SU1374009A1 - Method of sublimation drying of concentrated liquid food products - Google Patents

Abstract

The invention relates to the freeze drying of concentrated liquid food products. The aim of the invention is to reduce energy consumption. Before heating in vacuum, the open surface of the frozen product is glazed with a thin layer of pure water ice. 1 tab.

Description

00

kt

eleven

The invention relates to the drying of food products, in particular to the drying of concentrated liquids by sublimation.

The aim of the invention is to reduce energy costs.

The method consists in the fact that the layer of ice glaze produces a partial dilution and freezing of the highly concentrated layer on the surface, and the water activity in this layer is slightly different from 1. By glazing, the vapor permeability of the highly concentrated layer is improved without reducing thermal conductivity of the main layer of the concentrated product in vacuum.

The proposed method carried out freeze-drying of the following concentrated liquid products: beet juice, milk, block puree, apricot puree with 40% sugar content.

The concentrated liquid product is poured into trays in a thin layer, frozen and water is introduced into the layer, enrobing its open surface with pure ice, then placed in a sublimation chamber and dried.

The method is illustrated with specific examples.

Example 1. Take beet juice, sks centered to 40%, razamora

poured into trays in a thin layer, live at -30 ° C, the surface of the product is glazed with pure ice 1 mm thick, then the product is placed in a sublimation chamber, where it is heated under a residual pressure of 0.5 mm Hg. according to the method of extreme temperatures: upper extreme temperature + 55 ° С lower extreme temperature. The drying time to a final moisture content of 5% is .440 minutes. The specific installation capacity per unit area of the tray is 0.341. The specific energy consumption for heating is 7.21 kWh / kg.

Example 2. Milk is taken at a concentration of 45%, poured into trays and frozen at -30 ° C, then the surface of the product is glazed with pure ice 1 mm thick, the product is placed in a sublimator, where

subjected to heating at a residual pressure of 0.5 mm Hg. according to the method of extreme temperatures: the upper extreme temperature is + 55 ° C, the lower extreme temperature is 20 C. The drying time to a final moisture content of 5% is 360 minutes, and the specific unit capacity per unit of tray area is 0.512 kg / MH. Specific energy consumption for heating is 6.43 kWh / cGo

The results of the examples are shown in the table in comparison with the drying of the prototype.

0

five

0

Prototype

The proposed method:

Example 1

Example 2

450

0.197

22.35

440360

0.341 0.512

7.2 6.43

Thus, as can be seen from the table, for the same product with the same duration of sa, the specific energy consumption for heating is reduced by 15.44 kWh / kg, and the specific productivity per unit area of the tray increases by 0.144 kg / mh.

Claims (1)

Invention Formula The method of freeze-drying of concentrated liquid food products, including the introduction of water into the product, pouring into trays in a thin layer, freezing and subsequent heating 313740094 the product under vacuum, about tl and h a-, is produced before heating by means of si ni and so that, in order to reduce energy consumption on the open surface, the introduction of water from the product of ice glaze.