Preparation And Study Of Stablity On Directed Vat Set Producing ACE Inhibitory Peptides

Angiotensin-converting-enzyme (ACE) plays an important role in human blood pressure regulation. Excessive ACE can cause the elevation of blood pressure. ACE inhibitory peptides can inhibide ACE activity, keep human blood pressure steady. Probiotics can produce ACE inhibitory peptides during fermentation, which have the advantages of mild antihypertensive effect, persistance, specificity, high safety and lower side effect to human body. So the research on ACE inhibitory peptides has become a new hot spot at home and abroad in recent years. At present, the domestic research mainly focus on the preparation of ACE inhibitory peptides from food, and yoghurt starter cultures of ACE inhibitory peptides are scarce studied. The main purpose of the research was to prepare functional Directed Vat Set with probiotics producing ACE inhibitory peptides. It was aimed at the preparation of acid dairy products containing ACE inhibitory peptides, and the products could regulate blood pressure. It would provide technical support for the development of functional dairy.In the study, the five probiotics were selected and prepared into freeze-dried powders according to previous technology of study group, including Lactobacillus bulgaricus LB6 and Lactobacillus plantarum L69 producing ACE inhibitory peptides, and Streptococcus thermophilus ST78, Bifidobacterium bifidum BB01 and Lactobacillus acidophilus LA5 which had good freeze-dried survival rates. pH, OD value and ACE inhibitory activity were as index, seven kinds of starter cultures were gained by single-factor experiment and response surface method. The stability of each starter culture was studied by accelerated test. The yogurt could been obtained according to the optimal conditions of fermentation, and the ACE inhibitory activity, stability, total viable counts and sensory score of yogurt were measured. The results were as follows. 1. Cow milk series of DVS producing ACE inhibitory peptidesA. The regular starter culture were the combination of freeze-dried LB6 and ST78 powders. Cow milk was as fermentation matrix. The optimal conditions of ordinary starter culture were inoculum size 0.3%, LB6:ST78=3:2,42℃for 4.5 h by single-factor and response surface experiments. The cow yogurt was gained according to the optimal conditions of fermentation, whose shelf life at 4℃, total viable counts, ACE inhibitory activity and sensory score respectively were 48 d,2.93×109CFU/mL,84.45% and 89 points. The result of accelerated test showed that the shelf life of ordinary starter culture was 1095 d at-18℃.B. The ordinary starter culture (LB6:ST78=3:2) and freeze-dried L69 powder were combined, and the P starter culture was gained. Cow milk was the fermentation matrix. The optimal conditions was gained by single-factor and response surface experiments, and the result showed that inoculum size 0.2%, ordinary:L69=1:2,42℃for 4.5 h. The cow milk was fermented according to the optimal conditions. For the yogurt, the shelf life was 50 d, the total viable counts was 4.92×109CFU/mL, the ACE inhibitory activity was 87.20% and the sensory score was 88 points. The shelf life of P starter culture was obtained by accelerated test, the result was 1257 d at-18℃.C. The P starter culture (ordinary:L69= 1:2) and freeze-dried BB01 powder were combined, and the BP starter culture was gained. Cow milk was the fermentation matrix. With single-factor and response surface experiments, the optimal conditions were inoculum size 0.3%, P:BB01=1:1 and 42℃for 5 h. The cow milk was fermented according to the optimal conditions, and the shelf life, total viable counts, ACE inhibitory activity and sensory score of yogurt respectively were 42 d,1.83×109 CFU/mL,76.51% and 84 points. With accelerated test, the shelf life of BP starter culture was 992 d at-18℃.D. The ABP starter culture was the compound of BP starter culture (P:BB01=1:1) and freeze-dried LA5 powder. Cow milk was the fermentation matrix. With single-factor and response surface experiments, the optimal conditions were inoculum size 0.3%, BP:LA5=1:1 and 42℃for 5 h. The ABP yogurt was gained according to the optimal conditions of fermentation, and the shelf life, total viable counts, ACE inhibitory activity and sensory score respectively were 45 d,2.83×109 CFU/mL,75.12% and 86 points. The shelf life of ABP starter culture was 1012 d at-18℃.2. Goat milk series of DVS producing ACE inhibitory peptidesA. The result of single factor and response surface experiment showed that the best conditions of regular starter used in fermentation of goat milk, the conditions were inoculum size 0.4%, LB6:ST78=1:1 and 42℃ for 5.5 h. The goat yogurt of regular starter was gained with the best conditions of fermentation, and the shelf life, total viable counts, ACE inhibitory activity and sensory score respectively were 40 d,1.67×108 CFU/mL,87.84% and 92 points. The result of accelerated test showed that the shelf life was 951 d at-18℃.B. The P starter culture was the compound of regular starter (LB6:ST78=1:1) and freeze-dried L69 powder. The optimal conditions of P starter culture used in fermentation of goat milk were that inoculum size was 0.3%, regular:L69=1:1,42℃ for 5 h. The goat yogurt of P starter was gained with the best conditions, and the shelf life, total viable counts, ACE inhibitory activity and sensory score respectively were 41 d,2.07×108 CFU/mL,89.94% and 90 points. The shelf life was 955 d at-18℃ by accelerated test.C. The AP starter culture was the compound of P starter (regular:L69=1:1) and freeze-dried LA5 powder. With single factor and response surface experiment, the optimal conditions of AP starter used in fermentation of goat milk was gained. The conditions were that inoculum size 0.4%, P:LA5=2:3, 42℃ for 6 h. The AP goat yogurt was was gained with the optimal conditions, and the shelf life, total viable counts, ACE inhibitory activity and sensory score respectively were 38 d,1.33×108 CFU/mL,84.71% and 87 points. The shelf life of AP starter was obtained by accelerated test, the result was 983 d at-18℃. 3. In the four kinds of compound starter cultures used in cow milk fermentation, P starter culture had the best effect of application, regular starter culture was the second, the third was BP starter culture, and the last was ABP starter culture. P cow yogurt had the best ACE inhibition activity and sensory score. In the three kinds of compound starter cultures used in fermentation of goat milk, P goat milk starter culture was the optimal in the effect of fermentation, the second was regular goat milk starter culture, and the third was AP starter culture.The DVS producing ACE inhibitory peptides had higher ACE inhibition activity, well storage stability and good fermentation performance in the research. It would provide technical support for the development of functional dairy.