固定化Saccharomyces cerevisiae HP01 與 Saccharomyces boulardii HS13 在紅葡萄酒發酵之研究

Abstract

本研究利用自黑后葡萄中篩選出之二株釀酒酵母：Saccharomyces cerevisiae HP01及Saccharomyces boulardii HS13，探討此二株酵母菌經固定化後，對紅酒釀製之發酵特性、重複批式發酵能力及其貯存活性之影響。結果顯示，將酵母菌體懸浮於3% 褐藻酸鈉溶液中，以0.2 M CaCl2為凝膠劑，製得固定化酵母菌數達107 CFU/g；之後分別接種游離或固定化酵母於25°Brix之黑后葡萄酒醪中，起始菌數為106 CFU/mL，經25℃發酵16天，所得紅酒成品間之成分分析無顯著差異（p > 0.05）：酒精產量均高於12% (v/v)；還原糖0.31%；總糖0.36-0.41%；總酸度0.89-0.93 %；pH 值3.5-3.6；可滴定酸含量9.1-9.8g/L。利用固定化酵母釀造之紅酒，其揮發性酸產量及短鏈脂肪酸含量較高；而使用游離酵母釀造之紅酒，其總酚含量和高級醇類含量較高。此外，固定化酵母經8批次重複共128天發酵後，仍能保持良好的發酵能力，酒精產量可維持在 13% (v/v) 以上。貯存性試驗結果顯示，固定化酵母於4℃儲存六個月仍有良好發酵能力，菌數維持在107 CFU/g以上，酒精產量高於13% (v/v)。在喜好性品評結果方面，不論是利用游離或固定化酵母所發酵之紅酒，其色澤、風味及整體接受度並無顯著差異；香氣則以固定化酵母所發酵製得之紅酒較佳。

In the previous years, we successfully selected two yeast strains, Saccharomyces cerevisiae HP01 and Saccharomyces boulardii HS13, from Black Queen grapes. Therefore, in this investigation, live yeasts were entrapped in calcium alginate gel beads via dripping the 3% sodium alginate-yeasts suspension into 0.2 M calcium chloride solution. The grape musts were adjusted with sucrose to 25oBrix, followed by inoculation with 106 CFU/mL free or immobilized yeasts. After fermentation at 25℃ for 16 days, fermentation properties such as ethanol yields＞12% (v/v), 0.31% of reducing sugar, 0.36-0.41% of total sugar, 0.89-0.93% of total acidity, 3.5-3.6 of pH, and 9.1-9.8g/L of titratable acidity were not significantly different. The concentrations of volatile acidity and short chain fatty acids were higher in immobilized yeasts, but the concentrations of total pigment content and higher alcohols were higher in free ones. During the recycle batch fermentation, the immobilized yeasts maintained high fermentation activity for more than 8 batches and kept 13% (v/v) ethanol productivity. The viability and fermentation activity of immobilized yeasts didn’t decrease while storage at 4℃ for 6 months. Sensory evaluation showed that color, taste and overall acceptance of red wines made by free or immobilized yeasts were not significantly different. However, the flavor was better for red wines fermentation with immobilized yeasts.