Effect Of Glutathione On The Quality Characteristics Of Apple Wine And The Growth Of Saccharomyces Cerevisiae

Reduced glutathione（GSH）is a kind of active tripeptide widely present in biological cells,which has important physiological functions.In clinical medicine,GSH was used to improve antioxidation,detoxification and immunity.In the field of food processing,it can also improve food flavor and increase the value of nutrients.Apple wine is a kind of fruit wine with the second annual output,but there are some problems in apple wine making process such as juice oxidation,browning,high organic acids content and aroma loss.In this study,Fuji apples planted in Shaanxi Province were used to make apple wine.GSH of 10,20and 30 mg/L was added respectively before alcoholic fermentation,malolactic fermentation and aging.Meanwhile,Saccharomyces cerevisiae WLP775 and Oenococcus oeni SD-2a that had been pre-incubated with GSH（100 mg/L）were used to start alcoholic fermentation and malolactic fermentation respectively.The effects of GSH on the quality characteristics of apple wine and the growth of S.cerevisiae were evaluated by detecting representative indicators at different stages.The main results are as follows:（1）The addition of GSH effectively inhibited the browning of apple wine during alcoholic fermentation,significantly increased the total phenol content,and changed the characteristics of mono-phenols as well as volatile aromas of apple wine.Among them,30mg/L GSH had the most remarkable effect on inhibiting browning and protecting polyphenols,and 20 mg/L GSH had the best effect on improving aroma.The e-nose could also effectively distinguish the control group from the apple wine with GSH and the apple wine inoculated with S.cerevisiae pre-incubated by GSH.（2）S.cerevisiae WLP775 showed the ability to absorb GSH from culture environment.GSH could promote the growth of S.cerevisiae WLP775 under stressd conditions such as pH,high ethanol content and high SO₂ content.The content of four saturated fatty acids,lauric acid,palmitic acid,stearic acid and arachidic acid,were significantly reduced and their corresponding unsaturated fatty acids content were increased.（3）Adding GSH or inoculating O.oeni SD-2a that was pre-cultured by GSH could accelerate the process of malolactic fermentation and make the apple wine with lower malic acid content and higher lactic acid content.Adding GSH or inoculating GSH pre-cultured O.oeni could also significantly improve the softness index of apple wine after malolactic fermentation,of which 30 mg/L was the most effective.However,the addition of GSH decreased the total phenol content as well as changed the mono-phenols and volatile aromas composition of apple wine after malolactic fermentation.（4）During the aging stage of apple wine,the addition of GSH could not only effectively inhibit the loss of some volatile aromas,such as alcohols,esters,aldehydes,ketones,terpenes and so on,but also significantly reduce the content of acid aromas.The electronic tongue system was effective to distinguish the apple wine with different treatments.In addition,the sensory evaluation of apple wine after ten months of aging was carried out.The apple wine with 20 mg/L GSH addition obtained the highest score,followed by the apple wine with 30 mg/L addition.The results indicated that GSH had a positive and significant effect on the quality characteristics of apple wine in three stages:alcohol fermentation,malolactic fermentation and aging.Moreover,GSH could promote the growth and reproduction of S.cerevisiae WLP775 under stress conditions,which is beneficial for S.cerevisiae to initiate alcoholic fermentation better.The results provide a theoretical basis for the application of GSH as an additive in the apple wine making.