Investigations of the dynamics of meat freezing at various modes of cryotreatment.

The paper presents the results of an experimental investigation of the dynamics of freezing meat products samples at different modes of low-temperature treatment. The measurements were performed using a system of thermocouples which is inserted into the sample at a fixed distance as among them, and relatively a surface of the investigated sample which allow getting a 2D temperature distribution. Temperature measurements were carried out using a temperature controller TC 325 (Lake Shore). Investigations were conducted in two modes of cryotreatment. In the first experiment the sample is plunged directly in the liquid nitrogen, and the temperature distribution over the sample volume was measured. In the second case, cryotreatment was performed in a specially designed measuring cell, allowing except for dynamic researches to measure the thermal conductivity of the meat samples. Thus, in the second case, cooling was performed during mechanical and thermal contact of the sample with the cooled substrate. During the measurements it was shown that the process of freezing the samples has nonlinear time dependence with a characteristic minimum at a particular temperature. It is assumed that this is due to the change in the value of coefficient of the thermal conductivity of the sample during the movement of the crystallization front in the cooling process.