摘要:
采用圆二色谱(CD)、荧光分光光度计、扫描电子显微镜(SEM)、纳米粒度仪对巴氏杀菌与超高温灭菌（UHT）牛乳酪蛋白的二级结构、内源荧光发射光谱、胶束形态结构、粒径分布情况进行研究.结果表明,相对于巴氏杀菌牛乳酪蛋白（α-螺旋47.4%、β-折叠19.7%、β-转角13.4%、无规卷曲19.4%）,UHT牛乳酪蛋白的无规则结构增多（α-螺旋22.1%、β-折叠23.1%、β-转角22.4%、无规卷曲33.4%）；UHT牛乳酪蛋白色氨酸在酪蛋白中所处的环境疏水性增强；巴氏杀菌牛乳酪蛋白颗粒呈圆球状,表面光滑,能够连接成较短的胶束结构,而UHT牛乳酪蛋白表面不光滑,几乎不能形成胶束；巴氏杀菌牛乳酪蛋白平均粒径为295.1 nm,UHT乳酪蛋白平均颗粒明显变小,平均粒径为221.7 nm.可见,巴氏杀菌乳与超高温灭菌乳之间存在明显的结构差异.
关键词:
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巴氏杀菌
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超高温灭菌
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酪蛋白
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结构
Abstract:
Secondary structure, intrinsic fluorescence emission spectra, micelle morphology and particle size distribution of bovine casein were researched respectively by circular dichroism, fluorescence spectrophotometer, scanning electron microscope and nano-particle size analyzer. Results showed that bovine casein by ultrahigh temperature sterilization (UHT) had more random structures(α-helix 22.1%, β-sheet 23.1%, β-turn 22.4%, random 33.4%), compared with casein by pasteurization(α-helix 47.4%, β-sheet 19.7%, β-turn 13.4%, random 19.4%). Tryptophan of casein by UHT had more hydrophobic. Casein particles by pasteurization were spherical with smooth surface, and able to connect to short micelles. But casein particle by UHT did not have smooth surface, and could not connect to micelles. Compared with pasteurization, casein particles by UHT was smaller, with the diameter being 221.7 nm. This research suggested the structure of casein by pasteurization and ultrahigh temperature sterilization had obvious differences.
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