该文研究了鲜羊乳经过不同热杀菌处理后的聚集行为及蛋白质结构变化。随着处理温度的增加,羊乳酪蛋白胶束平均粒径从209.6 nm增大到289.2 nm,粒径分布峰宽变大,经121 ℃/4 s超高温处理后粒径增加显著,乳清蛋白发生变性,并在蛋白胶束表面聚集,使蛋白胶束增大。傅里叶红外光谱扫描结果显示,经热处理后羊乳的吸收峰均发生一定程度的红移,蛋白分子氢键发生断裂与重新缔合,通过酰胺Ⅰ带和酰胺Ⅲ带分析乳中蛋白的二级构象变化,发现无规则卷曲含量显著增高,疏水区域外翻,羊乳蛋白的空间结构发生变化。变性聚丙烯酰胺凝胶电泳分析表明,β-乳球蛋白在酪蛋白与清蛋白结合中发挥重要作用。该研究探讨了不同热杀菌方式乳稳定性及蛋白结构的变化,以期为液态羊乳生产中热杀菌方式对蛋白质的影响提供理论参考。
The aggregation of raw goat milk under the different heat sterilization treatments was investigated based on protein structure and interaction. With the increasing heating temperature, the average particle size of goat casein micelles increased from 209.6 nm to 289.2 nm, and the range of particle size distribution increased as well. Under the ultra-high temperature treatment at 121 ℃ for 4 s, the particle size significantly enlarged due to the denaturation and aggregation of whey protein on the surface of casein micelles. Fourier infrared chromatographic scanning results showed that heat treatment conditions could result in a red shift of absorption peaks of goat milk to lower wavenumbers, suggesting that the hydrogen bonds of protein molecules were broken and re-associated. The secondary conformation of milk proteins was analyzed by amide I and amide III. The content of coils was significantly increased and the hydrophobic regions were turned out, causing changes in the spatial structure of goat milk protein. β-lactoglobulin played an important role in the binding of casein micelles with other whey proteins evidenced by SDS-PAGE gel electrophoresis analysis. This study investigated the changes in milk stability and protein structure by different heat sterilization methods to provide a theoretical reference for the effect of heat sterilization methods on protein in liquid goat milk production.
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