Lipid peroxidation and milk heat treatment to prepare fermented milk product of mixed fermentation

The purpose of research is to study the effect of thermal exposure on the processes of lipid peroxidation in milk intended for obtaining a fermented milk product of long-term mixed fermentation, and to determine the pasteurization temperature of the mixture. Tasks: determination of lipid oxidation indices in heat-treated milk when initiating free-radical oxidation and efficiency of pasteurization of raw materials. The objects of research are raw, thermized, pasteurized and ultra-pasteurized milk. To determine the products of lipid oxidation in the studied milk during the initiation of oxidation processes, an extraction-spectrophotometric method was used with the registration of lipid peroxides in the heptane and isopropanol phases. Registration of oxidation products was carried out using a spectrophotometer. The results obtained were expressed in terms of oxidation indices. The experiments carried out made it possible to establish that the content of primary and secondary products of lipid peroxidation in milk grows with an increase in the modes of its heat treatment. The highest values of lipid oxidation indices were obtained in UHT milk with a pasteurization temperature of 137 °C. The oxidation indices of the final oxidation products are inversely related to the pasteurization temperature. The optimal pasteurization temperature was chosen to obtain a fermented milk product of mixed fermentation, which allows maintaining sufficiently high microbiological safety indicators and, at the same time, a lower level of lipid oxidation under the influence of heat treatment (90-95 °C with a holding time of 3 min). The conducted studies show the potential use of lipid markers for the development of methods for thermal treatment of milk, which minimize the modification of fats and retain their inherent functionality and nutritional properties, which has a positive effect on the finished product with a long period of fermentation and maturation.