Approaches to prevent the light-struck taste in white wine

Background and Aims: The light-struck taste is a fault occurring in light-exposed white wine containing methionine and a high concentration of riboflavin (RF) and bottled in clear bottles. These conditions induce the formation of methanethiol and dimethyl disulfide, responsible for a cabbage-like aroma. In order to decrease the risk of wine spoilage, a low concentration of RF should be obtained in wine either by preventing RF release from yeast during winemaking or by removing RF from wine. Methods and Results: Fifteen commercial Saccharomyces strains intended for the wine industry were tested for RF production which was also evaluated when two yeast-based nutrients were added into the must for one of these strains. The RF released during vinification was strain-dependent and a concentration from 30 to 170 g/L was found in wine. A high concentration of RF was released in presence of the yeast-based nutrients due to either the yeast metabolism or the RF contained in the nutrient itself. The ability of different inorganic (bentonite, charcoal, zeolite, kaolin) and organic adjuvants (egg-white proteins, polyvinylpolypyrrolidone) to deplete RF in wine was evaluated. A relatively low level of charcoal (50 mg/L) removed up to 60% of RF in wine, though its effectiveness was related to the charcoal source. A high concentration of bentonite (1 g/L) was needed to effectively decrease the risk of wine spoilage. Conclusion: A critical RF concentration in white wine can be prevented by applying one or more approaches in winemaking: using low RF-producing yeast strains in fermentation, selecting suitable yeast nutrients or adsorbing RF by insoluble charcoal or bentonite. Significance of the study: The research highlights suitable tools to prevent light-struck taste in white winemaking.