Study On The Quality And Safety Of The Semi-hard Cheese During Ripening Process In Different Maturation Conditions

The research studied physicochemical properties and organoleptic qualities of semi-hard cheeseduring ripening period by vacuum package and waxing. And the variation of the semi-hard cheese duringmaturation quality was analyzed; Denaturing Gradient gel Electrophoresis (DGGE) methods were used toexamine microbial flora changes during cheese ripening; Finally, the changes in the content of biogenicamines in the two kinds of cheese ripening process were studied.The aim is to provide some theoreticalbasis to improve and enhance the quality and safety of the semi-hard cheese. Main contents andconclusions are as follows．1. The study of the physicochemical properties of semi-hard cheese during ripening.The change of quality of semi-hard cheese was studied during cheese ripening. The results showedthat the value of pH decreased firstly, and then increased slowly. The content of moisture and the value ofhardness decreased. The exchangement of content of free calcium and phosphorus were in dynamic balance,a negative correlation between them. The content of pH4.6soluble Nitogen,the content of12%TCA solubleNitogen,the total content of free amino acid,the content of free fatty acids and the fragments of peptide andsmall peptide increased gradually while the single amino acid changed simutanous. At last the valine,leucine, lysine were the main amino acids in the cheese. The maximum value of sensory evaluation ofcheese was found on the75th day.The results show that the cheese moisture content of the cheese ripening process of vacuum packagingand waxed packaging has a downward trend and the difference was significant (P <0.05), the value of pHdecreased firstly, and then increased slowly. The content of pH4.6soluble Nitogen,the content of12%TCAsoluble Nitogen,the total content of free amino acid,the content of free fatty acids and the fragments ofpeptide and small peptide increased gradually while the single amino acid changed simutanous. At last thevaline, leucine, lysine were the main amino acids in the cheese. The maximum value of sensory evaluationof cheese by vacuum package was found on the75th day, and the maximum value of sensory evaluation ofcheese by waxing was found on the60th day, and then begins to decline.2. The microbial flora changes during semi-hard cheese ripeningBoth culture-dependent and denaturing gradient gel electrophoresis (DGGE) methods were used toexamine microbial flora changes during cheese ripening. The results showed that the number of totalbacteria and lactic acid bacteria increased firstly, then decreased slowly. E. coli decreased rapidly, and thenincreased slowly. Yeast increased during cheese ripening. The study showed that the dominant bacteria wassignificantly changed after fermentation, the dominant bacteria change significantly vacuum-packed cheeseSwiss Lactobacillus become absolutely dominant bacteria and waxed packaging cheese ripening late SwissLactobacillus casei flora.3. The changes of biogenic amines during ripening of semi-hard cheeseThe changes of biogenic amines during ripening of semi-hard cheese which were packaged by vacuum package and waxing were studied in this paper. Biogenic amines were determined by HPLC. The resultsshow that: the entire cheese ripening process, two packaging cheese detect tryptamine, phenylethylamine,putrescine, cadaverine, histamine and tyramine, biogenic amines and waxed packaging cheeseconcentrations are always higher than the formation of biogenic amines in vacuum-packed cheese generalupward trend with the prolongation of maturation time, but its formation is very low, far below the toxicitythreshold of biogenic amines1000mg/kg.