JPH0262211B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing dried foods, and more particularly, to a method for producing dried foods, which comprises freezing the food to be dried and then applying vacuum oil to the thawed product. .

The dried food obtained by the present invention has the original flavor, color, and appearance of the raw materials, has a crispy and soft texture, and has the property of absorbing water and restoring itself in boiling water in a short time. Because there is a snack,
It is useful as a delicacy or as an ingredient in soups and noodles.

[Conventional technology] Foods dried using the vacuum oil method are dried at relatively low temperatures.
In other words, dehydration and drying is performed in oil at a temperature of 70 to 130°C under reduced pressure, so if dried under appropriate conditions, the original flavor and color of the raw material will be retained, and the structure will be porous and slightly swollen. product may be obtained. This dried product has superior color, flavor, appearance, and resiliency compared to hot air-dried products, and has a firmer tissue structure and is less likely to break down compared to freeze-dried products, and has a unique flavor caused by oil. death,
The color tone, appearance, and restorability are also comparable.

For this reason, the production of dried foods using the vacuum oil method has recently been attracting attention, but its basic principle has been known for quite some time, with literature dating back to the 1930s, and there have been many related patent applications recently. It's summery.

However, from the standpoint of product quality, industrial manufacturing methods, etc., the conventional methods cannot be said to fully utilize the basic principles, and improvements are desired.

Specifically speaking, the problems of the conventional technology are as follows: The raw material used for drying has a unique tissue structure, and even if the raw material is the same, there are differences depending on the part of the tissue itself and individual differences, and the flavor, color tone, and appearance unique to the raw material may vary. It is not possible to obtain a product that has a crunchy texture and does not have sufficient restorability when immersed in hot water. For example, many of them have a deformed or shrunken appearance and a hard, crunchy texture, making them difficult to eat as snacks or delicacies. Furthermore, the reconstitution property is also inferior to that of freeze-dried products.

As a method to solve these problems, it has been proposed to reduce the thickness of the raw material to be dried to make it easier to dry, but this method does not provide a satisfactory effect. Furthermore, a method of immersing the raw material to be dried in a solution of sugar, starch, protein, gum, etc., and reduced pressure oil conditions,
That is, methods of adjusting oil temperature and vacuum degree have been proposed, but these methods are only partial improvements. It has also been proposed to combine these methods with other drying methods, but these methods have not produced sufficiently satisfactory effects.

[Problems to be Solved by the Invention] Therefore, the problems to be solved by the present invention are as follows.

To obtain a product having a flavor, color tone, and appearance peculiar to raw materials to be dried, especially a product whose appearance is free from shrinkage or deformation and whose shape approximates the shape before drying.

To obtain a product having a crispy and soft texture.

To obtain a product which absorbs water and recovers in a short time when immersed in hot water.

To obtain a product having a thickness of about 5 to 10 mm and having the above properties.

[Means for Solving the Problems] An object of the present invention is to provide a method for producing a dried food product that overcomes all of the above-mentioned problems.

That is, in the present invention, the raw material to be dried is subjected to treatments such as trimming, shaping, and blanching as necessary, then slowly frozen, then thawed, and added to a solution of sugar, starch, protein, etc. as necessary. After immersion under reduced pressure, oil temperature 90 to 130℃, maximum degree of vacuum and water evaporation
Dry to a moisture content of 8 to 20% under conditions of 50 Torr or less, preferably 20 Torr or less, then dry at an oil temperature of 70 to 90°C and a vacuum degree of 20 Tor or less to a moisture content of 5%.
This is a method for producing dried foods, which is characterized by drying until the following:

In the present invention, the raw material to be dried is adjusted to have a structure that allows moisture to be easily volatilized from the surface and structure of the raw material by slow freezing, and then the drying material is processed into vacuum oil. In this case, in the early stage of drying, that is, until the moisture content is 8 to 20%, the raw material to be dried is dried in relatively high temperature oil, usually oil at a temperature of 90 to 130°C, for a very short time. Transform the organizational structure of
Stabilize to avoid shrinkage. Next, the water content is reduced to 5% in oil at a relatively low temperature, usually at a temperature of 70 to 90°C, without changing or losing the original color, flavor, nutrients, etc. of the raw material to be dried as much as possible.
% or less is important.

The present invention will be explained in detail below.

A wide variety of raw materials can be used as the raw material to be dried, such as vegetables, fruits, seafood, livestock meat, and cooked foods. Specifically, vegetables include potatoes,
Root vegetables rich in fiber and starch, such as sweet potatoes, carrots, and lotus; Preferably those with special tissue structures, such as bean sprouts, green beans, corn, and shiitake mushrooms. Fruits that are high in carbohydrates, such as apples, persimmons, and kiwi. Among seafood, preferred are molluscs such as squid and octopus; those having characteristic textures and tissues such as clams, clams, and scallops are preferred. Livestock meat includes beef, pork, chicken, etc., which are made of muscle fibers whose main component is protein, and cooked foods include foods made of livestock meat, vegetables, and starchy materials such as shumai, gyoza, hamburgers, and meatballs. There are some that have characteristics in feel and structure.

The above raw materials are trimmed as necessary by removing inedible parts, peeling, pulverizing, etc., blanching to deactivate enzymes, steaming to gelatinize starch, and turning into seasoning liquid for seasoning, etc. Perform immersion as appropriate.

Next, the raw material to be dried is frozen at a temperature of -15 to -30°C to generate fine ice crystals on the surface and within the structure. Freezing can be carried out, for example, by air blasting, contact freezing, or using liquid carbonic acid or liquid nitrogen.
It may be selected as appropriate in consideration of the properties of the raw material to be dried, the final quality required of the dried product, etc. It is desirable that the freezing treatment be carried out slowly and completely over a period of 5 to 15 hours, thereby forming fine ice crystals on the surface and structure of the raw material to be dried. Next, the frozen product is thawed again at room temperature or under heat to melt the ice crystals formed in the structure of the raw material to be dried, thereby creating a porous structure.

The freeze-treated and thawed product of the raw material to be dried thus obtained is immersed in a known solution of saccharides, starches, proteins, etc., if necessary. The purpose of this is to improve the drying yield, stabilize the structure, harden, expand, etc., and depending on the raw material, it can be used as an auxiliary means for the present invention. Various methods can be considered as the immersion method, such as under heating, under normal pressure, under increased pressure, and under reduced pressure, but in the present invention, it is preferable to carry out under reduced pressure from the viewpoint of adsorption into the surface and tissue of the raw material to be dried. .
This prevents deformation and collapse of the tissue and enables processing in a short time.

The thus obtained pretreated raw material to be dried is dried in a drying step using reduced pressure oil.

When selecting the conditions for the vacuum oil, it is important to keep the surface and porous structure of the raw material obtained by freezing as intact as possible while drying the raw material to be dried. color, flavor,
It is important to dry the food so that there is no change or loss of nutritional components. In other words, dehydration should be carried out as instantaneously as possible during the constant rate drying period, until the structure of the raw material to be dried is stabilized without deforming or shrinking, in other words, until the moisture content reaches approximately 8 to 20%. is necessary. Therefore, it is necessary to dehydrate at a relatively high temperature, generally in the temperature range of 90 to 130°C, and under high vacuum. in this case,
The degree of reduced pressure should be 50 Torr or less, preferably 20 Torr or less, at the time of maximum moisture evaporation. Dehydration for a relatively long period of time until the moisture content of the raw material to be dried reaches around 7 to 20% has the disadvantage that the tissue structure of the raw material to be dried tends to shrink and deform.
The advantages of the freezing treatment cannot be fully utilized, and the effects of the present invention cannot be fully achieved.

When the moisture content falls within a range of about 8 to 20% or less, the rate of volatilization of moisture from the raw material to be dried slows down, entering the so-called decreasing rate drying period. In this region, the influence of temperature becomes more pronounced as it is directly affected by oil temperature rather than the drop in product temperature due to the latent heat of vaporization of water. Therefore, in this region, it is necessary to dry at a relatively low temperature, generally 70 to 90°C. Below 70℃, the rate of moisture volatilization is slow, making it inefficient; above 90℃, raw materials with high sugar and amino acid content tend to brown, retaining the original color and flavor of the raw materials to be dried. I can't do that. In addition, the selection range of the drying end point is narrow, which causes scorching, resulting in a large difference in the quality of the dried product.

On the other hand, the degree of vacuum is preferably as high as possible, but it is necessary to maintain it at 50 Torr or less, preferably 20 Torr or less, at the time of maximum moisture evaporation. If it is outside this range, the advantage of the freezing effect of the raw material to be dried cannot be fully utilized, and the shrinkage and deformation of the structure of the raw material to be dried becomes significant, especially when the thickness of the raw material is 5 to 10 mm.

[Example] Next, the present invention will be explained by examples.

Example 1 30 kg of raw sweet potato (Kokei No. 14) was washed with water, sliced into 7.5 mm thick slices using a slicer, and then placed in boiling water and blanched for 3 minutes. Next, this was placed in a -20°C freezer for 15 hours and frozen. After freezing, the sample was left at room temperature for 5 hours to thaw, then placed in a vacuum oil device equipped with a basket-type centrifugal deoiling device, and the pressure was reduced to 15 Torr using a vacuum pump. Next, 400 g of oil (melting point: 37°C, vegetable oil) at 120°C was sent by pump. The time required for sending was 1 minute and 15 seconds. In addition, the degree of depressurization is temporarily reduced at 2 minutes and 15 seconds after the start of oil supply.
It rose to 20 Torr, but after one minute it dropped to 15 Torr and stabilized. The oil temperature dropped to 85°C 6 minutes and 30 seconds after the start of oil supply. 6 minutes and 30 seconds after the start of oil supply, oil whose temperature was adjusted to 85°C was circulated in the oil device, and 17 minutes and 30 seconds after the start of oil supply, the oil was discharged. Thereafter, the oil was removed by centrifugation at 90 rpm for 2 minutes, and after releasing the vacuum, the dried sweet potatoes were taken out. In this way, 11.5 kg of dried slices with a moisture content of 3.9% were obtained.

This product had no shrinkage or deformation in appearance, had a bright color, and had a crispy and soft texture when eaten as is. You can also add this product to boiling water for 3
After soaking for a few minutes and draining the hot water, it almost absorbed water and was restored to have the same flavor and texture as before drying.

Example 2 After washing 35 kg of kiwi with water, the slices were sliced into 10 mm thick slices using a slicer, and then placed in a -20°C freezer for 10 hours to freeze. After freezing, the temperature was adjusted to 25-30℃ (starch hydrolyzate 20%, vitamin C 0.05%,
After immersing in 80 kg of 0.2% fragrance (containing 0.2% fragrance) for 3 hours, the liquid was drained. This was placed in a vacuum oil device equipped with a basket-type centrifugal deoiling device, and the pressure was reduced to 12 Torr using a vacuum pump. Next, oil and fat at 115℃ (melting point 37℃,
(vegetable oil) 400 was pumped. The time required for delivery was 1 minute 20 seconds. The degree of vacuum rose to 18 Torr at one point 2 minutes and 45 seconds after the start of oil supply, but then decreased and stabilized at 10 to 12 Torr. Furthermore, the oil temperature dropped to 79°C 5 minutes and 30 seconds after the start of oil supply. 5 minutes and 30 seconds after the start of oil supply, oil whose temperature was adjusted to 80°C was circulated in the vacuum oil device, and the oil was discharged 15 minutes and 30 seconds after the start of oil supply. Then 110rpm
The dried kiwi was removed by centrifugation for 3 minutes, the vacuum was released, and the dried kiwi was taken out. In this way moisture content 4.2
8.1Kg of sliced dried kiwi was obtained.

The dried product had no shrinkage or deformation in appearance, had a bright color, and had a crispy and soft texture when eaten as is.

Example 3 After washing 40 kg of shelled clams with water, they were placed in boiling 3% saline solution and heated for 3 minutes. Next, this was taken out, drained, frozen in a contact freezer, and then left in a refrigerator (7° C.) for one day and night to thaw. After draining the drip, place it in a vacuum oil device with a basket-type centrifugal deoiling device, and remove it with a vacuum pump.
The pressure was reduced to 15Torr. Thereafter, 400 g of oil at 130°C (melting point 37°C, vegetable oil) was pumped into the reactor.
The time required for delivery was 1 minute and 30 seconds. The degree of vacuum rose to 18 Torr at one point 3 minutes after the start of oil supply, but then decreased and stabilized at 10 to 12 Torr. Furthermore, the oil temperature dropped to 89°C 9 minutes and 30 seconds after the start of oil supply. After 9 minutes and 30 seconds after the oil supply started, the oil adjusted to 90℃ was circulated in the decompression oil device, and after the oil supply started.
The oil was drained at 22 minutes and 30 seconds. Next, the oil was removed by centrifugation at 100 rpm for 2 minutes, and the dried clams were taken out after releasing the vacuum. In this way, 8.8 kg of dried clams with a moisture content of 3.9% were obtained.

The appearance of this dried product showed no shrinkage or deformation, and no change in color tone. When eaten as is, it had a crispy and soft texture. Also,
When this dried product was immersed in hot water for 3 minutes, it absorbed water and was restored to have a texture unique to clams.

[Effects of the Invention] The dried food obtained by the present invention has the flavor, color tone, and appearance inherent to the raw materials, and also has a crispy and soft texture. Furthermore, since this dried food has a porous tissue structure, it has the property of absorbing water and restoring itself in a short period of time when immersed in hot water. Therefore, dried foods can be eaten as-is as snacks or delicacies, and those that have been absorbed and reconstituted have a wide range of uses as ingredients for soups and noodles (ramen, udon, soba, etc.).

Claims (1)

[Claims] 1 The raw material to be dried is subjected to treatments such as trimming, shaping, and blanching as necessary, then slowly frozen, then thawed, and immersed in a solution of sugar, starch, protein, etc. under reduced pressure as necessary. After that, the oil temperature is 90~
At 130°C and under reduced pressure conditions of maximum moisture evaporation of 50 Torr or less, preferably 20 Torr or less, the moisture content is 8 to 8.
A method for producing a dried food, which comprises drying the food to a moisture content of 20%, and then drying the food at an oil temperature of 70 to 90°C and a degree of vacuum of 20 Torr or less until the moisture content is 5% or less.