Changes in some quality properties of frozen mare milk during 6 months of storage

Abstract

The aim of this study was to determine how storage in the frozen state affects the quality of mare milk. Therefore, physicochemical properties such as pH, total dissolved solids (TDS), electrical conductivity (EC), particle size distribution and near-infrared (NIR) spectroscopy, as well as changes in antioxidant activity and the total phenol content were determined during 6 months of storage at -18°C. All of the determined parameters were compared to those in raw mare milk prior to freezing. According to the obtained results, frozen storage caused certain changes in mare milk quality, including increase in pH, electrical conductivity and TDS values, changes in protein structure recorded by NIR spectroscopy and SDS PAGE (Sodium dodecyl sulfate-polyacrylamide gel electrophoresis), as well as changes in particle size distribution. There was also a continuous decrease in the antioxidant activity and the total phenol content of frozen mare milk throughout the 6 months of frozen storage. Thus, after 6 months of frozen storage, a decrease in the DPPH value of approximately 59%, in the FRAP value of approximately 26% and in the TPC of approximately 70% was observed, respectively. In conclusion, freezing and frozen storage affected the quality of mare milk, which might have negative consequences on its therapeutic value.