Mozzarella干酪凝乳过程中理化特性及微观结构的变化

为了解牛奶凝乳过程中理化特性及微观结构的变化,研究了Mozzarella干酪凝乳过程中表观粘度、自由巯基含量、流变特性和微观结构的变化,结果表明,加入凝乳酶后,体系中的二硫键即开始减少,至30 min时出现明显增加趋势,而牛奶的表观粘度、弹性模量、粘性模量都在30～40 min出现升高,通过共聚焦激光显微镜可以观察到此时的蛋白质颗粒发生剧烈的凝集;随着凝乳的发展,二硫键生成量增加,凝乳的表观粘度、弹性模量、粘性模量也呈增加趋势,酪蛋白胶束越来越聚集、收缩.通过表观粘度和流变特性测定到的凝乳时间与用共聚焦显微镜观察到的凝乳时间都比较接近,说明3种方法都可用于凝乳时间的客观判断.

Changes of physical-chemical properties and microstructure of Mozzarella cheese during coagulation

In order to find out physical-chemical properties and micro structure changes of milk during coagulation and objective judging methods of gelation time, the apparent viscosity, disulfide bonds content, rheological properties and microstructure of Mozzarella cheese were assessed respectively by viscosimeter, spectrophotometer, rheometer and confocal laser scanning microscopy(CLSM) during coagulation. The results showed that the disulfide bonds content of the milk decreased immediately after the rennet adding, but increased sharply at the time of 30 min. The apparent viscosity, elastic modulust G' )and viscous modulus ( G") all increased obviously at the time of 30 to 40 min, suggesting that the milk started to be coagulated. It was also found that casein granules coagulated violently to form clusters in 38 min by real-time investigations with CLSM. With development of coagulation of milk, more and more disulfide bonds were formed, and the apparent viscosity, G' and G" became bigger and bigger, also the casein clusters became bigger and bigger because of the assembling reaction of casein granules. The gel times calculated from these four methods are pretty close, indicating that all these methods are applicable in judging gelation time of milk.