Strains Screening Of Acetic Acid Bacteria And Optimazation Of Fermentation Process For Malt Vinegar

Vinegar is one of the common candiments for consumer all of the world, in China, people often eatcereals vinegar produced by corn, sorghum,et al, while in western countries, barley is often produced asraw material for brewing vinegar fermentation. Malt vinegar is one of the traditional vinegars in Europewith a long history, which was prepared by barley malting, saccharification, alcoholic fermentation andacetic acid fermentation process. But this product is rare in our market and few studies have beenreported.For malt vinegar, wort saccharification process was firstly considered to degradate the starch andprotein sufficiently by controlling the temperature and time. The process was as follows: the malt flourwas thoroughly mixed with approximately4volumes of water at40℃for0.5h to yield a mash, thenkept the mash at50°C for1.5h to digest the protein fully, and subjected to mashing at65℃for5h toachieve a higher content of reducing sugars16.32g/100mL, alpha-amino nitrogen content290.2mg/L;For strains screening of acetic acid bacteria for malt vinegar production, different strains A0, A1,A2, A3from different sources were respectively inoculated in wort alcoholic broch of alcoholconcentration6.0%(v/v) firstly, we selected strains A0, A3in the case of acetification rate andpreferable flavor sensory. Then strains A0, A3were respectively inoculated in wort alcoholic broch ofalcohol concentration3.0%(v/v) and9.0%(v/v) in order to investigate the fermentation performance.The results was showed that in alcohol concentration of3.0%(v/v)~9.0%(v/v), the averageacetification rate of strain A0reached0.35g/L·h, verifying the fermentation performance of strain A0was stable, while the acetification rate of strain A3reduced with the increasing of alcohol concentrationsignificantly, so strain A0was suitable for malt vinegar productionIn order to produce high quality malt vinegar, we used single factor experiment and Design-Expertsoftware to optimize fermentation process which was showed as follows: the initial wort concentration20Bx, inoculum size5%(v/v) of Saccharomyces cerevisiae, the fermentation temperature of30℃, pH4.3, we produced wort alcoholic broch of alcohol concentration of6.0%(v/v) after36h. Then theparameters of the inoculum size12%(v/v), shaking culture with190r/min in32℃for5days wasoptimized for acetic acid fermentation process. We got malt vinegar with acidity of4.20g/100mL.In this study, sensory quality of malt vinegar was evaluated through color, aroma, taste and style,using the scoring system. Evaluation results was showed that these products produced strong vinegar odor and rich tast in common, while the malt flavor characteristics of the homemade malt vinegar wasmore prominent, and the taste of the commercial malt vinegar was more abundant. The features of maltvinegar production mentioned above would help control product quality in the future.Comparing with the commercial malt vinegar on normal physicochemical properties and organicacids studies, malt vinegar we produced had higher levels of acetic acid, the content of sugar2.20g/100mL and total ester1.50g/100mL were also higher, while the commercial malt vinegar containshigh level of soluble solids4.0g/100mL.The homemade malt vinegar possessed oxalic acid, tartaric acid,acetic acid and succinic acid, while commercial malt vinegar contained oxalic acid, lactic acid, aceticacid, succinic acid. The differences of organic acids showed in the two products gived rise to thedifferences in flavor and taste system.