Identification And Screening Of Lactic Acid Bacteria And The Influence On The Characteristics Of The New Semi-hard Cheese

The lactic acid bacteria were isolated and identified from twelve cheesesamples,which were collected from outside country and inner Mongolia. The lactic acidbacteria were screened and used as cheese starter culture of Chinese tastescheese.Through studying the value changes of physico-chemical characterization andmicroorganism.The results were as follow:37strains of lactic acid bacteria were screenedfrom the samples, Among them4strains were better by detecting some fermentedcharacteristics(for example acid production,salt tolerance,sensory evaluation ofcheese,texture of cheese,the moisture of the cheese,whey output, fermentedcharacterization of skim milk during14hours). And then the four strains were identifiedby traditional physio-chemical and API50CH and16SrDNA molecular methods, Theresults indicated that K2strain and D1strain were Lactobacillus.the K2strain isLactobacillus.Plantarum and the D1strain is Lactobacillus. Sakei,and the other twostrains G1and F1were Lactococcus，and the G1strain is Enterococcus.faecium,the F1strain is Lac. lactis subsp. Cremoris.The influence of4lactic acid bacteria strains were used as starter according todifferent proportion and amount to processed semi-hard cheese, according to assayingviscosity and acid conditions in fermented milk.and then the best proportion and amountwere decided,which were the proportion K2and F1=5:1was much higher than that of K2or F1alone at the time of stable stage, and the amount was5%,and the same time anothergroup was selected,that was D1and G1=1:1was much higher than that of D1or G1alone at the time of stable stage,and the amount was2%,and then the two best groups ofthe four strains on the characeristics of semi-hard cheese were discussed.the two groupstrains had been added in cheese.Testing various physical,chemical and microbialindicators during cheese ripening process,and result showed that the addition of staterstrains had changed the general characteristics of semi-hard cheese,such as the contentof moisture and the value of pH and the texture and pH4.6SN and12%TCA SN and thecontents of total free amino acid and the individual free amino acid in the experimentalcheese were significantly different from the control(P<0.05). the pH4.6SN and12%TCA SN and the contents of total free amino acid and the individual free amino acid increase obviously during the ripening period of the cheese.and the pH value reducedrapidly during2months in the two group experimental cheeses,lately it rised slowly andkept invariable.The number of microorganisms decreased rapidly early and kept stableeventually.In addition,the group of K2F1increased the hardness and reduced thespringing of products significantly during the ripening period of the cheese,and thecolour of cheese was significant effected by the starter culture of K2F1during theripening period.As the result,the strains of K2F1can be used as starter in cheese.