the Young's modulus in the vegetables after thawing to the Young's modulus in the vegetables before freezing (Young's modulus in the vegetables after thawing). / Young's modulus of vegetables before freezing × 100) may be calculated as the relative Young's modulus. In this case, after determining the range of the relative Young's modulus in which the quality of the vegetables after thawing can be said to be good, the Young's modulus corresponding to the value of the relative Young's modulus is a sample judged to have a good sensory evaluation. It can be determined as the lower limit value and / or the upper limit value of Young's modulus of. The range of relative young rate, which can be said to be good quality of vegetables after thawing, may vary depending on the type of vegetables before freezing to be evaluated or the state of vegetables before freezing, and raw vegetables are frozen. The range of the relative young rate, which can be said to be good in the quality of the thawed vegetables, may be different between the case where the heat-treated vegetables are frozen and the case where the heat-treated vegetables are frozen. For example, when the vegetables before freezing are raw carrots, the range of the relative Young's modulus in which the quality of the carrots after thawing can be said to be good can be 4 to 99.9% in one embodiment. When the vegetables before freezing are heat-treated carrots, the range of the relative Young's modulus in which the quality of the carrots after thawing can be said to be good can be 5 to 99.9% in one embodiment.

In another embodiment, the method of determining the quality evaluation reference value for evaluating the quality of frozen vegetables after thawing may further include a step of observing and evaluating the vegetables after thawing. In this case, the first quality evaluation reference value is a) the lower limit of Young's modulus in which the sensory evaluation and observation evaluation are good; and / or b) the upper limit of the Young's modulus in which the sensory evaluation and observation evaluation are good; May be decided.

The observational evaluation may be carried out in one embodiment by observing the state of the vegetables before freezing and the vegetables after thawing using a microscope or an electron microscope and visually comparing the states. In the observation evaluation, it can be determined that the quality of frozen vegetables after thawing is good when the state of the observation surface is smooth and the area of the voids is equal to or less than a predetermined area.

In the present embodiment, the Young's modulus of the sample judged to be good in both the sensory evaluation and the observation evaluation may be compared, and the lower limit value and / or the upper limit value of the Young's modulus may be determined, and this lower limit value may be determined. And / or the upper limit value can be used as the first evaluation reference value. By further providing a step of observing and evaluating the vegetables after thawing, it is possible to more accurately determine the quality evaluation reference value for evaluating the quality of the frozen vegetables after thawing.

The method of determining the quality evaluation standard value for evaluating the quality of frozen vegetables after thawing is the process of calculating the drip rate based on the drip amount of the thawed vegetables and the weight of the frozen vegetables, and the drip rate and sensory evaluation. A step of determining a second quality evaluation reference value from the result may be further provided. The step of calculating the drip rate based on the amount of drip of vegetables after thawing and the weight of frozen vegetables before thawing can be performed based on the above-mentioned formula (4).

The second quality evaluation reference value may be determined in one embodiment as c) an upper limit of the drip rate at which the sensory evaluation is good; and / or d) a lower limit of the drip rate at which the sensory evaluation is good; .. In this case, the first quality evaluation reference value can be performed by the following method. First, a plurality of samples of thawed vegetables are prepared and sensory evaluation is performed. The sensory evaluation may be the same method as the step of determining the first quality evaluation reference value described above.

Next, the drip rate is compared with respect to the sample judged to have good quality by the sensory evaluation, and the upper limit value and / or the lower limit value of the drip rate is determined. When only the upper limit of the drip rate is determined, the range below the upper limit of the drip rate can be determined as the range in which the quality of frozen vegetables after thawing is good. When determining the upper limit value and the lower limit value of the drip rate, the range between the upper limit value and the lower limit value of the drip rate can be determined as the range in which the quality of frozen vegetables after thawing is good.

The range of the drip rate may vary depending on the type of vegetables before freezing to be evaluated or the state of vegetables before freezing, and there are cases where raw vegetables are frozen and cases where heat-treated vegetables are frozen. Therefore, the range of the drip rate at which the quality of the vegetables after thawing can be said to be good may be different. For example, when the vegetables before freezing are raw carrots, the range of the drip rate at which the quality of the carrots after thawing can be said to be good can be 0.1 to 9% in one embodiment, and also. When the vegetables before freezing are heat-treated carrots, the range of the relative young rate at which the quality of the thawed carrots can be said to be good can be 0.1 to 8% in one embodiment.

In the present embodiment, the quality evaluation standard value is determined based on the standard values of both the first quality evaluation standard value and the second quality evaluation standard value. That is, when both the Young's modulus range determined based on the first quality evaluation standard value and the drip rate range determined based on the second quality evaluation standard value are satisfied, after thawing of frozen vegetables. It can be said that the quality is good. This makes it possible to more accurately determine the quality evaluation reference value for evaluating the quality of frozen vegetables after thawing.

In the step of determining the second quality evaluation reference value, the first quality evaluation reference value may be determined by comparing the sensory evaluation result and the observation evaluation result of the thawed vegetables. The observation evaluation may be performed by the same method as the step of determining the first quality evaluation reference value described above.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

[Example 1]
145 g (14 to 15 slices) of raw carrots formed into a ginkgo shape having a thickness of 1 cm were rapidly frozen at −35 ° C. for 24 hours to prepare frozen carrots. This frozen carrot was allowed to stand in a refrigerator set at about 4 ° C. for 24 hours to thaw, and used as a sample for evaluation.

[Example 2]
In Example 1, a sample for evaluation was obtained by the same method as in Example 1 except that frozen carrots were prepared by slowly freezing at −5 ° C. for 168 hours.

[Example 3]
In Example 1, a sample for evaluation was obtained by the same method as in Example 1 except that the frozen carrot was thawed at 500 W for about 2 minutes in a microwave oven (ER-K38, manufactured by Toshiba Corporation).

[Example 4]
In Example 2, a sample for evaluation was obtained by the same method as in Example 2 except that the frozen carrot was thawed at 500 W for about 2 minutes in a microwave oven.

[Example 5]
145 g (14 to 15 slices) of raw carrot molded into a ginkgo shape with a thickness of 1 cm is brought into contact with superheated steam at 120 ° C. for 10 minutes using a superheated steam treatment device (Healsio AX-X2, manufactured by Sharp Corporation). rice field. The heated carrots were rapidly frozen for 24 hours to prepare frozen carrots. The frozen carrot was thawed at 500 W for about 2 minutes in a microwave oven to prepare a sample for evaluation.

[Example 6]
In Example 5, a sample for evaluation was obtained by the same method as in Example 5 except that frozen carrots were prepared by slowly freezing at −5 ° C. for 168 hours.

[Comparative Example 1]
In Example 1, unfrozen raw carrots were used as a sample for evaluation.

[Comparative Example 2]
In Example 5, unfrozen and heated carrots were used as a sample for evaluation.

<Calculation of Young's modulus>
For the samples of Examples 1 to 6 and Comparative Examples 1 and 2, the maximum value of the load and the area to which the load was applied were measured using a rheometer (RHEONER II CREEPMETERRE2-3305B, manufactured by Yamaden Co., Ltd.). The breaking stress was calculated based on these values. The measurement was performed 5 times, and the average value of the breaking stress was obtained. Further, with respect to the thawed sample, the thickness of the sample after fracture deformation and the thickness of the sample were measured using the above rheometer, and the fracture strain was calculated based on these values. The measurement was performed 5 times, and the average value of the breaking strain was obtained. Breaking stress In the measurement for obtaining breaking strain, the temperature of the sample to be measured was set to 25 ° C. Next, the Young's modulus of the sample was calculated based on the average value of the breaking stress and the breaking strain. The results are shown in Table 1.

<Sensory evaluation>
The samples of Examples 1 to 6 and Comparative Examples 1 to 2 were subjected to sensory evaluation by five panelists who were found to be suitable in the discrimination test of five tastes (sweet, acid, salt, bitterness, umami). As evaluation items, a comprehensive evaluation based on "hardness" and "elasticity" was requested. As for the evaluation points, the maximum score is 10, and it can be said that the higher the score, the better the quality. Table 1 shows the average value of the evaluation points.

<Observation evaluation>
The state of the samples of Examples 3 to 6 after thawing was observed using an electron microscope (VHX-2000, manufactured by KEYENCE CORPORATION). The results are shown in FIG. In FIG. 1, (a) corresponds to the evaluation result of Example 3, (b) corresponds to the evaluation result of Example 4, (c) corresponds to the evaluation result of Example 5, and (d) corresponds to the evaluation result of Example 6.

<Measurement of drip rate>
For the samples of Examples 1 to 6, the drip generated at the time of thawing was collected, and the weight thereof was measured to obtain the drip amount. Next, the drip rate (%) was determined from the weight and drip amount of the sample before thawing. The results are shown in Table 2.

Claims (8)

It is a method for evaluating the quality of frozen vegetables after thawing.
The process of calculating the breaking stress and breaking strain of vegetables after thawing,
The step of calculating Young's modulus from the breaking stress and the breaking strain, and
A step of evaluating the quality of the vegetables after thawing based on the Young's modulus, and
A method. A step of calculating the drip rate based on the amount of drip of the vegetables after thawing and the weight of the frozen vegetables is further provided.
The method according to claim 1, wherein the evaluation is performed based on the Young's modulus and the drip rate. It is a method of determining the quality evaluation standard value for evaluating the quality of frozen vegetables after thawing.
The process of calculating the breaking stress and breaking strain of vegetables after thawing,
The step of calculating Young's modulus from the breaking stress and the breaking strain, and
The process of performing sensory evaluation of the vegetables after thawing and
A step of determining a first quality evaluation reference value from the Young's modulus and the result of the sensory evaluation, and
A method. The first quality evaluation standard value is
a) Lower limit of Young's modulus that makes the sensory evaluation good; and / or b) Upper limit of Young's modulus that makes the sensory evaluation good;
The method according to claim 3. Further provided with a step of observing and evaluating the vegetables after thawing,
The first quality evaluation standard value is
a) The lower limit of the Young's modulus that makes the sensory evaluation and the observation evaluation good; and / or b) The upper limit of the Young's modulus that makes the sensory evaluation and the observation evaluation good;
The method according to claim 3. A step of calculating the drip rate based on the amount of drip of the vegetables after thawing and the weight of the frozen vegetables, and
The method according to any one of claims 3 to 5, further comprising a step of determining a second quality evaluation reference value from the drip rate and the result of the sensory evaluation. The second quality evaluation standard value is
c) The upper limit of the drip rate that makes the sensory evaluation good; and / or d) The lower limit of the drip rate that makes the sensory evaluation good;
The method according to claim 6. Further provided with a step of observing and evaluating the vegetables after thawing,
The second quality evaluation standard value is
c) The upper limit of the drip rate that makes the sensory evaluation and the observation evaluation good; and / or d) The lower limit of the drip rate that makes the sensory evaluation and the observation evaluation good;
The method according to claim 6.

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