How frozen vegetables are produced

Abstract

To provide a production method of a frozen vegetable which suppresses reduction in texture of the frozen vegetable obtained by freezing a heated vegetable due to freezing and thawing.SOLUTION: A production method of a frozen vegetable comprises the following steps 1 and 2: the step 1 of heating a vegetable in presence of polyglycerol condensed ricinoleic acid ester; and the step 2 of freezing the vegetable heated in the step 1.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing frozen vegetables. [Background technology]

[0002] Conventionally, frozen vegetables used in frozen prepared foods that can be eaten simply by thawing, such as frozen chinjaorusu (fried pork with green peppers) and frozen champon (champon), are previously heated by frying, boiling, etc., before being frozen. Generally, such frozen vegetables have a problem in that the desirable texture after heating is deteriorated during the cold thawing process.

[0003] As techniques for suppressing deterioration in texture due to cold thawing of frozen vegetables, there have been disclosed a method for producing frozen foods and beverages selected from the group consisting of frozen cereals, frozen vegetables, frozen fruits, frozen noodles, frozen rice and frozen pulp drinks, which is characterized by adding 0.2 to 30% (w / w) of α,α-trehalose and then freezing or freeze-drying (Patent Document 1), and a method for producing frozen vegetables, which is characterized by soaking vegetables in a solution containing urea and then freezing (Patent Document 2). However, these technologies have their advantages and disadvantages, and there has been a demand for an excellent method for producing frozen vegetables that can suppress the deterioration of texture caused by cold thawing when frozen vegetables are obtained by freezing cooked vegetables. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-169766 A [Patent Document 2] JP 2001-224304 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention aims to provide a method for producing frozen vegetables, which can suppress deterioration in texture due to cold thawing of frozen vegetables obtained by freezing heated vegetables. [Means for solving the problem]

[0006] As a result of intensive research to solve the above-mentioned problems, the inventors discovered that by heating vegetables in the presence of a specific emulsifier and then freezing them, the deterioration in texture of the resulting frozen vegetables due to cold thawing can be suppressed, and based on this finding, they have developed the manufacturing method of the present invention.

[0007] That is, the present invention provides a method for producing frozen vegetables, comprising the following steps 1 and 2: Step 1: Heating vegetables in the presence of polyglycerol condensed ricinoleic acid ester Step 2: Freezing the vegetables cooked in step 1 It consists of: Effect of the Invention

[0008] The frozen vegetables obtained by the production method of the present invention are inhibited from losing texture due to cold thawing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The vegetables used in the production method of the present invention are not particularly limited, and examples thereof include fruit vegetables, root vegetables, leafy vegetables, stem vegetables, flower vegetables, and sprouted vegetables. Examples of fruit vegetables include eggplant, tomato, bell pepper, red pepper, shishito pepper, cucumber, pumpkin, pea, green bean, broad bean, corn, and okra. Examples of root vegetables include potato, radish, turnip, carrot, sweet potato, burdock, and taro. Examples of leafy vegetables include cabbage, Chinese cabbage, lettuce, chrysanthemum, spinach, green onion, and Chinese chive. Examples of stem vegetables include asparagus, onion, green onion, garlic, and ginger. Examples of flower vegetables include broccoli, cauliflower, and Japanese ginger. Examples of sprouted vegetables include bean sprouts, radish sprouts, and pea sprouts. Among these, germinated vegetables are preferred, and bean sprouts are more preferred, from the viewpoint of ease of exerting the effects of the production method of the present invention.

[0010] The vegetables used in the production method of the present invention may be pretreated, such as by washing, removing unnecessary parts, and chopping into pieces of an appropriate size, before being heated.

[0011] The production method of the present invention is characterized by carrying out the following steps 1 and 2 using the above-mentioned vegetables.

[0012] [Process 1] Step 1 is a step of heating vegetables in the presence of polyglycerol condensed ricinoleic acid ester. The polyglycerol condensed ricinoleic acid ester used in step 1 is an esterification product of polyglycerol and condensed ricinoleic acid, and is produced by a known esterification reaction or the like. The polyglycerol is usually a mixture of polyglycerols with different degrees of polymerization obtained by heating glycerol, glycidol, epichlorohydrin, etc., and subjecting them to a polycondensation reaction. Examples of the polyglycerol include those having an average degree of polymerization of about 2 to 15. Preferably, the average degree of polymerization is about 3 to 10. The condensed ricinoleic acid is a mixture obtained by heating ricinoleic acid and subjecting it to a polycondensation reaction. Examples of the condensed ricinoleic acid include those having an average degree of polymerization of about 2 to 10. Preferably, the average degree of polymerization is about 3 to 6.

[0013] The heating method in step 1 is not particularly limited, and examples thereof include stir-frying, baking, boiling, stewing, steaming, deep-frying, etc. The purpose of heating is not particularly limited, and examples thereof include cooking heating, blanching (heating for the purpose of deactivating enzymes, sterilization, etc.), and cooking heating is preferred.

[0014] In step 1, the method of heating in the presence of a polyglycerol condensed ricinoleate is not particularly limited as long as the polyglycerol condensed ricinoleate is in contact with the vegetables during heating, and examples of such methods include stir-frying vegetables using fats and oils in which a polyglycerol condensed ricinoleate is dispersed as a frying oil when stir-frying. For example, examples of such methods include baking vegetables by uniformly mixing fats and oils in which a polyglycerol condensed ricinoleate is dispersed with the vegetables and baking the vegetables in an oven or the like. For example, examples of such methods include boiling vegetables by boiling vegetables using water mixed with a polyglycerol condensed ricinoleate as the boiling water.

[0015] The amount of polyglycerol condensed ricinoleic acid ester used during the heating is not particularly limited as long as it is an amount that can suppress the deterioration of texture due to cold thawing of frozen vegetables, but for example, when stir-frying or grilling, it is usually 0.001 to 2 parts by mass, preferably 0.005 to 0.5 parts by mass, per 100 parts by mass of vegetables. When boiling, it varies depending on the amount of boiling water used, but for example, when boiling using boiling water in an amount 10 times the mass of the vegetables, it is usually 0.01 to 20 parts by mass, preferably 0.05 to 5 parts by mass, per 100 parts by mass of vegetables.

[0016] The heating temperature is not particularly limited, but for example, when stir-frying, the product temperature of the vegetables is usually 50 to 100° C., preferably 60 to 90° C. When grilling, the ambient temperature is usually 140 to 240° C., preferably 160 to 200° C. When boiling, the temperature of the boiling water is usually 90 to 100° C., preferably 95 to 100° C.

[0017] The heating time is not particularly limited, but for example, when frying, it is usually 1 to 6 minutes, preferably 2 to 4 minutes. For example, when baking, it is usually 1 to 8 minutes, preferably 2 to 6 minutes. For example, when boiling, it is usually 1 to 8 minutes, preferably 1 to 3 minutes.

[0018] The heating is preferably carried out in the presence of tocopherol in addition to the polyglycerol condensed ricinoleate. By heating vegetables in the presence of the polyglycerol condensed ricinoleate and tocopherol, the deterioration of texture due to cold thawing of the frozen vegetables obtained by subsequent freezing is further suppressed.

[0019] The tocopherol is not particularly limited as long as it is one that is commonly used in foods, but examples thereof include dl-α-tocopherol (food additive), d-α-tocopherol (food additive), d-γ-tocopherol (food additive), d-δ-tocopherol (food additive), mixed tocopherols (food additive), etc.

[0020] Examples of the mixed tocopherols include tocopherols recovered from deodorized distillates (e.g., deodorized scum, deodorized sludge, hotwell oil, etc.) produced as by-products in the process of refining vegetable oils, etc. Specific examples include d-α-, d-β-, d-γ-, d-δ-tocopherols obtained by separating and refining deodorized distillates of canola oil, sesame oil, rice bran oil, safflower oil, soybean oil, corn oil, rapeseed oil, palm oil, sunflower oil, cottonseed oil, peanut oil, etc., and mixtures containing d-α-, d-β-, d-γ-, d-δ-tocotrienols, which are homologues of tocopherol, etc.

[0021] The method of carrying out the heating in the presence of polyglycerol condensed ricinoleate and tocopherol is not particularly limited as long as the polyglycerol condensed ricinoleate and tocopherol are in contact with the vegetables during heating, and examples of the method include stir-frying vegetables using fats and oils in which polyglycerol condensed ricinoleate and tocopherol are dispersed as frying oil. For example, when baking, examples include a method in which vegetables are evenly coated with fats and oils in which polyglycerol condensed ricinoleate and tocopherol are dispersed, and the vegetables are baked in an oven or the like. For example, when boiling, examples include a method in which vegetables are boiled using water in which polyglycerol condensed ricinoleate and tocopherol are mixed as the boiling water.

[0022] When the heating is performed in the presence of polyglycerol condensed ricinoleic acid ester and tocopherol, the amount of tocopherol used is not particularly limited as long as it is an amount that can suppress the deterioration of the texture of frozen vegetables due to cold thawing, but for example, when frying or baking, it is usually 0.0002 to 0.4 parts by mass, preferably 0.001 to 0.1 parts by mass, per 100 parts by mass of vegetables. When boiling, it varies depending on the amount of boiling water used, so it cannot be generalized, but for example, when boiling using boiling water in an amount 10 times the mass of the vegetables, it is usually 0.002 to 4 parts by mass, preferably 0.01 to 1 part by mass, per 100 parts by mass of vegetables.

[0023] [Process 2] Step 2 is a step of freezing the vegetables heated in step 1. In step 2, the freezing conditions are not particularly limited as long as they are general freezing conditions for vegetables, and the freezing temperature is, for example, usually −50 to −5° C., and preferably −35 to −25° C. Freezing methods include, for example, slow freezing and quick freezing, and quick freezing is preferred from the viewpoint of suppressing deterioration in texture due to cold thawing of frozen vegetables.

[0024] The production method of the present invention may include any step other than steps 1 and 2. For example, an optional step carried out between steps 1 and 2 may include a step of cooling the vegetables heated in step 1.

[0025] The method for thawing the frozen vegetables obtained by the production method of the present invention may be any general method for thawing frozen vegetables, such as natural thawing at room temperature, thawing in a refrigerator, thawing in a microwave oven, thawing in running water or in a hot water bath, etc.

[0026] The manufacturing method of the present invention can be preferably carried out when manufacturing frozen prepared foods using vegetables as raw materials. The prepared foods are not particularly limited, but examples thereof include chinjaorousu (fried pork with green onions), champon (champon), tanmen (fried noodles with broth and vegetables), hikororo (fried pork with broth and vegetables), mapo tofu (fried vegetables with broth and vegetables), and the like.

[0027] The production method of the present invention will be described below with reference to examples. However, these are merely for the purpose of explaining the production method of the present invention and are not intended to limit the production method of the present invention. EXAMPLES

[0028] [Production of frozen stir-fried bean sprouts] (1) Manufacturing Example 1 10 g of rapeseed oil (trade name: rapeseed salad oil; manufactured by Boso Oil & Fat Co., Ltd.) and 0.1 g of polyglycerol condensed ricinoleic acid ester (trade name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) were mixed to prepare a stir-frying oil. The stir-frying oil was heated in a frying pan, 200 g of bean sprouts were added thereto, and the mixture was stir-fried at a product temperature of 75°C for 2 minutes and 30 seconds while stirring with a spatula so that the stir-frying oil was evenly mixed with the bean sprouts. Then, 2.4 g of salt was added and the mixture was stir-fried for another minute. Next, the stir-fried bean sprouts were frozen at -30°C for 60 minutes using a quick freezer (model: 253FFB; manufactured by Yamato Reiki Kogyo Co., Ltd.) to obtain frozen stir-fried bean sprouts (Example Product 1).

[0029] (2) Manufacturing Example 2 Frozen stir-fried bean sprouts (Example 2) were obtained in the same manner as in Production Example 1, except that the amount of polyglycerol condensed ricinoleic acid ester (product name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) used was changed to 0.05 g.

[0030] (3) Manufacturing Example 3 Frozen stir-fried bean sprouts (Example 3) were obtained in the same manner as in Production Example 1, except that the amount of polyglycerol condensed ricinoleic acid ester (trade name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) used was changed to 0.25 g.

[0031] (4) Production Example 4 Frozen stir-fried bean sprouts (Example 4) were obtained in the same manner as in Production Example 1, except that the amount of polyglycerol condensed ricinoleic acid ester (trade name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) used was changed to 0.5 g.

[0032] (5) Production Example 5 Frozen stir-fried bean sprouts (Example 5) were obtained in the same manner as in Production Example 1, except that the amount of polyglycerol condensed ricinoleic acid ester (trade name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) used was changed to 1 g.

[0033] (6) Production Example 6 10 g of rapeseed oil (trade name: rapeseed salad oil; manufactured by Boso Oil & Fat Co., Ltd.), 0.1 g of polyglycerol condensed ricinoleic acid ester (trade name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.), and 0.02 g of tocopherol (trade name: Riken E Oil 700; manufactured by Riken Vitamin Co., Ltd.) were mixed to prepare a stir-frying oil. The stir-frying oil was heated in a frying pan, 200 g of bean sprouts were added thereto, and the mixture was stir-fried at a product temperature of 75°C for 2 minutes and 30 seconds while stirring with a spatula so that the stir-frying oil was evenly mixed with the bean sprouts. Then, 2.4 g of salt was added and the mixture was further stir-fried at a product temperature of 75°C for 1 minute. Next, the stir-fried bean sprouts were frozen at -30°C for 60 minutes using a quick freezer (model: 253FFB; manufactured by Yamato Reiki Kogyo Co., Ltd.) to obtain frozen stir-fried bean sprouts (Example Product 6).

[0034] (7) Production Example 7 Frozen stir-fried bean sprouts (comparison example 1) were obtained by treating in the same manner as in Production Example 1, except that 1 g of propylene glycol fatty acid ester (product name: Rikemal PS-100; manufactured by Riken Vitamin Co., Ltd.) was used instead of 0.1 g of polyglycerol condensed ricinoleic acid ester (product name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.).

[0035] (8) Production Example 8 10g of rapeseed oil (product name: rapeseed salad oil; manufactured by Boso Oil Co., Ltd.) was heated in a frying pan, 200g of bean sprouts were added, and the mixture was stir-fried at a product temperature of 75°C for 2 minutes and 30 seconds while stirring with a spatula so that the rapeseed oil was evenly mixed with the bean sprouts. 2.4g of salt was then added and the mixture was further stirred for 1 minute to obtain stir-fried bean sprouts. Next, 0.1g of polyglycerol condensed ricinoleic acid ester (product name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) was added to the stir-fried bean sprouts and mixed evenly. Next, the stir-fried bean sprouts were frozen at -30°C for 60 minutes using a quick freezer (model: 253FFB; manufactured by Yamato Reiki Kogyo Co., Ltd.) to obtain frozen stir-fried bean sprouts (comparative example 2).

[0036] (9) Production Example 9 Frozen stir-fried bean sprouts (Control Product 1) were obtained in the same manner as in Production Example 1, except that 0.1 g of polyglycerol condensed ricinoleic acid ester (trade name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) was not used.

[0037] [Evaluation of the texture of frozen stir-fried bean sprouts after thawing] The resulting frozen stir-fried bean sprouts (Example products 1 to 6, Comparative examples 1 and 2, and Control product 1) were thawed by heating in a microwave oven at 700 W for 1 minute 30 seconds, and then eaten, and a sensory evaluation test was conducted. In the test, evaluations were conducted by 10 panelists according to the evaluation criteria shown in Table 1, and the average evaluation points were calculated and coded according to the following criteria. The results are shown in Table 2. ◎: Average score 3.5 or higher ○: Average score 2.5 or more, less than 3.5 △: Average score 1.5 or more, less than 2.5 ×: Average score less than 1.5

[0038] [Table 1]

[0039] [Table 2]

[0040] As is clear from the results, the frozen stir-fried bean sprouts obtained by the manufacturing method of the present invention (Example products 1 to 6) were excellent, with results of "good" or better. In contrast, the frozen stir-fried bean sprouts obtained by the manufacturing method of the comparative examples (Comparative examples 1 and 2) were rated "good" and inferior to those obtained by the manufacturing method of the present invention.

[0041] [Production of frozen roasted bean sprouts] (1) Manufacturing Example 10 9.9 g of rapeseed oil (product name: rapeseed salad oil; manufactured by Boso Oil Co., Ltd.) and 0.1 g of polyglycerol condensed ricinoleic acid ester (product name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) were mixed, and the mixture was added to 200 g of bean sprouts and mixed uniformly. The bean sprouts were baked for 4 minutes at an internal temperature of 180°C using a steam convection oven (model: SCC WE101; manufactured by Rational Japan Co., Ltd.). Next, the baked bean sprouts were frozen at -30°C for 60 minutes using a quick freezer (model: 253FFB; manufactured by Yamato Reiki Kogyo Co., Ltd.) to obtain frozen baked bean sprouts (Example 7).

[0042] (2) Manufacturing Example 11 Rapeseed oil (trade name: rapeseed salad oil; manufactured by Boso Oil Co., Ltd.) 9.88 g, polyglycerol condensed ricinoleic acid ester (trade name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) 0.1 g, and tocopherol (trade name: Riken E Oil 700; manufactured by Riken Vitamin Co., Ltd.) 0.02 g were mixed, and the mixture was added to 200 g of bean sprouts and mixed uniformly. The bean sprouts were baked for 4 minutes at an internal temperature of 180°C using a steam convection oven (model: SCC WE101; manufactured by Rational Japan Co., Ltd.). Next, the baked bean sprouts were frozen at -30°C for 60 minutes using a quick freezer (model: 253FFB; manufactured by Yamato Reiki Kogyo Co., Ltd.) to obtain frozen baked bean sprouts (Example 8).

[0043] (3) Manufacturing Example 12 Frozen roasted bean sprouts (Control Product 2) were obtained in the same manner as in Production Example 10, except that 0.1 g of polyglycerol condensed ricinoleic acid ester (trade name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) was not used.

[0044] [Evaluation of the texture of frozen roasted bean sprouts after thawing] The resulting frozen roasted bean sprouts (Examples 7 and 8, and Control 2) were thawed in a microwave oven at 700W for 1 minute 30 seconds, and then eaten and subjected to a sensory evaluation test. In the test, 10 panelists evaluated the bean sprouts according to the evaluation criteria shown in Table 3, and the average score was calculated and coded according to the following criteria. The results are shown in Table 4. ◎: Average score 3.5 or higher ○: Average score 2.5 or more, less than 3.5 △: Average score 1.5 or more, less than 2.5 ×: Average score less than 1.5

[0045] [Table 3]

[0046] [Table 4]

[0047] As is clear from the results, the frozen roasted bean sprouts obtained by the manufacturing method of the present invention (Examples 7 and 8) achieved excellent results of "good" or better.

[0048] [Production of frozen boiled bean sprouts] (1) Manufacturing Example 13 2000g of water and 1g of polyglycerol condensed ricinoleic acid ester (product name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) were added to a pot, stirred for 30 seconds, and heated to boiling. 200g of bean sprouts were then added and boiled for 2 minutes while stirring. The boiled bean sprouts were then frozen at -30°C for 60 minutes using a quick freezer (model: 253FFB; manufactured by Yamato Reiki Kogyo Co., Ltd.) to obtain frozen boiled bean sprouts (Example Product 9).

[0049] (2) Manufacturing Example 14 2000g of water, 1g of polyglycerol condensed ricinoleic acid ester (product name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.), and 0.2g of tocopherol (product name: Riken E Oil 700; manufactured by Riken Vitamin Co., Ltd.) were added to a pot, stirred for 30 seconds, and heated to boiling. Then, 200g of bean sprouts were added and boiled for 2 minutes while stirring. Next, the boiled bean sprouts were frozen at -30°C for 60 minutes using a quick freezer (model: 253FFB; manufactured by Yamato Reiki Kogyo Co., Ltd.) to obtain frozen boiled bean sprouts (Example Product 10).

[0050] (3) Manufacturing Example 15 Frozen boiled bean sprouts (Control Product 3) were obtained in the same manner as in Production Example 13, except that 1 g of polyglycerol condensed ricinoleic acid ester (trade name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) was not used.

[0051] [Evaluation of the texture of frozen boiled bean sprouts after thawing] The resulting frozen boiled bean sprouts (Examples 9 and 10, and Control 3) were thawed in a microwave oven at 700W for 1 minute 30 seconds, and then eaten and subjected to a sensory evaluation test. In the test, 10 panelists evaluated the samples according to the evaluation criteria shown in Table 5, and the average score was calculated and coded according to the following criteria. The results are shown in Table 6. ◎: Average score 3.5 or higher ○: Average score 2.5 or more, less than 3.5 △: Average score 1.5 or more, less than 2.5 ×: Average score less than 1.5

[0052] [Table 5]

[0053] [Table 6]

[0054] As is clear from the results, the frozen boiled bean sprouts obtained by the manufacturing method of the present invention (Examples 9 and 10) achieved excellent results of "good" or better.

Claims

1. A method for suppressing deterioration in texture of frozen vegetables due to cold thawing, comprising carrying out the following steps 1 and 2: Step 1: Heating vegetables in the presence of polyglycerol condensed ricinoleic acid ester Step 2: Freezing the vegetables cooked in step 1

2. A method for producing frozen vegetables, comprising the following steps 1 and 2. Step 1: Heating vegetables in the presence of polyglycerol condensed ricinoleate and tocopherol Step 2: Freezing the vegetables cooked in step 1

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