Evolution of phenolics and glutathione in Verdicchio wine obtained with maceration under reductive conditions

- Reductive condition and skin contact increase reduced glutathione and phenols level.
- The highest level of reduced glutathione was less than 2 mg L−1 in must.
- A 6-months ageing period lead to the complete degradation of reduced glutathione.
- The precursor of ethyl caffeate is caffeic acid, after hydrolysis of caftaric acid.
- The formation of ethyl caffeate is limited by steric hindrance of caftaric acid.

The aim of this study was to evaluate the influence of different skin contact percentage (0, 150 and 600 g L−1 of pomace), on the phenolic content and on the reduced glutathione levels in white Verdicchio musts and in the derived wines by using reductive conditions in an industrial winery. The results were compared with those from a control must obtained without maceration. The samples were taken after pressing, during alcoholic fermentation and after six months of storage. The skin contact in low-oxygen atmosphere lead to an increase of the phenolic content and glutathione in must and white wine. At the end of fermentation, the macerated samples with pomace at 600 g L−1 showed higher reduced glutathione and phenolic content, with respect to the other samples. Glutathione and tyrosol were positively correlated with yeast activity but then decreased during ageing. Ethyl caffeate increased in all samples during fermentation and wine ageing, thus confirming its origin as a condensation product between caffeic acid and ethanol after the hydrolysis of caftaric acid.