Evaluation of glutathione content in four white varieties in the d.o. Ca. Rioja (Spain)

Abstract

AIM: Glutathione is a tripeptide that is mainly found in reduced form in grapes. It generates during the maturation of the grape, increasing significantly after veraison [1]. It plays a relevant role in the prevention of oxidative processes due to its high antioxidant activity. Its content in the grape is influenced by many factors (variety, vintage, cultural practices, nitrogen nutrition …) [2]. In musts and wines, it undergoes modifications due to oxygen exposure, tyrosinase activity, maceration time, pressing, yeast strain…[3]. The aim of this work was to evaluate the content of glutathione in the grape of four white varieties: Tempranillo Blanco, Maturana Blanca, Garnacha Blanca and Viura.

METHODS: The study was carried out during three seasons (2017, 2018 and 2019) in a vineyard located in the D.O.Ca. Rioja (Spain). On the other hand, the influence of different vineyard locations on the content of this compound in the indicated varieties was also analyzed. Glutathione determination was carried out by HPLC by automatic derivatization in precolumn with OPA. The previous extraction in the grape was carried out with HCl/EDTA [4].

RESULTS: The results obtained showed important varietal differences in the glutathione content of the grape in the white varieties studied. The highest concentration was obtained in the Tempranillo Blanco variety, although without significant differences in comparison to Viura, while the lowest levels corresponded to Maturana Blanca and Garnacha Blanca. Also, the characteristics of the vintage also influenced its concentration, although the varietal differences were maintained. The location of the vineyard showed a variable effect depending on the vinifera, and the characteristics of the vintage in the case of Tempranillo Blanco.

CONCLUSIONS

These results confirm that the variety is one of the most influential factors in the glutathione content in grapes. Tempranillo Blanco has high levels of this compound, which can help preserve the quality of your wines.