Influence of addition of assimilable nitrogen on alcoholic fermentation in chemically defined must by wine yeasts | 模拟葡萄汁中添加可同化氮对酵母菌酒精发酵的影响

صينى. 研究添加可同化氮对模拟葡萄汁酒精发酵的影响，确定利于酵母菌酒精发酵的可同化氮水平，为葡萄酒酿造过程中可同化氮的添加提供依据。设计3种氮素添加方式，分析不同质量浓度可同化氮和添加处理下模拟葡萄汁的酒精发酵过程及产物的差异，对各处理酒精发酵过程中的酵母菌数量和还原糖含量及酒精发酵结束后的游离氨基酸、铵态氮、有机酸、香气成分含量进行测定和分析。随着可同化氮质量浓度的升高，酵母菌数量增加，酒精发酵速率增大，二次添加可同化氮使酵母菌数量增加较快，糖消耗速率增大；可同化氮质量浓度为240 mg/L时，有机酸的总生成量最高，二次添加可同化氮降低了有机酸的总生成量，提高了乳酸、乙酸和琥珀酸的生成量，但柠檬酸的生成量有所降低；可同化氮质量浓度的升高有利于生成较多的香气成分，二次添加处理可以提高高级醇和酯类的生成量，但对酸类生成量无明显影响。可同化氮是酵母菌进行正常酒精发酵必需的大量营养元素，可同化氮质量浓度低于90 mg/L时，添加有机氮(氨基酸)和无机氮(铵态氮)均能促进酵母菌完成酒精发酵，可同化氮质量浓度的升高有利于生成较多的香气成分。

إنجليزي. The influence of addition of nitrogen on alcoholic fermentation was studied. Comparing the fermentation products, the good level of nitrogen concentration was found which will provide a basis of additional assimilable nitrogen in brewing process. In this experiment, the chemically defined musts were in different concentrations of assimilable nitrogen fermentated. The results showed that during fermentation the yeast number was growing up as the assimilable nitrogen concentration increased. The fermentation rate and the sugar consumption rate of additional treatments were higher before addition; the total organic acids was the highest with the assimilable nitrogen concentration at 240 mg/L, additional treatment reduced the amount of citric acid and increased the lactic acid, acetic acid and succinic acid; the formation of aroma components benefited from the increasing assimilable nitrogen concentration. The additional treatments improved the formation of higher alcohols and esters, but the effect on the amount of acids was not obvious. The yeast assimilable nitrogen was one of the necessary nutrients for yeasts in alcoholic fermentation. When the content of yeast assimilable nitrogen was at 90 mg/L, addition of amino acids and ammonium promoted the yeast to finish the alcoholic fermentation. The productions of aroma components grew up as the levels of yeast assimilable nitrogen increased.