Resumen de Influence of oxygen availability during skin-contact maceration on the formation of precursors of 3-mercaptohexan-1-ol in Müller-Thurgau and Sauvignon Blanc grapes
Roberto Larcher, Giorgio Nicolini, Loris Tonidandel, Tomas Roman, Mario Malacarne, Bruno Fedrizzi
Background and Aims Grape maceration plays an important role in the formation of precursors of 3-mercaptohexan-1-ol (3MH), 3-S-glutathionyl mercaptohexan-1-ol (GSH-3MH) and 3-S-cysteinyl mercaptohexan-1-ol (Cys-3MH), but its contribution is still not well understood. The aim of this paper was to study the effect of oxygen deprivation on the concentration of these 3MH precursors during skin-contact maceration in two grape cultivars.
Methods and Results Müller-Thurgau (n = 19) and Sauvignon Blanc (32) grapes from Trentino (Italy) were hand harvested and processed under the following conditions: reductive (air protected; 80 mg/kg sulfur dioxide, 80 mg/kg L-ascorbic acid, and 200 mg/kg dimethyl dicarbonate) and oxidative (no addition of adjuvants and air contact). After maceration, GSH-3MH and Cys-3MH were analysed by liquid chromatography-mass spectrometry and isotopic dilution.
Conclusions Both GSH-3MH and Cys-3MH were identified for the first time in Müller-Thurgau juices. Oxidative maceration increased the GSH-3MH concentration in 16 out of 19 Müller-Thurgau and in 23 out of 32 Sauvignon Blanc juices, while Cys-3MH was higher in 13 and 20 juices, respectively, of the two cultivars. Parametrical and non-parametrical statistical tests confirmed that oxidative maceration of Müller-Thurgau increased GSH-3MH concentration significantly (P < 0.01).
Significance of the Study This work highlights the complexity of the mechanisms involved in the potential de novo formation of thiol precursors.
