SU1410932A1 - Method of freezing food products - Google Patents

Abstract

The invention relates to refrigeration engineering, in particular to methods for air freezing food products. The aim of the invention is to reduce the mass loss of the product during the freezing process by restoring the moisture content of the surface layer. The product is placed in a refrigerating chamber, air is supplied with a negative temperature and is cooled to a temperature below the cryoscopic one. When the product reaches the surface temperature equal to the processing air temperature, the latter is moistened to supersaturation and is affected by this supersaturated cooling air until the product reaches a mass equal to its mass when cooled to a cryoscopic temperature. 2 Il. (L

Description

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The invention relates to refrigeration engineering, in particular to methods of air freezing products, mainly meat.

The aim of the invention is to reduce the mass loss of the product during the freezing process by restoring the moisture content of the surface layer.

The method is carried out as follows.

The product is placed in a refrigerating chamber, air is supplied at a negative temperature and is cooled to a temperature below the cryoscopic one. When the product reaches the surface of the product, the temperature is equal to the temperature of the processing air, the latter is moistened to the state of supersaturation and influenced by this peresischenny cooling air until the product reaches a mass equal to it when cooled to the cryoscopic temperature.

If the surface of the product is below the temperature of supersaturated air, there is an intense loss of moisture on the product that prevents the moisture from being absorbed by the dehydrated layer. If the temperature of the product is higher than the temperature of the perennial air, the absorption of moisture by the surface layer of the product does not occur, since the partial pressure of water vapor in the suspended air is lower than the partial pressure of water vapor on the product surface.

The frozen product absorbs not all of the moisture lost as a result of shrinkage from underperformed air, but only that part that evaporated after reaching the product's surface at a cryoscopic temperature. Therefore, after increasing the mass of the product to a value equal to the mass of the product its surface is cryoscopic, air humidification ceases

Fig. 1 shows the devices for implementing the proposed method j in Fig. 2, a graph of the dependence of the weight of the drug (increase in drying) on the surface temperature during the heat treatment,

The device contains a chamber 1, a steam generator 2, a fan 3 and under

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weight paths 4, on which the processed product 5 is placed.

The method is carried out as follows.

The product 5 is placed in the chamber 1, the air from the refrigerating chamber - with a temperature of minus 22 ° C using the fan 3 is fed into the chamber 1 directly after reducing the temperature of the product surface to minus, water vapor is added to the air stream supplied by the fan 3 produced by the steam generator 2. In this case, the air is supersaturated with moisture, and its temperature rises and becomes equal to minus. Product 5, washed by supersaturated air having a temperature equal to the temperature of the product surface, absorbs part of the moisture from ozduha.

M of the first category are frozen at the air temperature in the chamber minus 22 ° С (line 3). The nature of the change in product temperature is determined by the line 2, with shrinkage. product increases (line 1). Moreover, at the site of the drying process occurs under conditions when a frozen layer forms on the surface of the product and moisture is filtered to the surface of the product, therefore, the dehydration of the surface layer occurs,

After the temperature of the product has decreased to minus 21 ° C, the air in the chamber is moistened, for example, with steam and air is supersaturated with moisture. The wetting period is 24 hours and is equal to half the freezing period (FIG. 2, the gritted area 4). At the same time, the air temperature slightly rises and becomes equal to the temperature of the product surface (line 3),

During the specified period of time, the moisture content of the surface layer of the product (area ed) is restored, and not all of the moisture lost by the product is recovered, but only that part that sublimated after the cryoscopic temperature was reached on the surface of the product, the IJTO all shrinkage.

During subsequent transportation and storage, shrinkage of the frozen product occurs due to moisture;

polished surface layer of the product, which prevents further drying and reduces the weight loss of the product.

Freezing the product with the proposed method can be carried out; However, in a chamber without a humidification system, but immediately after the surface of the product reaches a temperature equal to the cooling air temperature, the latter should be placed in another room with a humidification system, and the air in it should be humidified to overdose.

The proposed method allows to reduce the natural mass loss of the product during heat treatment by 35-40%

The economic efficiency of the invention is achieved by reducing the natural loss of the product by 35% (capital costs are about the same).

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Claims (1)

Claims method of freezing foodstuffs, including placing them in the refrigerating chamber, air supply with a negative temperature, cooling to a temperature below the cryoscopic, exposure to cooling air, humidified to Transfer, characterized in that in order to reduce the mass flow of the product in the process of freezing due to the restoration of the moisture content of the surface layer, air when the surface of the product reaches the surface the temperature is equal to the temperature of the processing air and is affected by this supersaturated cooling air to reach the product mass equal to its mass when cooled to a cryoscopic temperature. 1 Ls.kg gd 49 IS 20 J) zif z / Ch. eight 7Z 2