Use of Lysozyme and Oligomeric Proanthocyanidin to Reduce Sulfur Dioxide and the Evolution of Volatile Compounds in Italian Riesling Ice Wine During Aging Process

Abstract

In order to reduce sulfur dioxide (SO2) level in ice wine making, the effects of low SO2, lysozyme and oligomeric proanthocyanidin (OPC) on the volatile compounds were, respectively, studied during 1 year aging process. Based on the previous study, seven treatments of Italian Riesling ice wine were carried out for monitoring the evolution of volatile compounds. Results of gas chromatography mass spectrometry (GC-MS) showed that, about 180 mg/L SO2 not only increased total alcohols content in Italian Riesling ice wine, but also significantly correlated with certain higher alcohols during 1 year aging process. Meanwhile, the final concentration of medium-chain fatty acid ethyl esters and the corresponding fatty acids were found highly related to lysozyme adding. Moreover, OPC played a positive role in stabilizing the total content of esters at a level around 200 mg/L, it mainly due to its excellent ability of free oxygen scavenging. Finally, principal components analysis (PCA) was conducted to reclassify major volatile compounds and 14 typical volatile components were defined. Practical Application This article was technically supported by our previous research: Development of lysozyme-combined antibacterial system to reduce sulfur dioxide and to stabilize Italian Riesling ice wine during aging process and mainly studied three volatile compounds evolution (alcohols, acids and esters) in Italian Riesling ice wine during 1 year aging process. It not only illustrated SO2 can not be totally replaced after alcohol fermentation because of its extraordinary contribution on alcohols and esters composition, but also indicated an appropriate range of SO2 addition (180–200 mg/L) contributes to the synthesis of fruity and floral bouquet for aging. On the other hand, the addition of lysozyme and OPC not only improved the activity of LAB inhibition and antioxidant for ice wine aging, but also promoted certain esters evolution, which contributed more complexities for ice wine bouquet. It further proved the utilization of our system can be very promising and beneficial for reducing SO2 concentration and stabilizing Italian Riesling ice wine during aging process.