Effect of high pressure treatment on selected properties of the milk emulsion phase

In this study, the effect of high pressure treatment in the range of 200-1000 MPa (t(const) = 15 min, T-const = 20 degrees C), increasing by 200 MPa and varying in exposure time of 15, 25, 35 min (P-const = 800 MPa, T-const = 20 degrees C) on selected properties of emulsifying and colloidal phases of milk with 3.5% fat content was examined. The diameter of fat globules in milk increased, which was accompanied by a decrease in the area of the milk fat along with increased pressure and prolonged exposure time. An approximately 25% increase in the Sauter diameter of fat globules in milk (indicating their size diversity) was especially explicit at >= 800 MPa (statistically significant at alpha < 0.01). The aggregation and deformation of fat globules in milk exposed to high pressure treatment was also observed. The application of high pressure almost doubled the content of milk plasma proteins associated with the surface of fat globules, and the tendency of changes was more noticeable along with increasing pressure and exposure time (statistically significant differences at alpha < 0.01). The amount of proteins remaining in milk plasma (both coagulating and soluble at pH 4.6) was decreased, while their ratio reached 4.9 in the case of the control sample and increased along with higher pressure (max. 8.6) and prolonged exposure time (max. 9.3).