Effects of cycled high pressure treatment on casein micelles and whey proteins in bovine milk

Dividing a high pressure (HP) treatment at 250 MPa into multiple cycles, without delay between cycles, resulted in a greater increase in casein micelle size, less denaturation of β-lactoglobulin (β-lg) and less β-lg associated with the casein micelles, than a similar total duration of treatment applied in one cycle. Dividing a treatment at 250 MPa into 2 cycles, with a 4 h interval between cycles, also increased casein micelle size considerably, compared to a treatment of similar total duration applied in one cycle, but had little effect on the level of denatured β-lg and resulted in less β-lg associated with the casein micelles. The poor correlation between increases in micelle size and the level of β-lg associated with the casein micelles on cycled HP treatment at 250 MPa suggests that these increases in micelle size are not due to interactions with β-lg, but possibly to the formation of large casein aggregates. Treatment at 400 MPa reduced casein micelle size; dividing a HP treatment at 400 MPa into a number of shorter cycles, with or without delay between cycles, had little further effect on micelle size or denaturation of β-lg, indicating that micellar particles formed at this pressure are stable end-products.