An official website of the United States government.
This project will address one of the most frequently encountered problems in the NY wine industry; unintended oxidation. Besides measuring acetaldehyde in finished and bottled wines in the first project year, and comparing the values obtained to other key wine parameters, the project will also study the concentration of acetaldehyde in samples taken along the grape handling and wine processing chain in the following years. This will allow us to identify processes that have key significance for causing oxidations and thus, increasing acetaldehyde levels. Data from both study parts will allow us to 1) assist wineries that have identified oxidation problems based on the survey and 2) target our extension efforts towards critical steps identified in the second study part. Objective 1. Acetaldehyde and other key wine parameters in New York State wines. Acetaldehyde levels in wines from New York State wineries will be measured and correlated with other key grape and wine quality parameters (VA, TA, RS, free, total SO2). The minimum target will be 100-120 wine samples provided by 30-40 wineries across New York State with several wine types spanning red, white, dry and sweet wines. Objective 2. Course of acetaldehyde concentrations along the grape handling and winemaking process. Data gained from Objective 1 will be used to identify wineries with low and high acetaldehyde levels. The course of acetaldehyde concentrations in selected wineries with high and low levels will then be studied over a two year period in order to consider annual variations and, in the last project year, to assess the overall reduction of acetaldehyde levels following technology transfer. Measuring acetaldehyde in samples taken at various time points of the grape handling and vinification process will allow us to identify critical points that increase acetaldehyde concentrations and should be targeted for specific extension efforts.
NON-TECHNICAL SUMMARY: Wineries in New York State are very different with regards to the professional background of their employees. Personnel with a traditional background in winemaking can be found next to oenologists with a formal education, but also winemakers without any formal education and little practical experience. This tends to be reflected in an equally differentiated product spectrum. Wines with sensory defects appear to be more frequent and can significantly impede the economical development of individual wineries as well as having a negative effect on the overall appreciation of NYS as a premium quality winemaking region. This project will address one of the most frequently encountered problems, which is also generally independent from individual preference, i.e. unintended oxidation. Acetaldehyde is an excellent indicator for oxidations that have occurred during the winemaking or wine storage and packaging process. Thus, we propose to measure this compound to survey the occurrence of unintended oxidations in the wine industry. Acetaldehyde also binds to the wine preservative SO2, which has to be compensated by increased SO2 additions in oxidized wines. Considering the adverse reactions of sensitive consumers to SO2 controlling oxydation in wines, thus, also is of food safety relevance.
<p>
APPROACH: This project will commence with a survey of acetaldehyde in New York wines. Acetaldehyde levels in wines from New York State wineries will be measured and correlated with other key grape and wine quality parameters (volatile acidity, total acidity, residual sugar, free and total SO2). The minimum target will be 100-120 wine samples provided by 30-40 wineries across New York State with several wine types spanning red, white, dry and sweet wines. In addition to measuring acetaldehyde in finished and bottled wines in the first project year, and comparing the values obtained to other key wine parameters, the project will also study the concentration of acetaldehyde in samples taken along the grape handling and wine processing chain in the following years. Data gained from Objective 1 will be used to identify wineries with low and high acetaldehyde levels. The course of acetaldehyde concentrations in selected wineries with high and low levels will then be studied over a two year period in order to consider annual variations and, in the last project year, to assess the overall reduction of acetaldehyde levels following technology transfer. Measuring acetaldehyde in samples taken at various time points of the grape handling and vinification process will allow to identify critical points that increase acetaldehyde concentrations and should be targeted for specific extension efforts. All samples will be handled under inert gas cover and analyzed by a specific enzymatic analysis developed in the laboratory of the applicant, which is validated against a GCMS method. The method is a standard enzymatic end-point method relying on the reduction of NAD to NADH, which can be followed by spectrophotometry at 340 nm. Reagent concentrations have been optimized to allow a large dynamic range of 0-150 mg/l of acetaldehyde using a second degree polynomial regression based on data from external standards. Further analytical values obtained for every wine will be the free and total SO2 (by flow injection analysis, Foss FIA Star), and total and volatile acidities, residual sugars, and the concentrations of alcohol and organic acids, specifically L-malic and lactic acids (by FTIR, Foss WineScan). Data thus obtained will be evaluated for correlations between acetaldehyde and other key wine parameters using a statistical software package (SPSS v14), graphically represented (Originlab 7.0 software) and published online and in print media. All wine samples will be coded and wineries will only be able to identify their own wines, while still being able to compare their values with wines from other (anonymous) producers.