Management Of Acetaldehyde And Other So2 Binding Compounds To Reduce Sulfite Dependency During Vinification

摘要

The potency of SO2 is highest when it is in a free or unbound state. High concentrations of SO2 binders in wine may greatly diminish the efficacy of SO2. The decreased preservative efficacy of bound SO2 requires increased SO2 additions to wine for adequate preservation action. However, additional sulfite concentrations may increase the risk of adverse health reactions for sensitive consumers and may also exceed legal limits for SO2 in wines. Hence, this work investigated important SO2 binding compounds throughout vinification and developed strategies for their control to increase the preservative efficacy of SO2 and limit total additions to wine. Comprehensive analysis of SO2 binding compounds at practical concentrations was achieved through the development of a novel UHPLC method that used the metal chelator, EDTA, to limit oxidation reactions during sample preparation. This method greatly improved existing protocols limited by complex sampling procedures and long HPLC analysis times. A survey of 237 wines from across NYS showed clear differences in the SO2 binder profiles between different wine types. Red wines were typically higher in [alpha]ketoglutaric acid and galacturonic acid, whereas, white wines were higher in acetaldehyde, pyruvic acid and glucose. Major regulating factors for acetaldehyde production during alcoholic fermentation were SO2 addition prior to inoculation, fermentation temperature and grape must type. With the exception of galacturonic acid, the concentrations of acetaldehyde, pyruvic acid and [alpha]-ketoglutaric acid decreased following inoculation with O. oeni. Overall bound SO2 levels were decreased by 22% during MLF and an additional 53% one week later. During MLF, acetaldehyde bound SO2 increased mean O. oeni lag times in a dose dependant manner. Metabolism of bound SO2 by O. oeni resulted in concomitant increases in free SO2 concentrations, which never rose about 8.0 mg l-1. Malic acid was depleted by O. oeni, despite the presence of acetaldehyde bound SO2. Findings suggest that significant reductions in SO2 binders can be achieved by both yeast and bacterial metabolism during vinification. However, O. oeni growth may be limited by the presence of excessive bound SO2 concentrations. To decrease acetaldehyde levels during cellaring, oxygen ingress should be completely restricted.