Kinetic Of The Change Of Flavonoid And Polysaccharide Content During The Fermentation Of Lycium Barbarum L. Wine And Optimization Of The Fermentation Conditions

Lycium chinense is a famous fruit has been traditionally used both as food and medicine in China. The berry of Lycium chinense is rich in functional components, mainly flavonoid, and Lycium Barbarum polysaccharides (LBP). Wine of Lycium barbarum L. was supposed to keep the main functional components in the berries, since dipping the berries in alcohol is a widely accepted way to use the berry in Chinese herbal medicine. In order to produce high active components content wine, influence of the fermentation conditions on the results was studied and optimized. Four factors of fermentation temperature, yeast inoculum size, sugar concentration and pH were investigated. Box-Behnken design and Response Surface Methodology (RSM) were used to arrange the experiments and data analysis. The mainly obtained results were listed as the following,(1) During the fermentation, pH value decreased slightly at the first stage and then kept at a stable level until the end. The total flavonoid content kept increasing to a peak value and then changed slightly, similar to of the variation trend of alcohol content. The polysaccharide content (LBP) increased firstly and then declined to a minimum value. Quadratic regression models were developed to show the change of flavoniod content, polysaccharide content and alcohol concentration, respectively.(2) According the RSM analysis on the data of Box-Behnken design, the optimal fermentation conditions for the highest flavoniod content in Lycium Barbarum L. wine were set at fermentation temperature of 21.9℃, yeast inoculum size of 0.29g/L, sugar content of 220.0 g/L and pH 4.3. Under the optimal conditions, flavoniod content in the wine could reach to the highest value of 0.2404 g/L predicted by the model and 0.2337±0.0043 g/L in the real verification test. The constructed model showed good fitness to the experimental data.(3) According the RSM analysis on the data of Box-Behnken design, the optimal fermentation conditions for the highest polysaccharide content in Lycium Barbarum L. wine were fermentation temperature of 21.9℃, yeast inoculum size of 0.31 g/L, sugar content of 297.3 g/L and pH 3.8. Under the optimal conditions, the highest polysaccharide content was predicted as 0.2404 g/L and 0.2337±0.0043 g/L in the verification test.(4) According to the GC/MS analysis, 31 components were identified in the aroma of Lycium Barbarum L. wine. The important aroma components were identified as ester, alcohol, organic acid, ketone and small amount of other components. Seven kind of components, including octanoic acid ethyl ester, hexanoic acid ethyl ester, ethyl acetate, decanoic acid ethyl ester, acetic acid 2-phenylethyl ester, phenylethyl alcohol and octanoic acid, showed relatively higher content among the aroma components, and were supposed as the main arome components in Lycium Barbarum L. wine.