JPS61280256A - Production of dried food having good reconstitution property - Google Patents

Abstract

PURPOSE:To obtain the tilted food, having a high reconstitution rate and suitable for instant noodles, etc., by quickly freezing a food with a high moisture content and dehydrating the water in the food with ethanol or methanol at temperature of the freezing point of the water contained in the food or below. CONSTITUTION:A food with a high moisture content, e.g. raw or cooked vegeta ble with >=60wt% moisture content, is quickly frozen, preferably at -30--100 deg.C for <=10min, and water contained in the food is dehydrated with ethanol methanol, preferably ethanol at a temperature of the freezing point of the water or below, e.g. <=-1 deg.C, to afford the aimed food.

Description

[Detailed Description of the Invention] [Industrial Application Field] In recent years, with changes in lifestyle, there has been a demand for a more flexible diet. In particular, the production of dried foods, which return to their original state by simply adding water or hot water, is showing remarkable growth.

Dried foods are characterized not only by their convenience but also by their very long shelf life, such as instant noodles, instant vegetables, and dried vegetables.゛The present invention relates to a method for producing such a highly restorable dried food.

[Conventional technology and problems]

Conventionally, hot air drying and heat drying methods using contact with other heat carriers are well known as methods for producing dried foods. However, since this method changes the food during drying, the food after drying does not easily return to its original state even if water or hot water is added to it; The time is also long. Therefore, in order to shorten the restoration time, techniques have been developed to make food porous. In other words, the extruder method is a method in which food is heated under high pressure and then rapidly reduced in pressure.
This includes the puffing machine method. This method shortens the restoring time, but since a heating step is involved, the physical properties change and the restoring performance is poor. In particular, it cannot be used on raw vegetables.

In recent years, freeze-drying has been put into practical use in order to improve these shortcomings, and it has become possible to obtain dried foods with short reconstitution time and good reconstitution properties, but it is expensive due to expensive equipment and operating costs. It has the disadvantage of being expensive.

On the other hand, an invention has been proposed (Japanese Unexamined Patent Publication No. 52-48840) in which the alcohol dehydration method, which is commonly used for preparing samples for biological observation, is used as a drying method for pregelatinized starch foods. Even if repeated attempts are made, the present situation is that in food tissues with high water content, 'fJLm is destroyed during dehydration and a good porous material cannot be obtained, and satisfactory restorability cannot be obtained.

The present inventors have completed the present invention as a result of extensive research into a method for producing dried foods that can be produced at low cost, have a fast restoring speed, and have excellent restorability. [To solve the problems] ] That is, in the present invention, after rapidly freezing foods with high moisture content,
The present invention relates to a method for producing a dry food with good restorability, which comprises dehydrating the water in the food using ethanol or methanol at a temperature below the freezing point of the water in the food.

Since the method of the present invention causes extremely little damage to tissues during dehydration, it can also be applied to the preparation of dried specimens of living organisms.

The term "food with high moisture content" that is the object of the present invention refers to foods or food materials with a moisture content of at least 60% by weight or more. For example, raw or cooked vegetables, fruits,
Examples include mushrooms, beans, potatoes, fish and shellfish, and livestock meat.

Foods whose main ingredient is starch, such as noodles and grains that have been processed eight times, and gelatinized starch pastes are also subject to this process.

Next, the manufacturing method of the present invention will be explained in detail.

The present invention includes a first step of rapidly freezing foods with high moisture content;
The second step consists of dehydrating the frozen food using ethanol or methanol at a low temperature at which the ice crystals of the frozen food do not melt, that is, at a temperature below the freezing point of the water in the food.

First, the first step is to quickly freeze the water in the food to generate as small ice crystals as possible. The smaller the ice crystals are, the less tissue destruction is caused by the ice crystals, and the better the restorability after dehydration with ethanol or methanol. The conditions for quick freezing used in the present invention vary depending on the thickness of the food to be frozen, but the conditions for quick freezing used in the present invention vary depending on the thickness of the food to be frozen.
(0°C) food must be completely frozen within 10 minutes. The above conditions can be achieved for plant leaves and swollen starch granules with a thickness of 2Ⅲ or less at a low temperature of -10℃ or less, but for those with a thickness of 5 mm to 10 mm (for example, vegetables, cubed potatoes, etc.) A low temperature of -30°C or lower is required. Even thicker ones require a temperature of -50°C or less. In any case, it is desirable to slice, thin, or powder the food to be frozen, as long as the texture and appearance are not affected. Furthermore, the lower the freezing temperature, the more effective it is, but it is usually desirable to have a freezing temperature of -30 to -100°C. Slow freezing, which requires 10 minutes or more to completely freeze, causes ice crystals to become coarser, resulting in reduced restorability. Freezing methods include (1) immersion in a cooled solvent (acetone, alcohol, etc.);
(2) spraying with or immersion in cryogenic liquefied gas such as liquid nitrogen or liquid air; (3) immersion in brine; (4) contact with cooling metal plates and other media. (5) method using cooling air, etc. All of these freezing methods (1) to (5) can be used in the present invention, but method (1) is the most desirable. In the case of method (1), if ethanol or methanol is used as the solvent, the solvent is first cooled to a temperature that does not solidify (-10°C to -80°C), the food is immersed in this, and the food is quickly and completely frozen. Thereafter, the food can be heated to a temperature at which the ice crystals in the food do not melt (usually -5°C to -1°C) for alcohol dehydration. That is, the method (1) has the advantage that the first step and the second step can be performed consecutively.

Ethanol or methanol is used as a dehydrating agent in the second step of the present invention, but ethanol is preferable because the object is food. In the second step, ethanol or methanol kept at a temperature below the freezing point of water in food is
Add excess to frozen food and dehydrate with the alcohol while stirring. The temperature at this time is usually -1℃ or lower, but if it contains sugars, the freezing point will drop, so the temperature will be -5℃.
Temperatures below ℃ may be required.

By this operation, fine ice crystals formed between tissues in food can be dissolved in alcohol (ethanol or methanol) without destroying the tissues, and at the same time, the alcohol fixes the tissues extremely. A porous food with good resilience is formed. When freezing slowly, ice crystals grow during freezing and tissue is destroyed. Furthermore, if the water in the food is dehydrated using the alcohol in an unfrozen state, the tissue is not frozen and fixed, so tissue destruction occurs during dehydration, making it difficult to make the food porous. Dehydration using ethanol or methanol is preferably carried out until the water content in the food becomes 10% by weight or less. Stirring during dehydration or exchanging the alcohol if the water content is large increases the dehydration rate and is effective.

After dehydration with ethanol or methanol to a water content of 10% by weight or less, ethanol or methanol is removed by filtration, centrifugation, decantation, etc., and drying is performed.

At this time, the food structure does not change no matter which drying method is used, such as heat drying, vacuum drying, microwave drying, etc.

Foods dried by the method of the present invention can be quickly restored by simply adding water or hot water, and have an appearance that closely resembles that of the food before drying.
Indicates physical properties. Furthermore, since the method of the present invention does not require expensive equipment such as a freeze dryer, dried foods can be produced at low cost.

In addition, by heating starch or grains containing starch as a main component to make it into a paste state, and then producing porous powder using the present invention, powder with extremely high water absorption and oil absorption properties can be obtained. is possible.

〔Example〕

Hereinafter, the present invention will be further explained by showing Examples and Comparative Examples.

Example 1 100 g of rice (moisture 65% by weight) cooked in a conventional manner using a rice cooker was quickly and completely frozen in a -60°C freezer for 7 minutes, and then kept at -5°C.

On the other hand, cool 1 kg of methanol to -5°C and
00g of frozen cooked rice. After dehydration for 2 hours at -5℃,
Methanol used for dehydration treatment was filtered. The cooked rice dehydrated using methanol was dried in a dryer at 105° C. for 1 hour to obtain dried cooked rice.

Comparative Example 1 100g of rice (moisture 65% by weight) cooked in the same manner as in Example 1 was quickly frozen at -60°C, kept at -5°C, and then kept at -5°C. was freeze-dried without dehydration using ethanol or methanol to obtain dry cooked rice.

Comparative Example 2 100 g of rice (moisture 65% by weight) cooked in the same manner as in Example 1 was cooled to room temperature (approximately 20° C.), and 1 kg of methanol at room temperature was added thereto to dehydrate for 2 hours. After filtering methanol, it was dried at 105° C. for 1 hour to obtain dried cooked rice.

Regarding the dry cooked rice obtained in Example 1 and Comparative Examples 1 and 2,
A sensory test (restorability evaluation test), surface observation, and manufacturing cost evaluation were conducted. The results are shown in Table 1.

0 Evaluation Method (i) Sensory Test (Restorability Evaluation Test) After adding hot water to dry cooked rice, the excess hot water was discarded and the rice was steamed for 4 minutes. This was compared with cooked rice before drying using five expert panelists.

Evaluation is on a three-level scale, with ◎, △, and × ◎; Close to cooked rice △；Less than cooking method ×; The core remains and is not edible. means.

(ii) Surface observation Surface observation using a scanning electron microscope It was.

(iii) Manufacturing cost Current equipment and operation requirements I commented on the overview of costs.

Note to Table 1) All five panelists rated the samples of Example 1 and Comparative Example 1 as ◎, and the sample of Comparative Example 2 as ×.

Example 2 Cut cabbage with a moisture content of 92% into 2cm squares, and cut into 5 pieces.
0 g was placed in ethanol heated to -50°C using dry ice and quickly and completely frozen for 5 minutes.

At this time, the amount of ethanol used for 50g of cabbage is 2
It was 00g. Next, quickly freeze the cabbage at -2°C.
After dehydrating for 1 hour, decant the ethanol and remove
200g of ethanol at -2°C was added again, and the mixture was further dehydrated for 1 hour at -2°C.

The dehydrated cabbage was taken out and vacuum dried to obtain dried cabbage.

Comparative Example 3 Cabbage with a water content of 92% by weight was cut into 2 cm squares.
0 g was placed in ethanol heated to -50°C using dry ice and quickly frozen. At this time, the amount of ethanol was 200 g per 50 g of cabbage. Next, the rapidly frozen cabbage was left at room temperature (20° C.) for 1 hour. Furthermore, 200 g of ethanol at room temperature was added, and the mixture was left to stand at room temperature for 1 hour again to dehydrate it.Then, this was vacuum dried at room temperature to obtain dried cabbage.

The dried cabbages obtained in Example 2 and Comparative Example 3 were examined for restorability. That is, water was added to dried cabbage and the state after 30 minutes was compared with fresh cabbage.

The evaluation was performed by five expert panelists. The result is the second
Shown in the table.

The evaluation is in three stages: ◎, Δ, and × mean ◎; appearance and physical properties similar to raw cabbage; △; appearance and physical properties inferior to raw cabbage; ×; almost no restoration.

All five panelists in Table 2 said that the sample of Example 3 was ◎, and the sample of Comparative Example 3 was
The sample was judged as ×.

〔Effect of the invention〕

Claims (1)

[Claims] A method for producing a dry food with good restorability, which comprises rapidly freezing a food with a high moisture content, and then dehydrating the water in the food using ethanol or methanol at a temperature below the freezing point of the water in the food.