JP2006271352A - Method for producing frozen food - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing frozen food excellent in hygienic safety and working efficiency, and in more details, suppressing drip occurrence in thawing through performing heat treatment and at the same time previously decreasing water in vegetables using superheated steam. <P>SOLUTION: This method for producing the frozen food comprises previously decreasing during heat treatment water produced when thawing through using superheated steam in a heating process when producing the frozen food so as to suppress drip occurrence in thawing. The frozen food obtained by the method has not only decreased risk of microbial contamination but also characteristics of improving working efficiency and hardly making processing equipments dirty because of producing almost no drip. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a method for producing frozen foods with excellent hygiene safety and work efficiency, and more specifically, by using a superheated steam to reduce the moisture in the vegetable at the same time as the heat treatment, the occurrence of drip at the time of thawing. The present invention relates to a method for producing frozen foods to be suppressed.

In recent years, food poisoning incidents due to harmful microorganisms such as O-157, Staphylococcus aureus, and Salmonella have frequently occurred, and the microbial safety of food is regarded as important. In addition, due to diversification of consumer needs, growing gourmet tastes, and growing interest in food safety and safety, the food industry and retail stores are additive-free, high-quality, and sanitary and safe work efficiency. Good frozen food is demanded.

When the vegetables are frozen in the raw state, ice crystals that become coarse during freezing damage the cell walls of the vegetables, and the fibers shrink accordingly. Therefore, when thawing, the tissue becomes spongy, and moisture is released from the tissue with reduced water retention, resulting in free water containing nutrient components, and a phenomenon of oozing from the thawed vegetable occurs. This is generally called drip. In addition, drip at the time of thawing causes enzymes such as polyphenol oxysidase, lipoxygenase, lipase to flow out of the cell at the same time, which promotes oxidation reaction, hydrolysis, etc., causing discoloration of food and deterioration of flavor. .

Since the drip generated when thawing frozen foods contains a lot of nutrients such as amino acids and sugars, the risk of microbial contamination increases. Furthermore, the thawed food is not only bad in appearance due to its high moisture content, but also has a problem in that it requires careful handling, easily contaminates the manufacturing machine, and has poor work efficiency.

For frozen foods of vegetables, blanching treatment is generally performed to prevent quality deterioration upon thawing. Blanching refers to heat treatment with hot water or steam for a short period of time used for the primary treatment of agricultural, aquatic and livestock products, and is a process performed for the purpose of sterilizing fresh ingredients or raw materials that have been peeled off or deactivating enzymes. is there. In agricultural processing, blanching is carried out to prevent discoloration by polyphenol oxidase activated after cleaving or peeling, lipid degradation by lipoxygenase, vitamin C degradation by ascorbate oxidase, decomposition of components due to metabolism after harvesting, etc. (For example, refer nonpatent literature 1). In addition, blanching has an effect of suppressing cell damage due to coarsening of ice crystals during freezing by swelling and hardening pectin and cellulose, which are constituents of the cell wall (see, for example, Non-Patent Document 2).
Frozen Vol. 62, no. 720 p98-107 (1987) New Food Industry Vol. 30, no. 4 p60-72 (1988)

Blanching is a simple processing method for suppressing deterioration of physical properties during thawing of vegetables, but its effect is not always sufficient. Therefore, the manufacturing process has been improved, and heating, freezing, and thawing techniques have been devised. There are two main methods. The former is a method of shortening the heat treatment time by using microwaves, far-infrared rays, or the like, thereby shortening the heat treatment time and suppressing physical property deterioration such as fiber weakening and swelling due to heating of the food. The latter is freezing in brine, contact freezing, or immersing in a refrigerant such as ethanol cooled below the freezing point to finish freezing in as short a time as possible. By passing through the temperature zone where the ice crystals become coarse as soon as possible, the ice crystals become coarse and the structure is prevented from being damaged.

On the other hand, methods such as the addition of food materials, pH adjusters, water retention agents, sugars or sugar alcohols, and coating of edible films before and after blanching have been devised to prevent physical property deterioration and drip spillage during thawing. ing. For example, a method for improving water retention during freezing and thawing by adding a thickening polysaccharide when producing frozen foods (see, for example, Patent Document 1), a thickening polysaccharide protective agent for pretreatment for freezing foods, And a method for preventing drip at the time of thawing by coating with sugar (see, for example, Patent Documents 2, 3, and 4), and a method for curing the fiber by changing pH and maintaining physical properties (for example, Non-Patent Document 3).
JP-A-8-317780 JP-A-5-3777 JP 9-47218 A JP-A-7-99882 Journal of Japanese Society of Nutrition and Food, Vol. 36, no. 4, p219-224 (1983)

Drip when thawing frozen food produced by rapid heat treatment or freezing treatment can be expected to have a certain effect compared to conventional blanching treatment, but the tissue damage due to coarsening of ice crystals is completely Since it cannot be prevented, drip during thawing cannot be suppressed. In addition, the suppression of drip caused by additives causes problems such as flavor deterioration and changes, product stickiness, and product sticking. Furthermore, since the labeling of additives is essential, it tends to be avoided from recent consumers.

The present invention relates to a solution to the problem of reducing the occurrence of drip that occurs when thawing frozen foods, and more particularly, using superheated steam in a heating step when producing frozen foods, and water generated during thawing. Is reduced in advance during the heat treatment, thereby suppressing the occurrence of drip during thawing. Furthermore, in the present invention, no additive is required, and this is an excellent method in which no change in flavor or stickiness occurs when an additive is added. Moreover, since the frozen food obtained by these methods hardly generates drip, it not only reduces the risk of microbial contamination, but also has the characteristics that work efficiency is improved and processing equipment is not easily soiled.

The present invention is based on the discovery that the vegetables are heated with superheated steam and the drip at the time of thawing is suppressed by performing a freezing process after reducing the water content within a specific range. That is, in the present invention, when freezing a vegetable, the water content is reduced to 60 to 90% by weight, and more preferably 65 to 85% by weight, so that the amount of free water is reduced by freezing water. By preventing the ice crystals from becoming coarse, physical property deterioration and drip prevention at the time of thawing are achieved. In addition, the conditions of the superheated steam treatment for obtaining the optimum physical properties vary depending on the type of vegetable.

The vegetables used in the present invention are not limited, but are intended for root vegetables, and more specifically selected from the group consisting of carrots, radish and potatoes.

The vegetable used by this invention uses what was cut-processed. Although the size and shape after the cutting are arbitrary, a die shape, a small piece shape, a ring shape or the like having a side of 3 cm or less is desirable. This is due to the characteristic food temperature change in the superheated steam treatment. Specifically, it is an optimum shape derived from a rapid rise in the temperature of the surface and a slow rise in the temperature, and is obtained from the balance between the drying of the surface and the rise in the temperature inside. Heating and drying are performed in a well-balanced shape with a side of 3 cm or less. However, when the shape has a side of 3 cm or more, it takes time to increase the internal temperature, leading to surface drying, which is not preferable in terms of product quality.

The superheated steam used in the present invention is obtained by further heating a saturated steam at 100 ° C. under normal pressure. The method for generating superheated steam is obtained by passing water or steam supplied from a circulating boiler through a superheated steam can, a ceramic body heated by electromagnetic induction, or a carbon material.

For the superheated steam treatment of the cut vegetables, either a batch type or a continuous type processing apparatus can be used, but it is preferable to use a continuous type processing apparatus. By continuously supplying superheated steam to the continuous processing apparatus, the inside of the processing section can be maintained almost oxygen-free, and thus coloring and oxidation due to oxygen can be suppressed.

In the present invention, the cut vegetables are heated using superheated steam, and at the same time the moisture content is reduced to 60 to 90% by weight (hereinafter abbreviated as%), more preferably 65 to 85%, followed by freezing. Apply. If the water content after the heat treatment is 60% or less, drip at the time of thawing does not occur, but the shrinkage of the tissue becomes remarkable, so that the physical properties become hard and the texture becomes rubbery. Furthermore, a decrease in yield on a product basis becomes a problem and is not practical. On the other hand, when the water content after the heat treatment is 90% or more, the water is not sufficiently reduced, and drip is generated at the time of thawing, so that the effect of the present invention is small. However, the superheated steam treatment conditions for obtaining the optimum physical properties vary depending on the type of vegetable.

The above-mentioned superheated steam treatment is 100 ° C. or higher, and the heating time is not limited, but the treatment conditions are preferably the shortest time that can achieve the water content. For example, when the amount of steam of superheated steam is about 250 kgf / m ² per hour, the temperature condition is 110 to 200 ° C., preferably 130 to 180 ° C., and the treatment time is 2 to 10 minutes, preferably 4 to 8 Minutes are desirable. However, the above processing conditions vary depending on the amount of steam per hour. When the amount of steam increases, a low temperature setting and a short time treatment are required. When the amount of steam decreases, a high temperature setting and a long time processing are necessary. It becomes.

Vegetables that have been heat-treated are immediately frozen. The freezing method is not particularly limited, but a cooling air method such as a blower type, a tube shelf type, a brine cooling method, a contact freezer, a steel belt cooling and other contact freezing methods can be exemplified. It is desirable to pass through a temperature range where ice crystals become coarse as soon as possible.

The present invention is a method for producing frozen food, wherein superheated steam is used in the heating process when producing frozen food, and moisture generated during thawing is reduced in advance during heat treatment, and the effect of suppressing drip during thawing There is.

Furthermore, in the present invention, no additive is required, and this is an excellent method in which no change in flavor or stickiness occurs when an additive is added. In addition, since the frozen food obtained by these methods greatly reduces the occurrence of drip, it not only reduces the risk of microbial contamination, but also has the effect of improving work efficiency and preventing the processing equipment from becoming dirty.

FIG. 1 is a block diagram showing an example of an embodiment of the present invention. Supply unit 4 that can supply a certain amount of cut vegetables per unit time, heating medium supply unit 2 that can supply superheated steam at a predetermined temperature, heating unit 1 that fills the interior with superheated steam and heats the cut vegetables, and after heat treatment The discharge section 5 for receiving the cut vegetables and the cooling section 6 for cooling or freezing the discharged cut vegetables. The transport unit 3 moves the cut vegetables between the supply unit 4, the heating unit 1, the discharge unit 5, and the cooling unit 6, and the heating unit 1 performs a superheated steam treatment at a predetermined steam supply amount, temperature, and time. To do.

A fixed amount of the cut vegetables is supplied from the supply unit 4 to the transport unit 3 per hour. The conveyance unit 3 passes through the heating unit 1 heated to a predetermined temperature by superheated steam supplied from the heat medium supply unit 2. The cut vegetables are processed by the heating unit 1 with superheated steam for a predetermined time by the transport unit 3 and then discharged to the discharge unit 5. This form can process continuously cut vegetables.

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

The carrots were used to compare the drip and physical properties of the cut vegetables produced by hot water blanching and heating with superheated steam.

In this apparatus, a recirculating boiler was used as a steam generation source, and the supplied steam was further reheated through a super heater (manufactured by Miura Kogyo Co., Ltd.) to obtain superheated steam. The amount of steam in the heat treatment is 250 kgf / m ² per hour.

First, the weight change when superheated steam treatment was performed was examined using carrots that were cut. In the test, carrots were peeled off and carrots with a side cut to 15-18 mm were used. 300 g of the cut carrot was passed through a belt conveyor type continuous superheated steam treatment apparatus and subjected to heat treatment, and the change in weight over time was determined. The temperature of superheated steam was 140, 160, and 200 ° C, and hot water blanching at 90 ° C was performed as a control.

FIG. 2 is a graph of the change in weight due to superheated steam treatment when hot water blanching is used as a control. Hot water blanching was performed at 90 ° C. In hydrothermal blanching, the change in weight was small before and after heating, and decreased by about 3%. On the other hand, in the superheated steam treatment, the weight decreased with time, and the higher the temperature, the greater the decrease in weight. In any heating temperature range, the heat treatment is preferably about 4 minutes, but on the other hand, the superheated steam at a high temperature exceeding 220 ° C caused the problem of carbonization of the carrot tip during the heat treatment. Then, it turned out that too high temperature superheated steam is not preferable.

Next, the drip test at the time of thawing was performed using the cut carrot. In the test, carrots were peeled off and carrots with a side cut to 15-18 mm were used. 300 g of the cut carrot was passed through a belt conveyor type continuous superheated steam treatment apparatus, subjected to heat treatment, and the weight was measured. After the heat treatment, it was quickly cooled, the whole amount was sealed in a polypropylene bag, and then frozen at −20 ° C. by air cooling. After freezing for several days, natural thawing was performed in a thermostatic chamber at 15 ° C., and the weight after discharging the drip was measured. As controls, 90 ° C. hot water blanching and 90 ° C. steam blanching were also performed.

FIG. 3 shows the weights after heat treatment and thawing when the weight of the cut vegetables is 100. The heat treatment was performed by hot water blanching for 10 minutes, steam blanching for 10 minutes, and superheated steam at 170 ° C. for 2, 4, and 6 minutes.

When the raw cut carrot was frozen and thawed, a drip of 15% of the raw weight was generated, and the physical properties were also sponge-like. In the hot water blanching, the weight decreased by about 3% after the heat treatment, and a drip of about 5% occurred at the time of thawing. In steam blanching, the weight decreased by about 7% after the heat treatment, and a drip of about 8% occurred during thawing.

On the other hand, in the sample subjected to the superheated steam treatment at 170 ° C., the longer the treatment time, the greater the weight loss after the heat treatment, 12% for 2 minutes treatment, 17% for 4 minutes treatment, and 27% for 6 minutes treatment. Weight decreased. Further, the drip at the time of thawing produced a drip of about 5% because the heat treatment was not sufficiently performed in the 2-minute treatment and the decrease in the water content was small. However, drip at the time of thawing hardly occurs at 1% or less under the condition of treatment for 4 minutes or more. From these results, it became clear that drip at the time of thawing can be suppressed by reducing moisture during the heat treatment. In addition, in the treatment for 8 minutes or more, there was almost no drip at the time of thawing, but since the weight of the product was remarkably reduced and the texture became rubbery by drying, the heat treatment for 8 minutes or more is not preferable. all right.

Furthermore, the sugar content of the cut carrots at the time of thawing was compared. After crushing the sample, sugar was extracted with 80% ethanol, diluted appropriately and filtered to prepare a sample solution. The obtained sample solution was analyzed using high performance liquid chromatography, and glucose, sucrose, and fructose were quantified, and the total amount was defined as the sugar content.

FIG. 4 shows the sugar content in carrots after each heat treatment. Raw cut carrots contained 5.6% sugar, but after hot water blanching, the sugar content was reduced to 4.2% due to spillage during cooking, and steaming blanching was the same. The sugar content was reduced to 3.1% because the sugar content flowed out with the moisture condensed by the steam. On the other hand, condensed water is not generated in the superheated steam treatment, and the moisture content is reduced by the heat treatment, so that the sugar content is relatively concentrated, 6.1% in the 2-minute treatment, and 6.8% in the 4-minute treatment. , 6 minutes treatment contained 7.8% sugar, 1.2 to 1.4 times as much sugar as raw cut carrots. Even when actually eaten, it became a product with a rich carrot flavor.

A drip test at the time of thawing was performed using a cut radish. The test was performed in the same manner as in Example 1.

FIG. 5 shows the weight after heat treatment and thawing when the weight of the cut radish is 100. The heat treatment was performed under conditions of hot water blanching at 90 ° C., steam blanching at 90 ° C., and superheated steam at 170 ° C. for 4, 6, 8, and 10 minutes.

When the raw cut radish was frozen and thawed, a drip of 24% of the raw weight was generated, and the physical properties were also sponge-like. In the hot water blanching, the weight decreased by about 6% after the heat treatment, and a drip of about 19% occurred at the time of thawing. In steam blanching, the weight decreased by about 9% after the heat treatment, and drip of about 20% occurred during thawing.

On the other hand, in the radish subjected to the superheated steam treatment at 170 ° C., the longer the treatment time, the greater the weight loss after the heat treatment, 19% for the 4-minute treatment, 27% for the 6-minute treatment, 40% for the 8-minute treatment, A 10% treatment resulted in a 53% weight loss. Further, the drip at the time of thawing was not sufficiently heat-treated in the 4-minute and 6-minute treatments, and a drip of about 10% was generated because the decrease in the water content was small. However, the drip at the time of thawing hardly occurs at 1% or less under the condition of treatment for 8 minutes or more. From these results, it became clear that the cut radish can suppress the drip at the time of thawing by heat treatment at 170 ° C. for 8 minutes. In addition, the heat treatment for 10 minutes or more caused almost no drip upon thawing, but the weight of the product was remarkably reduced, the texture became rubbery by drying, and carbonization of the surface was observed for 10 minutes. It turned out that the above heat processing is not preferable.

The present invention can provide a frozen food in which drip is suppressed after thawing.

The block diagram which showed an example of embodiment of this invention A graph showing the change in time and weight after heat treatment of cut carrots Graph showing the weight after each heat treatment using cut carrots and the change in weight upon thawing Graph showing sugar content after each heat treatment of cut carrot Graph showing the weight after each heat treatment using cut radish and the change in weight when thawing

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heating part 2 Superheated steam supply part 3 Conveying part 4 Supply part 5 Discharge part 6 Cooling part

Claims (3)

A method for producing frozen food, characterized by suppressing drip generated at the time of thawing by performing a superheated steam treatment on the cut vegetables and performing a freezing treatment after reducing the moisture simultaneously with the heat treatment The cut vegetable according to claim 1, wherein the vegetable is selected from the group consisting of carrot, radish and potato. The frozen food according to claim 1, wherein the moisture content of the vegetables cut by the superheated steam treatment is adjusted to 60 to 90% by weight.

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