Study On Fed-batch Fermentation Process And Flavor Of Zhejiang Rose Vinegar

Zhejiang rose vinegar is famous for its color like rose,tastes sweet and pure in Jiangsu and Zhejiang.The production of Zhejiang rose vinegar still retains the methods based on natural fermentation and manual operation,there are problems such as long fermentation cycle,high labor intensity and insufficient production efficiency.It is urgent to carry out research and improvement of the process.Fed-batch fermentation can control the intermediate metabolism,improve the conversion rate of substrate to product and so on.In the improvement of Zhejiang rose vinegar brewing technology,the application of supplement fermentation technology has a theoretical basis and application prospects.The subject is applied to the mixed fermentation process of acetic acid multi-strain of Zhejiang rose vinegar by fed-batch fermentation,and the traditional solid saccharification process of rose vinegar is continued to study the feasibility of supplementing the production of liquor in the liquid fermentation stage.The main findings are as follows:Under the laboratory conditions,the effects of alcohol tolerance,feeding time,feeding amount and fermentation temperature on the formation of acetic acid in the fermentation broth of rose vinegar were investigated.The initial alcohol content of the supplement fermentation was 4.5% to 6.5%(v/v): with 6%(v/v)as the optimum condition,the acidity reached 5.13±0.11 g/100 m L at the end of fermentation,and the efficiency of alcohol conversion to acetic acid reached 69.15%.Feeding time: when the initial acidity was 1.5 g/100 m L,the acid production rate was significantly higher than other feeding time.When the initial acidity reached 2.5 g/100 m L,the maximum acidity reached 4.98±0.14 g/100 m L,the amount of acetic acid produced was 20.9% higher than the traditional process.Feeding amount: the production of rose vinegar can be completed when the feed liquor was one third or one half volume,and the highest acidity difference was not significant(P>0.05).Fermentation temperature(26,28,30,32,34℃): fermentation temperature was controlled at 31± 1℃can shorten the fermentation time of acetic acid,increase the amount of acetic acid production,alcohol conversion rate of about 75 %.Amplification test was carried out on the feeding time and the feeding amount after the screening.Under the temperature control of 31±1℃,the initial acidity of 2.5 g/100 m L was supplemented with one half volume of alcohol diluted to 6%(v/v)liquor.At the end of acetic acid fermentation,the highest acidity was 5.48±0.27 g/100 m L,and the efficiency of alcohol conversion to acetic acid was improved,and the amount of acetic acid was increased.And the feeding process had no significant effect on the color formation of rose vinegar.The contents and composition of organic acids in rose vinegar were analyzed by HPLC.The feed fermentation process affected the content of various organic acid components in rose vinegar,but the type of the effect was not significant(P>0.05).Feed fermentation can increase the nonvolatile organic acid content of rose vinegar.The content of non-volatile organic acid in the product fed at 1.5 g/100 m L acidity was 21.18 mg/m L,and fed at 2.5 g/100 m L acidity was increased to 42.10 mg/m L,while the traditional process rose vinegar was 33.61 mg/m L.In the formation of amino acids,the total amount of free amino acids in the fed process(6.10g/100 m L)was higher than that of the traditional process(4.83 g/100 m L),but there was no significant difference in the content of flavor amino acids(P> 0.05),only the initial acidity of 2.5 g/100 m L feeding process of the vinegar umami amino acid content had increased.In general,feeding one half volume of wine liquid at 2.5 g/100 m L acidity was beneficial to the formation of organic acids and amino acids.HS-SPME-GC-MS method was developed for the determination of aroma components in Zhejiang rose vinegar.The optimal extraction conditions were selected,and the aroma components in rose vinegar were effectively quantified by using 2-ethylbutyric acid as the internal standard.The recovery rate of the method was 83.32% to 98.62%.The measured data under the method showed that the content and type of rose vinegar aroma substances changed slightly under the feeding process conditions,and the contents of esters,acids and ketones were greatly improved.