The effect of freezing rate, frozen storage time and thawing methods on the concentration of thymosin proteins in pork meat

Abstract

Proteins are the most important ingredients in meat. They are found in meat in different forms and with different functions. Thymosins are small proteins present in many animal tissues, with molecular weights of 1000–15000 Da. The technological processing of meat causes changes in the amount and shape of the basic ingredients. During the freezing of meat and its storage in the frozen state, various chemical reactions take place causing changes in the proteins. The aim of this paper was to examine the influence of the freezing rate and thawing methods on the changes and behaviour of thymosin proteins in pork meat (M. longissimus thoracis et lumborum) during storage. Protein analyses were performed using capillary gel electrophoresis (CGE) and the SDS-MW Analysis Kit (Beckman Coulter). The meat samples were frozen at 10 different rates (from 0.23 cm/h to 1.43 cm/h). The samples were tested at different times during 60 days of storage at -20oC (after 1, 15, 30, 45, 60 days). Before the analysis, the samples were thawed in the refrigerator, at room temperature and in the microwave. After one day of storing frozen meat samples, the relative concentration of thymosin was less than 1% in all tested samples. During 60 days of storage, most samples had a slight increase in the relative concentration of thymosin. The highest relative concentration of thymosin after 60 days of storage (1.67%) was recorded in a meat sample that was frozen at a rate of 1.10 cm/h and thawed in a microwave oven.