Abstract:Within goat casein micelles, part of β-casein is bound to the micelle skeleton through hydrophobic interaction. The protein hydrophobic bonds are weakened at low temperature,contributing to the dissociation of β-casein from the micelles. Goat skim milk was used in this study, and the effects of temperature, equilibration time, pH and the addition of NaCl, sodium citrate and CaCl2 on the dissociation of ββ-casein from casein micelles were investigated, based on the indicators such as HPLC, SDS-PAGE and ICP-MS. The results showed that low-temperature induced the dissociation of β-casein from micelles, reaching an equilibrium state at 120 min. The reduction in temperature and pH, as well as the addition of sodium citrate induced the dissociation of colloidal calcium, also increasing the proportion of β-casein bound by hydrophobic bonds within the micelles, thus further promoting the dissociation of β-casein from the micelles at low temperature. The optimal selective dissociation of β-casein from micelles was achieved after 120 min of incubation at 4 ℃ and pH 6.0. The dissociation rate of β-casein, κ-casein and α-casein reached 41.8%, 19.9% and 15.2%, with the proportions of the dissociated parts of the three caseins being 68.2%, 24.4% and 7.4%, respectively. The above results can be applied in process optimization of cold microfiltration for the goat β-casein fractionation.
