Physical, chemical and microbiological changes in liquid micellar casein concentrates induced by high-pressure treatments

Microfiltration and diafiltration were conducted to obtain 3 distinct levels of liquid micellar casein concentrates from raw skim milk: 8, 10 and 11.5 g casein/100 g. All the concentrates were subjected to 300, 450 and 600 MPa for 5 min. The physicochemical and microbiological changes in the matrix were studied and compared with their untreated counterparts on the day of production and after storing the samples for 7 d at 10 °C. Slight changes in pH were correlated with pressurization; the higher the pressure the greater the decrease in pH. For the least concentrated sample, changes were more noticeable. Furthermore, changes in particle size mainly occurred as a consequence of pressurization but also depended on casein concentration: aggregation and disruption phenomena were observed in the most concentrated samples. In terms of microbial quality, 600 MPa was the only treatment capable of achieving effective microbial control.