Preparation Of Selenium Enriched Active Yeast And Its Effect On Mulberry Wine Fermentation

Mulberry is rich in nutrients and has many health benefits.It is considered as a kind of "medicine food homology" small berry by the ministry of health of China.Mulberry wine is a fruit wine made from mulberry by alcohol fermentation which has a bright color and unique flavor.In addition,most of the nutrients of mulberry can be effectively preserved after fermentation.Hence,mulberry wine has a broad development prospect.Selenium has numerous physiological functions.The study aimed at increasing the content of selenium in mulberry wine.In this study,using CECA Saccharomyces cerevisiae,the yeast was firstly enriched with selenium and the best process was optimize.Secondly,the commercially available selenium-enriched yeast nutritional additives were extracted by breaking the wall to obtain lyophilized powder.Finally,the effects of selenium-enriched active yeast,selenium-enriched yeast nutritional additives and extracts,L-se-methylselenocysteine on the quality of mulberry wine were investigated,which provided a theoretical basis for the development of selenium-enriched mulberry wine.The main research contents and results were as follows:(1)Taking selenium content as the index,the effect of different adding times of inorganic selenium on the selenium content of selenium-enriched yeast was investigated.In addition,the optimal adding time of selenium was determined as 4 h.Afterwards,the regression model between Se content and selenium-enriched parameters was established by response surface analysis.According to the practical feasibility,the selenium-enriched time was 58 h,the amount of inorganic selenium was40 μg/m L and the inoculation amount of seed liquid was 4.60%.(2)The wall breaking efficiency of ultrasonic,enzymatic hydrolysis,freeze-thaw,and autolysis methods for selenium-enriched yeast nutrient additives were compared.The result showed that enzymatic hydrolysis method was determined as the best method.Correspondingly,the response surface analysis method was used to optimize the wall breaking process,and a mathematical model was builded.The enzymatic hydrolysis temperature obtained was 54℃,the enzyme dosage was 0.32%,and the seleniumenriched yeast nutrient additive concentration was 4.50%.(3)The total acid and alcohol content of mulberry wine(MW2)fermented by selenium-enriched active yeast were the highest.Besides,the soluble solid was the lowest.The CI,Re%,total polyphenol,total flavonoid,and total anthocyanin content of MW2 and mulberry wine(MW5)during the fermentation were significantly higher than the control mulberry wine(MW1).Also,DPPH scavenging ability,ABTS scavenging ability,hydroxyl radical scavenging ability,and reducing power of those two groups(MW2 and MW5)were significantly increased(p < 0.05).Further,the growth rate of MW5 in polyphenols and anthocyanins was 36.89% and 26.72%respectively.The selenium content of MW8(mulberry wine with L-Se MC after fermentation)was the highest.Nevertheless,the effect of improving oxidation resistance was less.The correlation between selenium content and total flavonoid content was 0.996.Each group of mulberry wine was sensitive to W5 S,W1S,and W2 S sensors of E-nose,and MW2 was the most responsive to W2 S.The alcohol and ester in volatile substances greatly contributed to the aroma of mulberry wine.The quantity(36kinds)and relative percentage of ester were the largest.In addition,the change range of the relative percentage was 60.96?79.90%.Finally,the principal component analysis model was established to evaluate the comprehensive quality of mulberry wine in each group found MW2 was the best quality and consistent with sensory evaluation.