Study On The Influence Of Different Brewing Factors On Volatile Aroma Compounds In ’Italian Riesling’ Dry White Wine

Aroma is a key index to evaluate the style and typicality of dry white wine,and it is mainly affected by yeast species,wine making technology,fermentation conditions and other factors.On the basis of optimizing and comparing the aroma-producing performance of four commercial Saccharomyces cerevisiae strains,this paper discussed the influence and its changing rules of different maceration processes,single and complex fermentation conditions on the main volatile aroma compounds in Italian Riesling dry white wine through micro-fermenting experiments.The main research results are as follows:1.The fermentation kinetics and volatile aroma compounds of four commercial Saccharomyces cerevisiae strains were compared in this experiment.The results showed that the total amount of ester aroma compounds synthesized by LA-FR strain was 1377.63μg/L,which was significantly higher than other strains（p<0.05）,and the aroma-producing performance of LA-FR strain was the most excellent.Moreover,monoterpenes,such as citronellol,geraniol and linalool-were also detected in the simulated wine,which confirmed that Saccharomyces cerevisiae can synthesize the monoterpenes.2.Compared with the traditional process,the low temperature（10℃）maceration process can increase the content of aroma substances in wine.Furthermore,6 higher alcohols,7 esters and 4 monoterpenes were identified as the main aroma compounds of’Italian Riesling’dry white wine by principal component analysis.3.Results of single factor experiments with different fermentation conditions showed that assimilable nitrogen can significantly influence the total amount of alcohols,esters and monoterpenes,and the influence of assimilable nitrogen on fermentation aroma was greater than varietal aroma.The content of monoterpenes reached the maximum value when yeast polysaccharides were added at 250 mg/L;When the fermentation temperature increased from 14℃to 22℃,the content of higher alcohols increased significantly,while the ester and monoterpenes content decreased significantly.With the increase of initial pH value of grape juice,the total amount of higher alcohols and esters decreased,while the content of monoterpenes increased significantly.With the increase of SO₂ concentration,the total amount of higher alcohol compounds increased,while the content of esters decreased,and the monoterpenes increased firstly and then decreased.4.The results of complex fermentation conditions showed that the order of influence on the content of higher alcohols among fermentation conditions was fermentation temperature>SO₂ addition>yeast polysaccharide>assimilable nitrogen>pH;The order of influence on the content of esters was fermentation temperature>assimilable nitrogen>SO₂ addition>yeast polysaccharide>pH;The order of effect on the content of monoterpenes was yeast polysaccharide>fermentation temperature>pH>assimilable nitrogen>SO₂ addition.The results of this study can provide theoretical basis for qualitative modification and precise regulation of aroma quality of Italian Riesling dry white wine.