柠檬酸钠对谷氨酰胺转移酶山羊乳凝胶特性影响的光谱学分析

Spectroscopic Analysis of Effect of Sodium Citrate on the Properties of Transglutaminase Goat's Milk Gels

运用多重光散射光谱、多散斑扩散波光谱和动态光散射光谱分析了柠檬酸钠(TSC)对谷氨酰胺转移酶(TG酶)山羊乳凝胶特性的影响。将浓度分别为0,20,40,60和80mmol·L^(-1)的TSC加入到脱脂羊乳中,经过TG酶处理后进行酸化凝乳。凝乳形成过程中,动态光散射光谱显示,随着TSC浓度的增加,酪蛋白胶束的直径从(142.0±11.2)nm下降到(24.4±2.1)nm;在凝胶形成的前5h内,在不同TSC浓度条件下,样品的背散射光强度分别从41.9%±0.3%,35.8%±0.4%,25.3%±0.5%,10.6%±0.3%和5.3%±0.4%,增加到55.8%±0.6%,49.5%±0.5%,41.9%±0.4%,37.8%±0.4%和30.8%±0.3%,表明TSC的浓度越高,凝胶体系中颗粒的尺寸越小,形成的凝胶构筑单元越小;同时,多散斑扩散波光谱的均方位移曲线显示,凝胶的突变时间分别为31,74,98,151和226min,表明TSC的浓度越高,山羊乳凝胶形成时间越长;凝胶的持水力与硬度值分析发现,TSC将羊乳酪蛋白胶束分解成更小的颗粒,在TG酶作用下形成更多的共价键连接位点,形成的凝胶具有更高的硬度和持水能力。

In this study, the effect of sodium citrate （TSC） on the characteristics of transglutaminase （TGase） goat milk gels was analyzed using multiple light scattering, multiple speckle diffusion wave spectroscopy, and dynamic light scattering spectroscopy. TSC was added to skimmed goat milk to concentrations of 0, 20, 40, 60, and 80 mmol·L-1, and the milk was acidified by gluconolactone （GDL） after TG enzyme treatment. Dynamic light scattering spectra indicated that on increasing the TSC concentrations in the range of 0 to 80 mmol·L-1, the diameter of casein micelles decreased from （142.0±11.2） to （24.4±2.1） nm; The intensity of the backscattered light was increased from 41.9%±0.3%, 35.8%±0.4%, 25.3%±0.5%, 10.6%±0.3%, and 5.3%±0.4% to 55.8%±0.6%, 49.5%±0.5%, 41.9%±0.4%, 37.8%±0.4% and 30.8%±0.3%, respectively, indicating that the higher the concentration of TSC, the smaller the size of the particles in the gel system, and the smaller the gel building units formed; At the same time, the mean square displacement curves of the multi-speckle diffuse wave spectrum showed that the gel mutation time was 31, 74, 98, 151 and 226 min, respectively, indicating that the higher the concentration of TSC, the longer gelation time. The water holding capacity and hardness values of the resulted gels was negatively related to the TSC concentrations.