Using a cysteamine derivatization procedure and analysis with GC-Nitrogen Phosphorous Detection (GC-NPD) volatile, saturated aldehydes (C1-C9) in wine or aqueous ethanol can be accurately measured as their corresponding thiazolidine derivative. Using this procedure we have shown in preliminary experiments, that S02 additions during fermentation can effect the concentrations of a number of aldehydes. Further confirmatory studies are now in progress. We are also validating a separate method for the analysis of unsaturated aldehydes (e.g., acrolein) and dicarbonyls (malonaldehyde) in wines and distillates. The method is based on the reaction of these aldehydes with N-methylhydrazine to form methyl pyrazoline derivatives which can be analyzed by GC-NPD. In preliminary studies, we have obtained a limit of detection of 0.2 mg/mL and a limit of quantification of 0.5 mg/mL for acrolein and malonaldehyde. Spiked recoveries averaged 90 ± 12%for acrolein, malonaldehyde, and crotonaldehyde over a series of concentrations (2-20 mg/mL) in model wine and wine matrices.
Volatile, saturated aldehydes (C1-C9) in wine or aqueous ethanol solutions were derivatized with cysteamine to form the corresponding thiazolidine derivative. Following extraction into chloroform and gas chromatographic analysis, a limit of quantitation of 1 mg/mL was achieved using a nitrogen phosphorous detector. Spiked recoveries in wine were 112% with an overall coefficient of variation of 16%. The derivatization procedure was used to determine aldehyde levels in several wines: acetaldehyde was observed in the highest concentrations in these wines, however, other aldehydes were also often present. During the current year the focus has been on decreasing the variability of the analytical method.
Short chain, volatile aldehydes contribute important sensory properties to wines and can affect aging and color stability. We optimized a derivatization procedure for the quantitative analysis of volatile, saturated aldehydes (CI – C9) in wine. Aldehydes were derivatized with cysteamine to form the corresponding thiazolidine derivative. The derivatives were then extracted into chloroform and analyzed by gas chromatography. Using a nitrogen phosphorous detector, the limit of quantitation was 1 mg/mL with average spiked recoveries in wine of 113% (Coefficient of Variation = 16%). The method was able to show differences in aldehyde levels in wines as a function of grape variety and processing conditions. Although acetaldehyde was observed in the highest concentrations, other aldehydes were also often present.