Evaluation of glutathione content in white grape varieties

The aim of this work was to evaluate the content of glutathione in the grape, must and wine of nine white varieties authorized in the Qualified Designation of Origin Rioja (Spain): 'Chardonnay', 'Garnacha Blanca', 'Malvasia', 'Maturana Blanca', 'Tempranillo Blanco', 'Turruntes', 'Sauvignon Blanc', 'Verdejo' and 'Viura'. The results obtained showed important varietal differences in the concentration of GSH. 'Sauvignon' and 'Tempranillo Blanco' presented high levels of this compound in grape, must and wine. 'Verdejo' and 'Turruntes' registered high values in grape, which decreased notably in must and wine. In general, the GSH content decreased in musts due to oxidative processes. In 'Chardonnay', 'Garnacha Blanca', 'Maturana Blanca' and 'Viura' an increase was observed in wines, which could be caused by the inoculated yeast. The 'Malvasia' and 'Maturana Blanca' varieties registered the lowest level of this compound. The ratio of hydroxycinnamic acids to glutathione, indicator of the susceptibility of oxidation of musts, showed significant varietal differences, was lower in 'Sauvignon Blanc' and higher in 'Garnacha Blanca'.