热处理对酸马奶中蛋白质稳定性的影响

Effects of Thermal Treatments on the Protein Stability of Koumiss

为弄清热处理对酸马奶再加热蛋白质稳定性的影响,测定不同热处理的酸马奶的相关指标,并结合SDS-PAGE图谱分析酸马奶蛋白质的悬浮稳定性和乳清蛋白变性程度,用傅里叶变换红外光谱技术对其二级结构进行表征。结果表明:65℃至90℃的热处理对酸马奶的酸度和pH值无显著影响,与未热处理相比,热处理的酸马奶蛋白质的离心悬浮量、变性率和二级结构比例发生显著变化(P<0.05)。β-折叠比例的变化对酸马奶蛋白质热聚集体聚集程度具有重要影响;随着热处理程度的增强,酸马奶黏度和乳清蛋白变性程度不断增大,变性率分别为38.52%,40.88%,50.94%,69.03%,呈加速增大的趋势。90℃/5 min热处理后β-乳球蛋白基本消失,严重破坏了乳清蛋白的稳定性,ζ-电位、蛋白质悬浮稳定性和β-折叠比例均呈先增后降的趋势。结论:适当的热处理能提高酸马奶蛋白质的稳定性。

The objective of this study was to explore and compare the effect of different thermal treatments on the stability of koumiss proteins.It measured indicators of koumiss quality at different heat treatment conditions,and then the suspension stability of koumiss protein as well as the denaturation degree of whey protein were observed by SDS-PAGE.Fourier transform infrared spectroscopy was employed to investigate the variation of secondary structures.The results showed that thermal treatment from 65℃to 90℃had no effect on the acidity and pH value of koumiss,but the centrifugal suspension content,denaturation rate and the proportion of secondary structures of koumiss protein after heat treatment changed significantly compared with those without heat treatment(P<0.05).The variation ofβ-sheet played an important role in the degree of thermal aggregate of koumiss protein.With the increase of the degree of thermal treatment,the viscosity of koumiss and the degree of denaturation of whey protein increased continuously,and the denaturation rates were 38.52%,40.88%,50.94%and 69.03%respectively,which showed an accelerated increasing trend.After heat treatment at 90℃for 5 minβ-Lactoglobulin disappeared and the stability of whey protein was seriously damaged.Moreover,the properties of zeta-potential,protein suspension stability andβ-sheet structure showed a trend that increased firstly and then decreased.Appropriate thermal treatment could improve the stability of koumiss proteins.