Thermomechanical actions effect on the composition and antioxidant activity of milk

The aim of the study is to determine changes in the composition and antioxidant activity (AOA) of native milk during homogenization at minimal temperature exposure. Objects of research are raw milk obtained from an individual farm in the Moscow Region, and bulk raw milk supplied to the industry enterprise; homogenized milk. Homogenization was carried out on a laboratory setup in the pressure range of 12.5-21 MPa at temperature conditions of 28-30 and 38-40 °C. Antioxidant activity (total content of water-soluble antioxidants) was determined by the amperometric method using a “CVET YAUZA-01-AA” spectrometer. Integral antioxidant activity was determined using an “Expert-006” coulometer at the Moscow State University of Food Production. Physicochemical parameters of milk were determined by standardized methods. Oxidation-reduction potential (ORP) and active acidity were determined using a pH-meter ionomer "Expert-001". As a result of the study, it was found that: thermomechanical action on milk at a homogenization pressure of 12.5-21.0 MPa and a temperature of 38-40 °C leads to changes in titratable and active acidity, redox potential, protein mass fraction, calcium mass fraction; freezing milk at a temperature of minus 16-20 °C and storing it before homogenization for 10-40 days in a freezer does not affect the content of water-soluble antioxidants in the original native (samples No. 2, 4); homogenization of pre-frozen milk (10 days of storage in a freezer) at a temperature of 38-40 °C and a pressure of 12.5-21 MPa increases its AOA (samples 2, 3); an increase in the duration of storage of frozen milk up to 40 days and subsequent homogenization at a temperature of 28-30 °C do not affect the antioxidant activity (sample No. 4). Based on the data obtained, it can be concluded that prolonged exposure to negative temperatures on milk leads to a presumptive inactivation of the xanthine oxidase enzyme and a slowdown in redox processes.