Oenological tannins to prevent Botrytis cinerea damage: reduction of laccase activity

Abstract

Oenological tannins are classified as hydrolysable and condensed tannins. Their use in winemaking is only authorized, to facilitate wine fining. Nevertheless, tannins could also be used to prevent laccase effects. 

Indeed, our group has recently proved their effects against laccase damage [1]. The goal of this study was to better understand the mechanism of action of oenological tannins on laccase activity induced by Botrytis cinerea. Five oenological tannins were used (gallotannin, ellagitannin, quebracho, grape-skin and grape-seed) and compared with ascorbic acid (AA) and sulfur dioxide (SO2). Oenological tannins, AA and SO2 were added to botrytized must at different doses. After 4 minutes, laccase activity was measured by the syringaldazine method [2] using different concentration of subtract. Enzymatic kinetic constants (Km/Vmax) were determined according to Michaelis-Menten model. Furthermore, B. cinerea (strain 213) was grown in a stimulating liquid medium for laccase production [3]. The molecular weight (MW) and the effect of bentonite and tannins upon laccase were studied by SDS-PAGE. The results confirm that all oenological tannins inhibit laccase activity and that the higher the dose the lower the laccase activity. In this way, gallotannin, grape-seed and skins tannins seem to be the most effective tannins. All the tannins were as effective as AA, even though SO2 was clearly the most effective inhibitor. The laccase produced by B. cinerea had a MW of 95 kDa. After bentonite treatment all wine protein bands disappeared and laccase band decreased slightly although its activity remains stable. The interaction between different oenological tannins and laccase was analyzed by measuring the reduction of the intensity of the laccase band. In general, the reduction of band intensity correlates with the reduction of laccase enzymatic activity. 

It can be concluded therefore that oenological tannins a good candidate to prevent laccase effects, helping to diminish the SO2 dose in grapes infected by B. cinerea. 

[1] Vignault, A.; Pascual, O.; Jourdes, M.; Moine, V.; Fermaud, M.; Roudet, J.; Canals, J.M.; Teissedre, P-L.; Zamora, F. Oeno One, 2019. 
[2] Urbano Cuadrado, M.; Pérez-Juan, P.M.; Luque de Castro, M.; Gomez-Nieto, M.A., Anal Chim Acta, 2005, 553, 99-104. 
[3] Quijada-Morin, N.; Garcia, F.; Lambert, K.; Walker, A.S.; Tiers, L.; Viaud, M.; Sauvage, F-X.; Hirtz, C.; Saucier, C.; Aust J Grape Wine Res, 2018, 24, 241-251.