Light-Struck Taste in White Wine: Protective Role of Glutathione, Sulfur Dioxide and Hydrolysable Tannins

Abstract

Light exposure of white wine can cause a light-struck taste (LST), a fault induced by riboflavin (RF) and methionine (Met) leading to the formation of volatile sulfur compounds (VSCs), including methanethiol (MeSH) and dimethyl disulfide (DMDS). The study aimed to investigate the impact of different antioxidants, i.e., sulfur dioxide (SO2), glutathione (GSH) and chestnut tannins (CT), on preventing LST in model wine (MW) and white wine (WW), both containing RF and Met. Both MW and WW samples were added with the antioxidants, either individually or in different combinations, prior to 2-h light exposure and they were stored in the dark for 24 months. As expected, the light induced the degradation of RF in all the conditions assayed. Met also decreased depending on the antioxidants added. The presence of antioxidants limited the formation of LST as lower concentrations of VSCs were found in both MW and WW samples. In the latter matrix, neither MeSH nor DMDS were detected in the presence of CT, while only DMDS was found in WW+GSH, WW+SO2+GSH and WW+CT+SO2 samples at a concentration lower than the perception thresholds. Considering the antioxidants individually, the order of their effectiveness was CT ≥ GSH > SO2 in WW under the adopted experimental conditions. The results indicate tannins as an effective enological tool for preventing LST in white wine and their use will be further investigated in different white wines under industrial scale.

Evaluation of oenological tannins for preventing the light-struck taste

“…In order to exclude any influence on taste and mouthfeel properties, astringency and bitterness perception was evaluated in white wine added up to 80 mg/L of the investigated tannins. As no significant difference was found (data not showed), the adopted addition of tannins was 50 mg/L, also in accordance with a previous research (Fracassetti et al, 2021b).…”

“…This can be due to the oxidation of Met arising to different compounds (Barata-Vallejo et al, 2010), including Met sulfoxide and methionine sulfone. The latter was not detected in any of the sample (data not showed) accordingly to previous studies (Fracassetti et al, 2020b(Fracassetti et al, , 2021b. Met sulfoxide was found in all the samples, either exposed (0.17-0.74 mg/L)…”

“…We are conscious some differences can arise between model wine and white wine in terms of LST intensity. Nonetheless, the effectiveness of tannins, specifically those from chestnut, was found in both model wine and white wine (Fracassetti et al, 2021b). This makes of significance the screening in model wine that allows to understand the possible differences between the tannins tested and to exclude the impact of other wine components into the light-induced mechanisms.…”

“…Hydrolysable tannins have recently proved to limit the formation of LST in model wine (Fracassetti et al, 2019) and white wine (Fracassetti et al, 2021b). Specifically, the tannins from chestnut, nut gall, and oak were investigated.…”

“…Moreover, the chestnut tannin in mixture with sulfur dioxide (SO2) and glutathione (GSH) was recently investigated in both model wine and white wine. The effectiveness of hydrolysable tannins in preventing LST was highlighted also when hydrolysable tannins were combined use of other antioxidants (i.e., SO2+GSH) (Fracassetti et al, 2021b).…”