| Malolactic fermentation(MLF) is the key productive step to reduce the acidity and let the taste of wine balance. The aromatic composition of wine was changed and the stability and quality of products would be improved after MLF. It has an important significance for keeping the terrior characters of wine to filter the fine strains from the lactic acid fermented products of wine regions. 5 kinds of traditional lactic acid fermented food were selected from wine region of Gansu province during experiment. MRS culture medium has been used to separate MLF lactic acid bacteria, and the strains were preliminarily identified according to the morphological characteristics and the phenomenon of physiology biochemistry. Then, the excellent strains were confirmed as genetic resources by the assessment of transformability between malic acid and lactic acid. At last, the fermentation property of optimizing strains was analysed. The main results showed:1. 58 strains were isolated and purified according to the calcium dissolving ring, the morphology and physiological-biochemical characteristics from yogurt, pickles, sweet oats,jiangshui and wine on MRS culture medium. Among them, 38 strains were bacilli and 20 strains were cocci.2. The conversion of malic acid and lactic acid were detected by high performance liquid chromatography from 58 filtered strains. the results showed16 strains have higher degradative ability of malic acid, among them, SN13 and SN19 came from yogurt, PC1, PC2 and PC5 came from pickles, JS1, JS2, JS4 and JS7 came from jiangshui, PTJ1, PTJ4, PTJ5, PTJ6,PTJ9, PTJ10 and PTJ11 came from wine.3. The strains’ tolerance of pH, alcohol and SO2 were evaluated by adjusting their concentration in ATB culture medium, the assessment criteria was the reproductive amount of lactic acid bacteria. The results showed: the tolerance of PC5, SN13, PTJ1, PTJ5 and PTJ9 were, pH 3.0, alcohol 16%, SO2 80 mg/L. And then, PTJ1, PTJ5, SN13 were selected by thecomprehensive tolerance evaluation from orthogonal experiments, the tolerant order of pH,alcohol and SO2 was pH﹥SO2﹥alcohol. PTJ1 was excellent strain resource by comparing the dry red wine fermentation characteristics of filtered strains, conserved it and analysised of the wine sample volatile components.4. The fermentative characteristics of optimalizing malic acid, lactic acid fermentative strains in red wine were analysed, the results showed: MLF can be completed in 10 days by PTJ1, volatile acid of the product was less than 0.5g/L, soft index was greater than 5.5, the sensorial evaluation was fine, so PTJ1 was an excellent malic acid-lactic acid fermentative strains. The composition and proportion of volatile component were changed in wine by MLF formentation of PTJ1. The release of phenylethyl alcohol and isoamyl alcohol were advanced,linalool and caproic acid isoamyl acetate were generated. Isobutyric acid and cis-4-decylene-1-alcohol disappeared. The sample had good bouquet, fruital and floral aroma.MLF could improve the aromatic quality of wine.5. The optimalizing strain PTJ1 was Lactobacillus plantarum according to the morphology, physiological-biochemical characteristics and 16 S rDNA identification. |
PDF Full Text Request