SU1155231A1 - Method of obtaining concentrated liquid food products - Google Patents

Abstract

A METHOD FOR OBTAINING CONCENTRATED LIQUID FOOD PRODUCTS, which involves freezing water on a cooling surface before the formation of ice, characterized in that, in order to reduce the loss of dry substances, the process of freezing ice alternates with the process of defrosting the top layer of ice to ensure alternation of crystallization of ice and melting ice ice blocks. phase separation. With 8 JV SL IN9 with

Description

The invention relates to refrigeration technology, in particular to methods for the cryoconcentration of liquid food products.

Methods are known for the preparation of concentrated liquid food products by freezing a portion of the water, allowing sufficiently to keep the thermolabile and volatile components of these products 1.

The lack of these methods consists in a significant content of dry substances in the formed ice due to the penetration of the microparticles of the concentrate into its intercrystalline voids, as well as in the insufficient intensity of the concentration process.

The closest to the proposed technical essence and the achieved result is a method of obtaining concentrated liquid food products, which involves freezing water on the cooling surface before the formation of ice 2.

However, this method does not prevent the relatively high loss of dry substances with ice caused by the capture of the concentrate into the space between the crystals of the ice lattice, which is frozen on the heat sink surface. In addition, it is necessary to observe the minimum rate of movement of the ice-solution interface, which reduces the intensity of the process of concentration of the liquid product.

The purpose of the invention is to reduce the loss of solids during the concentration of liquid solutions of food products.

The goal is achieved in that according to the method of obtaining concentrated liquid food products, which involves freezing water on the cooling surface before ice is formed, the process of ice freezing alternates with the process of defrosting the upper ice layer to ensure alternation of water crystallization and ice melting at the interface.

The drawing shows a scheme for freezing water from a solution onto a cooling surface (a) and melting ice at the interface in accordance with the proposed method (b).

At the crystallization stage, small ice crystals grow, while the Ci concentration of solution 2 at the phase boundary increases by .ct.Cj and, consequently, as the ice layer accumulates, the solids content in it increases. Then, at the stage of melting, ice 1 with a high content of solids is first melted, namely, small crystals, and medium and large ones just begin to melt. Since the concentration of dry substances in ice is much lower than in solution, at the phase interface it decreases sharply by d C.

The latter circumstance makes it possible, during recrystallization, to obtain medium and large ice crystals with a low content of solids in this layer. The next layer of ice is already frozen under the conditions described, therefore it is necessary to repeat the melting step for it.

Consequently, the sequence of stages of crystallization and melting, wire process

cryoconcentration in the oscillating mode of the product temperature can significantly reduce product loss with ice.

Example. The beet juice is cryoconcentrated with an initial concentration of 12%, which is cooled to a temperature of - 2 ° C. Then, a layer of ice 4 mm thick is frozen on the heat sink surface, the temperature of the juice is then raised to –4 ° C, the ice layer melts to a depth of 2 mm, then another 4 mm of ice is frozen to a total thickness of 6 mm, then the temperature is increased the juice reaches –4 ° С and melts 2 mm of ice, then ice is frozen up to 8 mm, then the layer is melted up to 6 rlm and frozen by 10 mm, melted up to 8 mm,

5 are frozen to 12 mm, melted to 10 mm. At the end of the process, 22.5 ° / oh of beet juice concentrate is poured and ice is melted with a solids concentration of 2.5%.

For comparison, beet juice with an initial concentration of 12 / o is cooled to

 temperatures of -2 ° C, then at the cryoscopic temperature of the juice, a layer of ice 10 mm thick is frozen on the heat-removing surface, at the end of the process 17.5% beet juice concentrate is drained and ice is melted with a dry matter concentration of 6.5%.

Data for comparison of the methods are tabulated.

As can be seen from the table, the application of the proposed method of cryoconcentration

0 allows to reduce the loss of dry substances with ice, which in turn intensifies the process of concentration.

Using the proposed method for cryoconcentration of liquid food products in an oscillating solution temperature mode does not require additional equipment as compared with the prototype and provides a drastic decrease in the solids content in ice, which is especially important when concentrating expensive products, increasing the concentrate yield per unit area of heat sink surface , which significantly reduces the share of capital expenditures in the cost of the final product, reducing the requirements for accuracy the temperature of the heat-removing surface, which makes it possible to refuse the brine cooling system and shorten the duration of the concentration process.

Cryoconcentration at cryoscopic product temperature (prototype)

With oscillating product temperature mode (suggested)

6.5

17.5

22.5

2.5

Claims (1)

METHOD FOR PRODUCING HONCENTRATED LIQUID FOOD PRODUCTS, which involves freezing water on a cooling surface until ice forms, characterized in that, in order to reduce the loss of dry substances, the process of ice freezing is alternated with the process of thawing the upper ice layer to ensure alternation of water crystallization and ice melting at the interface phases. X