Heat-mass transfer in layer of berries during freezing process

Abstract

Qualitative changes of berries during freezing have been investigated with instrumental methods. In order to economize energy it is proposed to determine the freezing temperature of products. The objective characterisation of physical properties of products enabled to evaluate the quality, to incorporate it into the technological regimes of the treatment. Numerical results of process modelling are shown. The freezing regime is defined by several thermo-physical parameters of the production. Water stage turning into ice essentially affects the quality of the frozen product. In products ice crystal formation takes place at a relatively low temperature. This susceptibility of sugar containing products to temperature fluctuations possibly is due to their high concentrations of unfrozen water and lower melting temperature. It is possible to calculate the mass fraction of ice depending on the temperature and moisture content in product what is very important for predicting the product quality. Experimental investigation was carried out at the Institute of Horticulture, Latvia University of Agriculture.