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Kazakh cheese is a traditional dairy product in Xinjiang, China. The function and potential probiotic characteristics of Saccharomyces cerevisiae DL6–20 and Kluyveromyces marxianus B13–5 in Kazakh cheese and its contribution to cheese fermentation was studied. In this study, the effect of the addition ratio of gamma aminobutyric acid (GABA)-producing S. cerevisiae DL6–20 and K. marxianus B13–5 on cheese quality was investigated. Cheeses were prepared by fermentations with a total of six treatments: comercial culture alone as control (CS), a combination with one yeast, either; K. marxianus B13–5 (CSM); S. cerevisiae DL6–20 (CSS); and three different proportions of this two yeasts (CSM:CSS 1:1, 1:2, 2:1). We measured the GABA content of cheese, as well as basic physical and chemical indicators, microbial content, free amino acid (FAA) content, texture, and flavor compound content. The total FAA content of mixed bacteria fermentation was higher than that of the single bacteria alone. The GABA content CSM:CSS 1:2 GABA content was 0.114 g/100 g, CSM:CSS 2:1 GABA content was 0.12 g/100 g, CSM:CSS1:1 content of GABA produced in the late ripening period of cheese was the highest, reaching 0.189 g/100 g and the number of LAB and yeasts in CSM:CSS 1:1 was higher than that of other cheeses. The mixed-strain fermentation generally produced cheeses with a higher protein content than that of the single-strain fermentation in the late stage of the maturation process, especially the protein content of CSM:CSS 1:1 during the ripening period, when the protein content was highest at day 50. CSM:CSS 1:1 had a low moisture content, making it easy to store. With the exception of water and protein content, there is no significant difference in other physical and chemical indicators. CSM:CSS 1:1 contributed to the formation of cheese texture. In addition, multivariate statistical analysis indicated that mixed-strain fermentation was beneficial to the production of cheese aroma, with the aroma production performance of CSM:CSS 1:2 and CSM:CSS 2:1 found to be better than that of CSM: CSS 1:1. [ABSTRACT FROM AUTHOR]

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Cereal vinegar, a traditional acidic condiment in China. The quality of cereal vinegars varies depending on the raw materials used to produce them, fermentation methods and brewing environments. To investigate the microbial community succession and metabolite changes on the whole fermentation process of traditional cereal vinegar in Xinjiang, we analyzed it by high-throughput sequencing, high-performance liquid chromatography and head space solid phase micro-extraction-gas chromatography-mass spectrometry technology. The acetic acid (5733.33 mg/100 g), lactic acid (1265.33 mg/100 g) and succinic acid (520.00 mg/100 g), gallic acid (63.09 μg/g) and vanillic acid (29.05 μg/g) were the dominant organic acids and phenolic compounds in traditional cereal vinegar of Xinjiang, respectively. In later stage of aging, high levels of acetoin, ethyl phenylacetate, phenylethyl alcohol and ethyl lactate endowed the cereal vinegar with rosy, fruity and creamy aroma. The functional fungal genera were Saccharomyces , Fusarium and Kazachstania , and the functional bacterial were Pseudomonas , Lactobacillus , Acetobacter , Rhodococcus and Methylobacterium. Spearman's correlation coefficient showed that bacterial community had a strong correlation with various flavor compounds. The results could provide a theoretical reference for flavor enhancement and process improvement of traditional cereal vinegar in Xinjiang. [Display omitted] • The four fermentation stages of cereal vinegar were comprehensively studied. • Acetic acid, lactic acid and succinic acid were main organic acids of cereal vinegar. • Gallic acid and vanillic acid were the main phenolic compounds of cereal vinegar. • The AAF and AS were the main stages for the accumulation of flavor substances. • The functional bacterial genera were Pseudomonas, Lactobacillus and Acetobacter. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effects of NSLAB on Kazakh cheese ripening was studied. • Cheeses made using P. acidilactici , S. epidermidis , and L. rhamnosus were prepared. • NSLAB cheeses had different protein contents, free fatty acid contents, and pH. • NSLAB cheeses had different flavor compounds and odor profiles (volatile components). • NSLAB can be used as an adjunct starter to make Kazakh cheese. Xinjiang is a multiethnic region of China. Traditionally, most ethnic minorities are known to produce and consume cheese. Nomadic people have been reported to use lactic acid bacteria (LAB) for decades to produce fermented dairy products as part of a balanced diet. Non-starter LAB (NSLAB) contribute to different degrees of ripening, depending on the cheese variety. In the present study, we screened three types of NSLAB with good proteolysis and autolytic abilities from traditional Kazakh cheese: Pediococcus acidilactici R3-5, Staphylococcus epidermidis R4-2, and Lactobacillus rhamnosus R9-6. A control (no NSLAB) was also included, resulting in four distinct types of cheese samples. We used gas chromatography-mass spectrometry and the electronic nose system to identify volatile compounds and analyze the effect of NSLAB on cheese flavor at the ripening stage. The physicochemical indicators changed significantly during the ripening of Kazakh cheese. Compared with the control, the protein content, free fatty acid content, pH, flavor compounds, and odor profiles of the test cheeses were significantly different. The major chemical differences among cheeses were the synthesis of some key volatile components (ethyl caprylate, ethyl caprate, myristyl carbonate, capric acid, caprylic acid, nonanal, and benzyl alcohol). NSLAB can be used as an adjunct starter to make Kazakh cheese and the use of NSLAB affected the cheese flavor quality positively. [ABSTRACT FROM AUTHOR]