Application Of Natural Antimicrobial Agents In Wine Brewing

Bacterial contamination is an important problem in wine brewing.Antibacterial agents are often used to inhibit bacterial growth and metabolism for wine quality.SO2 is usually used as antibacterial agent in wine brewing.However,SO2 is harmful to people's health.In this paper,the effects of onion and aloe as antimicrobial agent on the fermentation and quality of wine were studied.The antibacterial effect of 2%-8%addition of onion and aloe were compared with that of 50 mg/LSO2 in wine fermentation.The results showed that the greater the concentration of onion or aloe,the stronger the inhibition to bacteria and mold.the antibacterial effect of 5%onion was equivalent to that of SO2.The antibacterial effect of aloe was weaker than onion at the same concentration,and was even less than SO2.Unlike SO2,5%or 8%addition of onion and aloe could inhibit the endogenous Saccharomyces cerevisiae.the greater the concentration,the stronger the inhibition.The antibacterial effect of 5%onion and 8%aloe in different fermentation and effect on wine quality were studied.The results showed that whether inoculated fermentation or spontaneous fermentation,onion,aloe and SO2 wouldn't affect the final pH value,total acids and ethanol content,reduced the redox potential on the same level.Onion could reduce browning degree the greatest,followed by aloe,SO2 the least.Unlike SO2,onion and aloe would reduce wine color intensity and increase volatile acids.The antibacterial effect of SO:,onion and aloe in spontaneous fermentation were better than that of inoculated fermentation.They could slow down sugar consumption and metabolites production in spontaneous fermentation.SO2 would significantly increase isoamyl alcohol but reduce total higher alcohols,n-propyl alcohol,ethyl acetate and total esters in wine,the effect of aloe was opposite to that of SO2,onion would reduce isoamyl alcohol and total higher alcohols.Compared with the control,onion,aloe and SO2 wouldn't affect total esters.Onion would increase propyl alcohol and total higher alcohols,aloe would reduce isoamy alcohol and total higher alcohols,while SO2 didn't affect higher alcohol content.Compared with spontaneous fermentation,inoculated fermentation could accelerate sugar consumption and metabolites production,increase color intensity,browning degree,total acids,isoamyl alcohol and total higher alcohols,decrease the pH value,volatile acids,propyl alcohol and total esters,but wouldn't affect the redox potential and ethanol content of wine.Onion and aloe could inhibit bacterias,molds and yeasts in wine fermentation system,the greater the concentration,the stronger the inhibition.They could be used together with SO2 in wine brewing to decrease SO2 addition and improve the safety of wine.The antimicrobial effect of onion was stronger than of aloe.They could increase the positive flavor contents and decrease the the negative flavor contents.Aloe could promote the flavor of wine better and without any foreign taste.Addition of onion wouldn't produce significant foreign taste and flavor.