Study On Brewing Technology Of Apple Vinegar Containing High Concentration Of Lactic Acid

Strain screening and technology optimization are vital to apple vinegar production.They influence the ultimate acidity and quality of apple vinegar.However,few studies on application of lactic acid bacteria in fruit vinegar and process development for brewing high acidity apple cider vinegar has been published.In addition,the yield of the strain is low and the flavor is not harmonious.In this study,lactic acid bacteria and yeast were used for alcohol fermentation to improve the flavor of apple vinegar,and a high yield acetic acid strain was obtained.Study on brewing technology of apple vinegar with high level of lactic acid has important development prospects in apple vinegar production.The main results were as follows:1.Lactobacillus plantarum 14-2-1 was confirmed to the optimum strain through comparative analysis of the lactic acid producing ability and resistance of alcohol.Ethanol fermentation was optimized by the inoculation of yeast,Lactobacillus plantarum 14-2-1 and temperature.Results indicated that when it was added with yeast 1‰,Lactobacillus plantarum 14-2-1 20%,temperature at 30℃,the alcoholic concentration could reach 11.0%vol,lactic acid content 9.21 g/L.With subsequent addition of concentrated juice,high lactic acid cider(15.5%vol,total acid 13.82 g/L)can provide a lactic acid-rich raw materials for the brewing of apple vinegar,which was 3 times the ordinary cider.2.A high acetate-yielding strain CYD159 was isolated and identified as Acetobacter pasteurianus.The effect of ethanol concentration on acetate formation in feed batch fermentation was also studied.The optimal parameters were obtained as follows: the initial ethanol concentration was 3%vol,the flow feed rate was adjusted to keep alcohol less than 3%vol and segmentation was carried out at 36 h、66 h and 85 h,respectively.Under these conditions,total acidity of apple vinegar reached to 120 g/L,which was twice the total acidity concentration of batch fermentation.3.L.plantarum 14-2-1 and A.pasteurianus CYD159 were applied to the fermentation of high acid apple vinegar with optimized process.Organic acid,the major flavors,and physical and chemical indexes of the fermented vinegar were analyzed.The results showed that the lactic acid content of cider and apple vinegar was about 9.27 g/L higher than that of the control.The content of ethyl lactate was also increased by 45.26 mg/L with the control not detected.The contents of ethyl acetate and ethylhexanoate were increased,the total amount of ester compounds(79.25 mg/L)was about 3 times compared with the control.Physical and chemical indicators were equal to the control,except for total acidity.In summary,ethanol fermentation with L.plantarum 14-2-1 can improve the non-volatile acid content in apple cider vinegar,weaken the irritation of apple vinegar and make the flavor abundant.A.pasteurianus CYD159 has a strong capacity of acid production for acetic acid fermentation,which can improve the acidity of apple vinegar.This study can provide the reference value for the production of apple vinegar with high acidity.