WAY of HIGH-QUALITY DRYING

LIQUID FOOD

Kaziev M., Dauletov M., Kaldibaev A.

South Kazakhstan State University named after M. Auezov, Kazakhstan

One way of solving the problem of supplying the population of Kazakhstan with high-quality vitamins, irrespective of distance and seasonal conditions, concerns drying or condensation of liquid food such as milk, dairy drinks (kumis, shoobut), fruit and vegetable juices.

The main problem of canning products in this way is the difficulty of preserving the valuable components that comprise their biological and flavouring value: the vitamins and substances that give a product its specific taste, aroma and colour.

The above named products are widely used in the industry because the high temperature of the process does not allow for high-quality tinned products.

The development of freeze drying [1] solves the problem of the quality of the products. However, because of the complexity of installation and the high cost of tinned products, this way has not found wide application in the industry.

In the given work the new method of low-temperature drying of liquid food is given [2]. The design of a dryer, in which the offered way is realized, is submitted in figure 1.

It consists of the following basic elements: 1 - drying chamber; 2 - site for a SHF (Super High Frequency) heating field; 3 – an atomizer; 4 - radiating source; 5 - chamber for gathering of a complete product, whose quantity is limited by corks at the input and output maneuvered by cranes; 6 – shell and tube for the condenser; 7 - vacuum pump; 8 - refrigeration machine; 9 – high-lift pump.

The installation works as follows. Liquid food under pressure of 6-12 atmospheres, by the pump (9) moves to site 2, where in the field of the SHF is quickly (in 2 minutes) heated up. For example, for drying of milk or juices the temperature reaches 80-110⁰С. On the site, instant pasteurization of a product occurs. Further pasteurization of the product occurs in the atomizer (3) and spraying in the drying chamber 1, where the vacuum with residual pressure 0,01 kgsec/centimeter² (kiloPa) is supported. The presence of a sharp fall of pressure during spraying results in the effect of explosive boiling. As a result 30-40 % of the moisture evaporates at once at the moment of sprinkling. The remaining drops of the sprayed product at high speed are dumped into the drying chamber. The space irradiated (sourced) by radiator (4) is located on the internal surface of the walls of the drying chamber. The infrared rays transmit heat many times more quickly than direct-heat drying. Therefore the drops quickly dehydrate (during 1,5 ÷ 2 seconds).

Figure 1 – The vacuum radiating installation for drying or

condensation liquid food

The powder forms when a dried product settles on the bottom of the drying chamber, where it is poured into cone-shape drains leading the chamber to the finished product (5). After the first container is filled, the top cork is sealed by a crane, and the cork on the second chamber is removed. In it a vacuum equal to the vacuum in the drying chamber is supported. In the first chamber a vacuum is created while the second chamber is filled by use of superfluous pressure from Nitrogen Cylinder. After that the bottom cork opens by crane and the dry product is squeezed out by nitrogen from the chamber for packing. After emptying the chamber the bottom cork is closed by crane and in it the additional vacuum pump creates a vacuum equal to the vacuum in the drying chamber.

From this moment the chamber is ready to connect to a dryer, and after filling the second chamber the resulting dried product will go through. Thus, the chambers for the ready product work serially. Formed at drying, low-temperature steam flows countercurrent (back shot) to the sprayed drops and drawn off from the drying chamber by the vacuum pump (7). Passing through the condenser (6), they are cooled and condensed, and contained in steam not condensed (fixed), gases are removed from the environment by the vacuum pump.

Distilled water moves through the tubes of the condenser which cools down to 0-20⁰С in the refrigerating machine.

One of the positive aspects of the developed installation is that in it the pasteurization process goes simultaneously with the process to concentrate or dry a liquid product. Besides, the process of cooling pasteurization of a product goes very quickly at the expense of using of phase transition at wire-drawing of the heated product in a vacuum. At throttling there is an explosive boiling and at the expense of evaporation of a part of a liquid the product is quickly cooled from 100⁰С down to 8⁰С. Due to the process of fast cooling valuable components of the product will not have time to collapse. As a result we will receive high-quality final concentrated or dry products with preservation of all valuable components of the initial natural product.

To test the developed dryer and define its optimum regiment working parameters, we plan to manufacture functional installation producing 60 liter/hour from initial liquid solution - milk, juice.

THE LITERATURE

1. Kamovnikov B.P. Etc. Vacuum – freeze drying of food. - M.: 1985 - 196с.

2. Fore-patent of RK. № 18762. Way and device for drying and condensation of liquid solutions // Kaziev М.Т. Published in 17.09.2007., bulletin № 9.