| Yellow serofluid(liquid waste) is the main byproduct produced in the fermentation process of Luzhou-flavor liquor, which consists a variety of flavor components such as organic acids, alcohols, esters etc.. It was converted into yellow serofluid esterified liquid by aroma-producing microorganisms, and subsequently was used as seasoning liquid or cross-steamed with fermented grains in distillery to improve the quality of liquor, Present experiments may be helpful to reduce the production costs of liquor industry.In present study, 17 yeasts and 5 moulds were used as aroma-producing microorganisms, from which the high ethyl caproate producing microbes were selected by artificial esterifying and yellow serofluid esterifying systems. Then the microbes selected were combined to produce aroma-producing bran qu. The parameters of aroma-producing bran qu and esterifying condition in yellow serofluid were optimized in present study. Thereafter, experiments in medium-sale were performed at two enterprises producing Luzhou-flavor liquor. The main findings are listed as follows:(1) Microorganisms groups of aroma-producing bran qu and combination models: which were established as an equimolar mixture of a yeast H1Y-24 cultured in YPD liquid medium and a mould G4M-10 cultured in bran, The mixture were applied in yellow serofluid esterifying system, and the resulting ethyl caproate concentration was 120.95±4.77 mg/100 mL, 8.10 times higher than the control, and the concentration of ethyl acetate in esterifying liquid increased 0.34 times, that of ethyl butyrate increased 11.70 times and ones of ethyl lactate decreased 0.08 times, Ethyl lactate and ethyl caproate ratio decreased from 22.60 to 2.30, improving the rationality of 4 esters above in esterifying liquid. Volatiles in aroma-producing bran qu(dry qu)were analyzed, results indicated that vinyl guaiacol produced dry qu, accounted for the total flavor 36.69 %.(2) Groups of microbial identification of aroma-producing bran qu: Phylogenetic analysis of H1Y-24 and G4M-10 showed that H1Y-24 and G4M-10 belonged to the first class classification of Pichia sp. and Monascus purpureus.(3) By single-factor and orthogonal test, the optimal production parameters of aroma-producing bran qu was as follows: M. purpureus G4M-10 culture material powder 36 %(bran 40 mesh sieve,w/w), initial moisture 50 %(w/w), the spore suspension inoculation 4 %(v/w), temperature 32℃, incubation 84 h, at this time, added H1Y-24 bacterial suspension to G4M-10 and adding amount of 0.6 ml/g qu(the cell concentration 108 /mL), mixed well and dried at 35℃ for 4 h, and then sealed for preservation. Under these conditions, the concentration of ethyl caproate generated in artificial esterifying system was 6.71±1.47 mg/100 m L, 6.37 times higher than the control. In yellow serofluid esterifying system, the concentration of ethyl caproate was 128.13±5.13 mg/100 m L, 4.60 times higher than the control.(4) By single-factor and orthogonal experiment, the optimal parameters of aroma-producing bran qu for esterifying yellow serofluid was listed as below: added 6 %(95 %,v/v) of ethanol into the pretreated yellow serofluid, 6 %(w/v)of aroma-producing bran qu, the reaction temperature was 32℃. Based on these esterifying parameters, the yellow serofluid collected from four pits with different ages were esterified, compared with the control, the concentrations of ethyl caproate increased 47.75 times, 22.69 times, 32.20 times and 18.07 times.(5) Experiments in medium-sale were carried out at Sichuan Huaxia Liquor Industry Co. Ltd. and Zhuhai Liquor Industry Co. Ltd respectively. The results showed that the concentration of ethyl caproate in the yellow serofluid treated with aroma-producing bran qu increased 8.32 times and 3.89 times respectively, that of ethyl butyrate respectively increased 6.62 times and 3.14 times, while that of ethyl acetate and ethyl lactate steady stable or even declined, improving the balance of 4 esters above in esterifying liquid. The concentration of ethyl caproate in the liquor obtained by cross-steaming Zaopei with esterified liquid increased by 33.81 mg/100 mL and 27.78 mg/100 m L respectively. And the contents of β-phenethyl alcohol eliciting special odors increased by 1.96 mg/100 mL and 0.96 mg/100 mL. By the sensory evaluation, liquor treated with bran qu had more complex pit-flavor and tastes, and less astringent odors.In summary, aroma-producing bran qu can converted yellow serofluid into fermented materials for enhancing the liquor quality by cross-steamed with fermented grains in distillery, turning waste products into a positive resources, as a results, it has great application prospects. |
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