Study On Fermentation And Flavor Substance In Multi-Strain Douchi

As a kind of food and medicine, douchi is traditional fermented soybean product from ancient time. It is significant to study the mechanism of douchi for mixed fermentation and develop the products which have short producing cycle time, traditional flavour of Chinese douchi and distinct functions. This is full of theoretic and practical importance for changing conditions of producing and consuming of Chinese douchi.A bacterium SY-3with the high fibrinolysin activity and a mold with high β-glucosidase activity were screened from internal fermented soybeans. Qu technology of douchi for mixed fermentation, changes of main active components, volatility flavor substances, physicochemical properties and functional characteristics for preventing mus hyperlipemia of douchi fibrinolysin were studied systemically with the two strains. The results were following:1. The conditions of qu craft for mixed fermentation were optimized according to neutral protease activity.Four-factor orthogonal rotated combination regression based on single factor experiments was finished according to SAS8.0. The optimum fermentation technology were: strains matching ratio (SY-3:AO-1)2.2, inoculation size0.91%at33℃for52h. The neutral protease was61.10u/g. The effect extent to qu craft followed by descending factors including inoculation size, strains matching ratio, fermentation time and temperature.2. The second step fermentation condition was determined by the changes of formal nitrogen during fermentation. The optimum second step fermentation technology was fermenting at30℃for18d in12%salinity.3. The effect factors on volatility flavor substance of douchi were studied for the first time.214volatile components were determineded by GC-MC from20samples. The numbers of these components were32、39、42、42、41、51、45、37、39、35、40、44、35、34、36、38、39、38、41, followed by fermentation time, salt, steaming time and different strains. These compounds included alcohols(26), acids(17), esters(42), aldehydes(6), ketones(10), phenols(10), pyrazines(13), furans(4), furan ketones(3), sulphur-containing compounds(4), acid amides(11) and others. The six kinds of common flavor compounds had been reported with a great contribution on bean condiment flavor were detected in20samples. Direct or indirect relations were supposed between fermentation time and esters and alcohols substances, between salt and furans and pyrazines substances, between steaming time and sulfur compounds and between strains and furans.