Yeast-Bacterial Interactions during Malolactic Inoculations Affecting Anthocyanin Adsorption and Content in Shiraz Wine

Wine color is an important sensory attribute originating from anthocyanins present in grape skin. The present study investigated the involvement or interference of bacterial cells (Oenococcus oeni and Lactobacillus plantarum mixed culture) on the adsorption of Shiraz anthocyanins during co-inoculation with yeast. The yeast-bacterial interactions during co-malolactic fermentation resulted in higher levels of glucosides and vitisin B and lower levels of coumaryl and caffeyl anthocyanins compared to wines produced via sequential malolactic fermentation and alcoholic fermentation. However, a detailed profiling of the sediments (lees) revealed no significant differences in the anthocyanin adsorption patterns between alcoholic- and malolactic-fermentation inoculations, even though significant differences were observed in the wines. The lees primarily contained acylated anthocyanins of peonidin and malvidin, indicating hydrophobic interactions involved in adsorption. Overall, yeast-bacterial interaction during malolactic fermentation showed a drastic influence on the final wine composition, and adsorption was a minor variable governing the anthocyanin changes. The incorporation of the L. plantarum strain for co-inoculation resulted in high pyranoanthocyanin levels and could therefore be a strategy to prevent loss of color during co-inoculation.