الفهرس | Only 14 pages are availabe for public view |
Abstract The world cheese production is markedly increasing unually, parallely the production of calf rennets sharply decreasing because of the sever laws concerning the stop of slautering suckling calves. On the other hand calf holders prefer to fatten their calves to reach 450 kgs to gam more money. Calf rennets produce the best quality of cheeses since it contains higher amount of chymosin enzyme (Formerly rennin) and minor amount of protealytic enzymes (Mainly pepsin) Normally chymosin is responsible for having firm homogeneous coagulant and little pepsin superior lead to ripening, while more pepsin leads to bad quality cheese having pasty texture and bitter flavor. The extraction of rennet from adult animals was done, but the rennet needs great care for cheese processing , since irregular flavors and bitterness markedly appeared especially with long term ripening cheese. Rennet producers tried to extract rennets from plant sources but resultant coagulants. had bad quality cheeses having bitter flavors. Great efforts were paid to produce microbial rennets from bacteria , fungi and yeasts. The resultant coagulants had the higher capacity for clotting the cheese milk but the majority of them caused flavor defects especially with long term ripening cheeses. It is well known that chymosin (rennin) had the ability to produce firm curd, and no off - flavors, oppositely pepsin gave less firm curd, and at long run produce bitter flavor. |