羧甲基纤维素化学结构对乳蛋白稳定性影响

The effect of the chemical structure of CMC on the stability of milk protein

采用异丙醇/乙醇高浴比混合介质体系和单一乙醇介质低浴比体系,分别制备了两种乳蛋白稳定剂羧甲基纤维素CMCm和CMCe。通过乳液体系耐酸、耐盐、稳定性等测试分析,系统研究了两种稳定剂对乳液蛋白的稳定性影响。结果表明,异丙醇/乙醇高浴比混合介质体系得到的CMCm的耐酸、耐盐性好,沉淀率低,乳液稳定期长。通过SEM对乳液形态观察分析表明,添加CMCm的乳液蛋白间形成较均匀连续网络形貌,而添加CMCe的乳液体系则有明显的网路缺陷,蛋白有团聚趋势。为了深入了解两种稳定剂结构对乳液性能的影响,采用核磁共振测试对比研究了CMCm和CMCe大分子链上—CH2COO-基团的分布。研究发现,异丙醇/乙醇高浴比混合体系制备的CMCm,其葡萄糖残基上C-6位羟基的羧甲基化程度较高,而单一乙醇介质低浴比体系得到的CMCe则是C-2位上羟基的羧甲基化程度高。

In this paper,two types of carboxymethyl cellulose samples CMCmand CMCe,used for foodstuffs stability,were prepared in mixed isopropanol and ethanol system at high bath ratio and in ethanol system at low bath ratio,respectively.The stability of two types of carboxymethyl cellulose milk micelle was analyzed by their acid salt tolerance property of these milk beverages.The results showed that the CMCmmilk beverage showed higher ratio of acidity to viscosity（AVR）,higher temperature resistance,lower precipitation ratio（AVR） and better stability.The morphology structure of milk protein was studied by SEM.It showed that the structure of milk protein with CMCmformed continuous network and homogeneous morphology.However the structure of milk protein with CMCeshowed network defects and tendency of aggregation.In order to have in-depth discussion on the structure-property relationship,the distribution of carboxymethyl group on CMCmand CMCewas researched by NMR.The CH2COO^- group on anhydroglucose unit（AGU） of CMCm showed regioselectively substituted at C6,while CMCehad high selectively substituted at C2.