The Study On The Application Effect Of Different Milk-clotting Enzymes During Cheesemaking

In this experiment the source is the freshmilk produced by xi'an changxing Dairy with import EZAL and MAO 11 from abroad as yeast powder (str. Cremoris and Str. Lactis) Use microbial rennet, swine pepsin, lamb rennet, calf rennet, papain and ficin as milk-clotting enzymes to produce hard cheese. And research the effect of different milk - clotting enzymes to cheese yield ,cheese hardness and proteolysis during ripening.Yield experiments showed that the yields of group lamb rennet and calf rennet and microbial rennet (10.86%, 10.80%, 10.60%, respectively) were significantly higher than that of group swine pepsin, chymopapain ficin(10.36%,9.84%,9.76%respectively).It showed that different enzymes affect heavily serum propotion in the process, that is Nafrients followed serum ficin are most if treated with ; much less calf rennet, least with chymopapain, The result has connection with activity of rennet and different characteristics of hydrolyzed casein.Different rennets affect FAA contain in the course of hard cheese ripening , the ninetieth day of ripening, calf rennet is the most; calf rennet is less, chymopain is the least. The result of cheese firmness evaluation during ripening the first 15 days of ripening and then slowly. The cheese firmness among six treatments had no significant different at any sampling time of ripening (P>0.05)].The ratio of PH4.6 WSN, 12%TCA-N and 5% PTA-N to TN were measured at 0, 15, 30,60 and 90 of ripening, The results showed that the PH4. 6WSN, 12%TCA-N contents in creased significantly with the ripening time, The significant difference of pH4.6 WSN among six treatments occurred at 60th and 90th. The content of pH4.6 WSN in group microbial rennet, calf rennet was the highest; chymopapain and ficin was lowest, and the group swine pepsin was higher . The third was significant difference in 12% TCA-N contain among three groups at the 90th of ripening and group calf rennet, microbial rennet were higher than group, chymopapain , but had no significant difference with calf rennet and swine pepsin. The content of 5%PTA-N in every ripening had difference With difference milk - clotting enzymes. Proteolysis data revealed that the proteolytic ability ofmicrobial rennet is the highest during repenting, chymopapain and swine pepsin and calf rennet remained moderate, chymopapain and ficin were the least.It can be conduded from the experiment that lamb rennet had excellent characteristics in milk cheesemaking, calf rennet and microbial moderate ficin and chymopapain were the least, which result in low yield, rough feature, bitter flavor, and had no practical use in production.