THE CHANGE OF THERMAL AND PHYSICAL CHARACTERISTICS OF SEA BUCKTHORN BERRIES DURING FREEZING

Abstract

Sea buckthorn berries occupy important place in the diet of the inhabitants of Siberia. They are the richest source of vitamins C and E, contain significant amounts of carotenoids, various vitamins of B, F, P groups, minerals, and contribute to the maintenance of health and longevity. One of the most effective methods of preserving fruits and berries is freezing. To develop efficient and energy-saving technology of low temperature preservation and storage of fruits and berries, particularly berries of sea buckthorn, we need reliable and objective information about their thermal and physical characteristics over the entire range of temperature exposure. In addition, knowledge of the thermal and physical characteristics is necessary for designing and selecting the process equipment to implement the freezing processes. This article is devoted to investigations of thermal and physicals characteristics of buckthorn berries of different varieties in fresh and frozen conditions. The first buffer method of two temperature-time intervals has been selected for determination of thermal and physicals characteristics. The methodology of the experiment and data processing method for determining the thermal properties of buckthorn berries at temperatures above cryoscopic point and after freezing have been described. The measured values of thermal and physical characteristics of five buckthorn berry varieties in fresh and frozen conditions are given. It has been established that the values of thermal and physical characteristics of the berries are determined to the greatest extent by their moisture mass fraction. Fluctuations in the values of thermal and physical characteristics of different varieties of sea buckthorn berries are very small, therefore, average values of thermal and physical characteristics should be used for heat engineering calculations of technological processes connected with thermal effects.

Keywords

• thermal and physical characteristics
• buckthorn berries
• thermal conductivity
• thermal diffusivity
• heat capacity