The Contribution Of Mono- And Diglucosidic Anthocyanins To Red Wine Color
Non-vinifera grapes and wines, including interspecific hybrids, have unique anthocyanin and color profiles, most notably high concentrations of anthocyanin diglucosides. While there are many studies on the anthocyanin profiles and color composition of traditional European Vitis vinifera grapes and wine, there are few studies on non-vinifera grapes and wines. Red wine color is an important quality parameter for consumers, who associate deeper color with higher quality. Anecdotal evidence suggests that the color of red hybrid wines is unstable, and does not undergo the transition to a brick-red color upon aging like V. vinifera wines. In this study, the individual reaction kinetics of the conversion of monomeric anthocyanin mono- and diglucosides to polymeric pigment (stable color) in the presence of acetaldehyde were measured using high performance liquid chromatography (HPLC). The impact of anthocyanin competition, or a more complex matrix, on reaction kinetics was measured by preparing reactions that contained both the mono- and diglucosidic forms of each anthocyanidin base. Changes in color that occurred as a result of chemical reactivity were recorded with colorimetry. It was found that anthocyanin diglucosides react significantly slower than monoglucosides, indicating slower formation of polymeric pigment and less stable color. When the mono- and diglucosidic forms of one anthocyanidin base were placed in competition with each other, the rate of the monoglucosides decreased significantly, indicating that the competition of the diglucosides impacted the reaction rates of the monoglucosides. In each trial, the color either remained red, or transitioned from red to red-orange or orange. These results indicate that non-vinifera and hybrid wines containing high concentrations of anthocyanin diglucosides are likely to have less polymeric pigment formation over time compared to V. vinifera wines that contain only monoglucosides. This lack of polymeric pigment will significantly affect the color and acceptability of hybrid wines. Because there are few studies on the compositions of hybrid grapes and wines, a second study was completed to provide further analytical information on five interspecific hybrid grape cultivars: Frontenac, La Crescent, Marquette, MN 1200, and St. Croix. Anthocyanin concentration was measured via HPLC, protein concentration with a modified version of the Amido Black protein assay, and tannins with the Adams-Harbertson assay. Hybrid grapes were found to contain relatively high levels of total anthocyanins, and anthocyanin profiles were dominated by diglucosides, which impacts the ability to form polymeric pigment. Protein concentrations were found to be lower than in other studies on hybrid grapes, while tannin concentration was similar to that found in the scientific literature and lower than that of V. vinifera wines; low tannin concentrations also impact the formation of polymeric pigment. This information will give winemakers using hybrid grapes baseline measurements, which will allow them to choose processing methods to reach desired wine composition.
Anthocyanin; Hybrid wine; Wine color
Food Science and Technology
M.S., Food Science and Technology
Master of Science
dissertation or thesis