Efeito da adição de glutadiona em vinhos e espumantes

Abstract

Sparkling wine, white wines as well, are very susceptible to oxidation in the processing stages and during storage and aging. Glutathione (GSH), present naturally in grapes and derivatives, is an antioxidant which positively contributes to the preservation of aromas, prevention of browning and other defects resulting from prolonged storage of white wines. The GSH molecule is very reactive due to its sulfhydryl group. In this sense, an alternative to preserve it and maintain its antioxidant properties for a longer period during the storage of sparkling wine would be the microencapsulation of GSH into a polymeric system. Microencapsulation of GSH could also prevent a negative aspect of the use of GSH in wine, which is inducing the formation of H2S (off-flavor), once the GSH is released slowly avoid oxygen reduced conditions in wine. In this context, this study aimed to evaluate the effect of adding free GSH in sparkling wine and prepare microcapsules containing glutathione to addition to the wine and/or sparkling wine. The free GSH (10, 20 and 30 mg L-1) was added at different stages (must, base wine and sparkling wine) of sparkling wine elaboration by the traditional method. The effects of the addition of GSH on aromatics compounds, phenolic compounds related to browning of white wines and on the free SO2 concentrations were evaluated. The analysis of phenolic compounds and the total and reduced glutathione were performed by high-performance liquid chromatography and UV spectrophotometry and; the analyzes of the aromatic compounds were made by gas chromatography. The microparticles containing GSH as active compound were prepared by spray-dryer with chitosan or β-cyclodextrin as polymers and their characterization was performed by scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), spectroscopy in the infrared with Fourier transform (FT-IR), X-ray diffraction (XRD). Furthermore, tests were performed to verify the recovery of GSH, the encapsulation efficiency and release kinetics of GSH in a model wine. The addition of GSH to the must influenced more in the sparkling wine composition than the addition to the base wine. However, the addition of GSH to the base wine appears to maintain higher levels of SO2 in its free form. The addition of 10 mg L-1 of GSH in the mus is sufficient for lower concentrations of caffeic acid, coumaric acid and ferulic in sparkling wine. The addition of 20 mg L-1 of GSH in the sparkling wine toghether with the expedition liqour resulted in lower color index, larger amounts of SO2 in free form, lower acetaldehyde concentration and same amount of phenolic compounds up to 12 months storage in bottle. The amount of GSH added to the ready sparkling wine declined in one month storage and stabilized within the first six months, but the amount of total glutathione remained higher in sparkling wine with addition of 30 mg L-1 until 12 months of storage. Although only GSH have antioxidant property, the total amount of glutathione had a higher correlation with the results obtained and therefore, the overall glutathione levels are a better indicator of wine antioxidant condition than GSH itself. It was possible to encapsulate glutathione using both, β-CD or chitosan. The characterization of microcapsules proved the micro surfacing of the active compound and an interaction between GSH and the polymers as well as improvement of the thermal stability of the molecule. The β-CD was more efficient for encapsulating GSH, allowing a gradual release of the molecule into model wine solution and added protection of the molecule, giving improved thermal stability for GSH.