Parameter optimization aroma enhancement fermentation technology of dry white wine

Aroma is one of the important parameters for evaluating wine quality. With respect to there origin, wine aroma components can be classified into three groups: they are derived from grape fruits, fermentation and maturation process. Although several factors may play a role in the aroma quality of wine, the fermentation condition is possibly the most important element. In this study we investigated the impact of single and complex fermenting factors on the main aroma compounds of Italian Riesling Dry White Wine. The volatile flavor compounds in grape wine samples treated with different content of assimilable nitrogen (200, 300, 400 mg/L), yeast polysaccharides (150, 250, 350 mg/L), fermentation temperature (14, 18, 22℃), initial pH (3.3, 3.5, 3.7) and SO2 addition (40, 70, 100 mg/L) were detected by headspace solid phase microextraction/gas chromatography-mass spectrometry. A large effect of fermentation condition on wine aroma quality was observed. The results showed that 300 mg/L of assimilable nitrogen was beneficial to the accumulation of higher alcohols, esters and monoterpenoids in wine samples. When yeast polysaccharides were added at 250 mg/L, the content of monoterpenoids reached the maximum (198.54 μg/L). With the increase of fermentation temperature from 14℃ to 22℃, the content of higher alcohols increased significantly, while the content of esters and monoterpenes decreased significantly. Increasing the initial pH of grape juice was beneficial to the accumulation of monoterpenoids, among which linalool and geraniol changed most significantly, but it was not conducive to the formation of higher alcohols and esters. Increased concentration of higher alcohols were detected, while ester aroma components and monoterpenoids content were differentially modulated by SO2 addition increased from 40 mg/L to 100 mg/L, andwhen SO2 content was 70 mg/L, the total content of monoterpenes was the highest (181.73 μg/L). The range analysis of orthogonal design carried out on wine samples collected from eight experimental groups indicated that fermentation condition affected the formation of the main aroma compounds. The contents of B6 (ethyl caprate), B5 (etheyl octanoate) and C1 (linalool) varied greatly among different treatments, while the contents of A1 (1-hexanol) and B3 (phenylethyl acetate) changed slightly among different wine samples. In addition, the total amount of ester compounds differed greatly among different experimental groups, the content of monoterpenoids and higher alcohols differed slightly. Fermentation temperature and the amount of SO2 added had a great influence on the concentration of higher alcohols, fermentation temperature and assimilable nitrogen had a great effect on the content of ester aroma compounds, and the contents of monoterpenes were significantly regulated by yeast polysaccharide and initial pH. The clustering results showed that the correlation between assimilable nitrogen and yeast polysaccharide on the main aroma compounds in wine samples was high, and the correlation between the initial pH of grape juice and the addition of SO2 was high. The lower fermentation temperature (18℃) was conducive to the formation of geraniol, isopentanol, 2-phenylethyl alcohol and etheyl octanoate. Adding medium concentration of assimilable nitrogen (300 mg/L) and yeast polysaccharide (250 mg/L) could promote the synthesis of isopentyl acetate, hexyl acetate and ethyl caproate. Higher initial pH was conducive to the accumulation of linalool, citronellol and geraniol. Moreover, the physical and chemical indexes of all wine samples meet the requirements of national standards. Our study reveals that the synthesis and release of main aroma compounds in Italian Riesling Dry White Wine can be effectively promoted by the production conditions of fermentation temperature 18℃, initial pH value 3.5, the amount of SO2 added to 70mg/L, assimilated nitrogen 300 mg/L and yeast polysaccharide 250 mg/L. © 2019, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.