Effect of thermosonication process on physicochemical properties and microbial load of goat's milk.

Abstract

In this study, thermosonication was used as a combined treatment of raw goat milk (RGM) using pasteurization (72°C for 15s) and ultrasound treatments (20kHz at the power variance of 150W, 200W, 300W and 400W for 10min). Investigation on the impact of the microbial load, protein content, protein aggregation, the particle size of fat and casein micelles, pH, viscosity, turbidity, color, and soluble calcium and phosphorus contents were carried out, whiles RGM and PGM served as the control. Our results revealed that at 400W, that thermosonication resulted in a significant reduction (α = 0.05) in the microbial load of the samples to less than 2.3 log cfu/mL in comparison to those of RGM and pasteurized goat milk (PGM) at 5.94 log cfu/mL and 4.76 log cfu/mL respectively. In RGM, the fat size (3.5µm) decreased to 0.4µm at 300W; while those of casein micelles also decreased from 406 to 256.4nm at 400W. However, no significant effect was observed in the color and soluble calcium and phosphorus contents of all samples. The effect on the microbial load and fat homogenization would promote thermosonication process in the dairy industry.