Effect Of Rennin Producted From Quambalaria Cyanescens On Physicochemical Properties And Texture Of Cheese

Cheese called as “King of dairy products”, has high nutritional quality andvarious flavor,and concentrates the milk nutrients. Cheese has high additional value,isone of the largest trade products in world dairy products market.However, Cheeseproducts is in the period of marketing expanding,its producting technology is notmature，its variety is very few.Thus, Cheese protects has a market of great potential.This paper considered Quambalaria cyanescens which was screened in theLaboratory condition. The rennin was got from fermentation of this strain,and thenisolated and purified. Cheese was produced by this purified rennin,at the sametime,effects of several factor during production process was studied.Response surfacemethod were carried out to optimize production technology of this soft cheese withour rennin and calf rennin,respectively.Changes of cheese components and proteindegradation during storing period were studied. during cheese storing period,we alsodetermined physical properties of cheese, made a sensory evaluation of its Texturestructure and tastes.This research mainly include the following content:（1） The effects of sterilization method, adding amount of ferment agent, quantityof CaCl₂, curd temperature, pH, amount of rennin to the coagulating property ofcheese were researched.When cheese was sterilized at temperature75℃for15min,curd effect is good,we got ice-cream smooth milk curd with soft texture. OD value ofwhey from the cheese was minimum when adding ferment amount is0.2g/L, quantityof CaCl₂is0.02%, PH is6.3, adding amount of new curd enzyme is for2mL, ODvalue of whey is minimum as the temperature of35℃, and cheese organization wassoft, curd characteristics was better; loss rate of protein is low, quality of cheeseclump is smooth and full of flexibility.（2） We used the response surface method to optimize technological conditions ofproducting cheese. The results show that, when adding ferment amount is0.13g/L,pH is6.5, rennase concentration is2mL and coagulating temperature is33.62℃, ODvalue of whey is0.750, we can get a soft cheese of good product quality and goodtaste.（3） With no resistance to milk powder as raw material,we optimized technological conditions of producting cheese by cattle chymosin. The results showthat, when adding ferment amount is0.2g/L, pH is6.1, rennase concentration is0.002%and coagulating temperature is40℃, OD value of whey is0.681, we can geta soft and flexibility cheese of good product quality. After comparative analysis oftwo enzymes to processing conditions, we find source of new curd enzyme is widely,price is cheap and this curd enzyme can be substituted for cattle chymosin.（4） We measured the content of various components of cheese（1²0d）producted by new rennase and cattle chymosin. The results showed that: in the1²0d inside, water content of two kind of cheese are into decline, fat and total nitrogencontent have appeared first increases, then decreases trend.（5） We researched the protein degradation of cheese producted by new rennaseand cattle chymosin during storage. The results showed that: In the1⁶0d inside,the pH4.6WSN-N content of two kind of cheese has a gradually increasing trend, andthe pH4.6WSN-N content of cheese by new rennase was higher than those of cheeseby cattle chymosin;12%TCA-N content of cheese by new rennase was higher thanthose of cheese by cattle chymosin; To two kind of cheese,5%of PTA-N to totalnitrogen content of each stage was higher than those of the previous stage, the contentof free amino acid in cheese was increased gradually with the extension of mature.The protein content of nitrogen and casein nitrogen of two kind of cheese had agradually decreasing trend; And the levels of peptide nitrogen during storage is rising.（6） Property analysis of two kind of cheese indicated that: In the storage process,hardness of two kind of cheese is gradually decreasing, and each stage, cheese bycattle chymosin had lower hardness than cheese by new rennase. In1¹20d storageprocess, springiness and cohesiveness of two kind of cheese was all down with trend.Sense evaluation was employed to test the two kind of cheese. The result showed thatthere was similar in terms of flavor and texture between the two kind of cheese, butthe structure of cheese by new rennase is loose, how to improve needs furtherresearch.