低温诱导羊乳中β-酪蛋白从胶束中解离的研究

Dissociation of β-Casein from Casein Micelles in Skimmed Goat Milk at Low Temperature

摘要:

在羊乳酪蛋白胶束结构中，部分β-酪蛋白通过疏水作用结合到胶束骨架上，在低温条件下，蛋白质疏水作用减弱，部分β-酪蛋白从胶束中解离。以脱脂羊乳为原料，采用HPLC、SDS -PAGE、ICP-MS进行检测，研究温度、平衡时间、pH、NaCl、柠檬酸钠、CaCl2对β-酪蛋白从胶束中解离的影响。低温诱导β-酪蛋白从胶束中的解离在120 min达到平衡。降低温度、降低pH、添加柠檬酸钠诱导胶束钙的解离，使胶束中通过疏水作用结合的β-酪蛋白含量增加，进一步促使低温条件下β-酪蛋白从胶束中解离。温度4 ℃、pH 6.0条件下平衡120 min，β-酪蛋白从胶束中的选择性解离效果较好，β-酪蛋白、κ-酪蛋白、α-酪蛋白的解离率分别达41.8%、19.9%、15.2%，3种酪蛋白解离部分的占比分别为68.2%、24.4%、7.4%。上述结果可应用于羊乳β-酪蛋白低温微滤分离的工艺优化。

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.