Advanced Food Systems Research Unit, Institute for Sustainable Industries & Liveable Cities, College of Health and Biomedicine, Victoria University, Melbourne, VIC 8001, Australia.
Teagasc Food Research Centre, Food Chemistry and Technology Department, Moorepark, Fermoy, P61 C996 Cork, Ireland.
Molecules. 2021 Dec 17;26(24):7650. doi: 10.3390/molecules26247650.
This study investigated structural changes in β-casein as a function of temperature (4 and 20 °C) and pH (5.9 and 7.0). For this purpose, nuclear magnetic resonance (NMR) and Fourier-transform infrared (FTIR) spectroscopy were used, in conjunction with chemometric analysis. Both temperature and pH had strongly affected the secondary structure of β-casein, with most affected regions involving random coils and α-helical structures. The α-helical structures showed great pH sensitivity by decreasing at 20 °C and diminishing completely at 4 °C when pH was increased from 5.9 to 7.0. The decrease in α-helix was likely related to the greater presence of random coils at pH 7.0, which was not observed at pH 5.9 at either temperature. The changes in secondary structure components were linked to decreased hydrophobic interactions at lower temperature and increasing pH. The most prominent change of the α-helix took place when the pH was adjusted to 7.0 and the temperature set at 4 °C, which confirms the disruption of the hydrogen bonds and weakening of hydrophobic interactions in the system. The findings can assist in establishing the structural behaviour of the β-casein under conditions that apply as important for solubility and production of β-casein.
本研究调查了β-酪蛋白在温度（4 和 20°C）和 pH 值（5.9 和 7.0）条件下的结构变化。为此，采用了核磁共振（NMR）和傅里叶变换红外（FTIR）光谱技术，并结合了化学计量学分析。温度和 pH 值都强烈影响了β-酪蛋白的二级结构，受影响最大的区域涉及无规卷曲和α-螺旋结构。α-螺旋结构对 pH 值非常敏感，在 20°C 时下降，在 4°C 时完全消失，当 pH 值从 5.9 增加到 7.0 时。α-螺旋的减少可能与在 pH 7.0 时无规卷曲的存在较多有关，在这两种温度下都未观察到 pH 值为 5.9 时的情况。二级结构成分的变化与较低温度下疏水性相互作用的减少和 pH 值的增加有关。当 pH 值调整为 7.0 且温度设定为 4°C 时，α-螺旋发生了最显著的变化，这证实了氢键的破坏和体系中疏水性相互作用的减弱。这些发现有助于确定在β-酪蛋白的溶解度和生产中很重要的条件下的β-酪蛋白的结构行为。
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