Xinjiang Tacheng Kazak Traditional Cheese Physicochemical And Non Starter Lactic Acid Bacteria Effect On Cheese Flavor

Xinjiang is a multi-ethnic region, most of the ethnic minorities have the habit of making and eating cheese.From the beginning of the nomads and herders have begun using lactic acid bacteria fermentation production of fermented dairy products to eat a balanced diet, after thousands of years of natural domestication of the fermentation strains(mainly lactic acid bacteria) are extremely rich, lactic acid bacteria in traditional fermented milk products, especially with excellent characteristics and probiotic strains of lactic acid bacteria is therefore preserved, changes in the cheese flavor changes its own mature in the process of non starter lactic acid bacteria closely related.The test from the Kazakh traditional cheese with traditional method for isolation and identification of excellent traits of non starter lactic acid bacteria screened, choose different genera with a representative strains into the non traditional way of making cheese and regularly of cheese in the non volatile substances and use GC MS and electronic nose technique for the determination of volatile matter, analysis of nslab influence of cheese ripening period flavor. Draw the conclusion as follows:(1) physical and chemical indicators, quality of Kazakh traditional cheese texture, flavor substances were determined. The results showed that the hardness and the fat, protein and ash content showed a positive trend, while the moisture content was inversely proportional to the trend. The results of the relative molecular weight of the protein in cheese by SDS-PAGE showed that the protein molecular mass was two KD and 32 KD, which belong to the molecular weight of the protein. Using GC-MS to detect volatile flavor compounds are mainly carboxylic acid(7 species), aldehydes and ketones(7 species), esters(7species), alkanes(6), alcohols(4 species). Esters are the main flavor substances, ethyl ester is more content in milk samples.(2) collected from Xinjiang Tacheng area 10 copies of Kazak herdsmen homemade cheese as the research object, the screen of non fermentative agent lactic acid bacteria strain 43, including 32 strains of Staphylococcus aureus, 11 strains of Bacillus, producing protease has 32 strains, reached 74.4%. Combined with the physiological and biochemical characteristics, we select 10 strains with excellent traits of nslab,using 16 S r DNA sequence homology analysis and established the phylogenetic tree analysis was identified by molecular identification showed that: 3 strains of Staphylococcus epidermidis; 2 strains of lactic acid strain Pediococcus acidilactici); 1 strains of Pediococcus pentosaceus Pediococcus pentosaceus); 1 strain of Lactobacillus casei; 2 strains were rhamnose lactobacillus(Lactobacillus rhamnosus).(3) select three different genera of nslab cheese making, these three kinds of bacteria are R3-5(Pediococcus acidilactici), R4-2(Staphylococcus epidermidis), R9-6(Lactobacillus rhamnosus), plus a blank control group, before adding the rennet into with three kinds of bacteria fermented milk in. To 60 days period, every 10 days determination once, can draw the cheese with the ripening time increases the moisture content decreased; p H value firstly decreased and then increased, to 40 days time tends to balance,protein and fat content showed an upward trend; free fatty acid showed a trend of upper; the total number of lactic acid bacteria is showing a downward trend. Can be seen through the SDS-PAGE protein electrophoresis, R9-6 and the blank sample difference is biggest, the difference between R4-2 and the blank sample is the smallest.(4) in the cheese ripened in 20 day, 40 day, 60 day were to detect volatile flavor substances measured mainly carboxylic acids, aldehydes and ketones, esters, alkanes, alcohols and other material. Combined with electronic nose on the mature cheese were measured and analyzed, R4-2 and blank samples have a certain similarity in smell, R3-5 sample and R9-6 sample odor and the difference between the difference.Addition of nslab influence on volatile flavor compounds in cheese late production, its influence the orderof magnitude Lactobacillus rhamnosus > Pediococcus aureus > Staphylococcus epidermidis, join the Staphylococcus epidermidis cheese and blank sample in flavor basically no much difference, which bacteria of the genus non starter lactic acid bacteria on flavor greater impact.