Heat and/or high-pressure treatment of skim milk: changes to the casein micelle size, whey proteins and the acid gelation properties of the milk

Skim milk was subjected to heat, pressure or combined processes. In general, higher levels of whey protein denaturation were observed for milk subjected to combined processes than those heat- or pressure-treated only. Heat treatment caused small changes to the casein micelle size. Pressure treatment decreased the casein micelle size; however, the effect was less marked when heat and pressure treatments were combined. Acidification of the skim milks produced gels with a range of firmness, yield stresses and yield strains depending on the treatments applied. These changes in acid gel properties were not related only to whey protein denaturation levels in the milks.