The Preparation Of Fermented Milk By Lactobacillus Helvetieus And Its Performance Evaluation

This research is mainly the preparation of fermented dairy products by Lactobacillus helveticus and its performance evaluation.Fermented Milk Preparation Process was determined by experiments: fermentation temperature was 41 ?,Lactobacillus helveticus,Lactobacillus bulgaricus and Streptococcus thermophilus was as the species(the ratio between the strains for1:1:1)with a inoculum of 3% and the amount of sugar was 8%.The Rheometer were used to measure the rheological properties of three fermented dairy products,which were made of milk,soybean milk and composite milk.The results showed that three kinds of fermented dairy products were thixotropic fluid,with the hysteresis loop area ratio of 1:0.56:0.69 and a Sticky silk index ratio of 1:0.63:0.91;Under a constant value of temperature and rotate speed,the ratio of initial apparent viscosity was 1:0.99:1.28,there was a slowest rate of decline in apparent viscosity of fermented soymilk;In the strain sweep tests,the stability,from high to low,of the three fermented dairy products was as follows: fermented soy milk,fermented milk and fermented composite milk;During the temperature scan tests,the fermented soymilk had the strongest tolerance of temperature changes,the fermented composite milk had a maximum value of apparent viscosity.By comparing their rheological properties,fermented milk showed a low stability while fermented soybean milk had a strong stability and a low apparent viscosity.Mixed fermented milk not only had a higher apparent viscosity and it also had a higher stability than the fermented milk.A capillary zone electrophoresis method has been developed for the determination of ACE inhibitory activity of fermented milks.After identified the Characteristic peak' position of HHL,then studied the effect of time to ACE catalytic reaction with 3 hours as the reaction result;on the basises of the above experiments,determined the ACE inhibitory activity of two fermented milks which were made of cow milk and soymilk and with the inhibitory rate results respectively as 69.43% and 86.63%.The results not only provided a basic method for fundamental study of different sources of proteins,but also provided a valuable theoretical basis for fermented dairy production.Capillary zone electrophoresis method had potential in studies of rapid determining the ACE inhibitory activity and screening of ACE inhibitors.