The impact of wine closure and packaging type, and light and temperature exposure on the concentration of 3-alkyl-2 -methoxypyrazines and other key constituents of wine

摘要

3-alkyl-2-methoxypyrazines (MPs) are grape- and insect-derived odor-active compoundsresponsible for vegetative percepts that are detrimental to wine quality when elevated. This studytested both the effect of closure/packaging types and light/temperature storage conditions onMPs (isopropyl-, secbutyl-, and isobutyl-MP) in wine. An MP-emiched wine rapidly (after 140hours) and significantly decreased in MP concentration after natural and synthetic cork contact(immersion of closures in wine). This decrease was greatest with synthetic closures (70% - 89%reduction) and secbutyl-MP. Subsequently storage trials tested the effects of commercialclosure/packaging options (natural cork, agglomerate cork, synthetic corks, screwcaps andTetraPak® cartons) on MPs in MP-emiched Riesling and Cabernet Franc over 18 months.Regardless of packaging, isobutyl-MP was the most altered from bottling. Notably, all MP levelstended to decrease to the greatest extent in TetraPak® cartons (~34% for all MPs) and there wasevidence of contribution ofisoproyl- and secbutyl-MP from cork-based closures (i.e. ~30%increase in secbutyl-MP after 6 months) or from an unidentified wine constituent. To test theeffects of various light/temperature conditions (light exposed at ambient temperature in threedifferent bottle hues, light excluded at ambient temperature and light excluded at a "cellar"temperature (14°C)), MP-emiched Riesling and Cabernet Franc were also analyzed for MPconcentrations over 12 months. MPs did not vary consistently with light or temperature. Otherodorants and physico-chemical properties were tested in all wines during storage trials andclosely agree with previous literature. These results provide novel insights into MPs duringageing, interactions with packaging and storage conditions, and assist in the selection of storageconditions/packaging for optimal wine quality.