Influence of Glutathione and Ascorbic Acid Treatments during Vinification of Feteasca Regala Variety and Their Antioxidant Effect on Volatile Profile

Abstract

Volatile profiles were determined for white wines of Feteasca regala variety produced from musts in which the antioxidants glutathione and ascorbic acid were added in different proportions before inception of alcoholic fermentation. Treatments with these antioxidants affect some volatile compound evolution and positively influence the wine volatile profile. After one year of storage in bottles with and without carbon dioxide protection the volatile profiles of the wines were assessed by using a Fast GC Alpha MOS Heracles e-Nose by applying a DFA multivariate statistical method and AroChemBase database for compound identification. The analyses showed that some higher alcohols, such as 2-phenylethanol and 2-methyl-1-butanol were in lower concentrations in wines treated with reduced glutathione, while the main ethyl fatty acid esters, such as ethyl butanoate, ethyl hexanoate, ethyl octanoate, and ethyl decanoate were better preserved when higher concentrations of any of the antioxidants were added in must. On the other hand, it was observed that some other volatile compounds were not affected by these applied treatments.

Evaluation by Flash GC Electronic Nose of the Effect of Combinations of Yeasts and Nutrients on the Aromatic Profiles of Feteasca Regala Wines after Two Years of Storage

“…The less-expressed thiolic character of the Thiol-TXL sample-unexpected because the use of the TXL yeast and the addition of the Thiol nutrient should have led to the contrary result-can be explained by a possible degradation or combination during storage of the thiolic compounds. There is a very fine redox balance in the white wines, especially when they contain glutathione (in our case from the OptiThiol nutrient), which enhances aroma in a reductive medium, but can act as an oxidant in higher concentrations [29]. Finally, the relative similarity and closeness in the sensory PCA space of samples Ester-STR and Thiol-STR on one hand and samples Ester-TXL and Thiol-TXL on the other hand point out that the wine aroma is more strongly modulated by the yeast, and to a lesser extent, by the added nutrients.…”

“…Additional information on the Alpha MOS Heracles analyser and methods used can be found in previous papers [29,30,[37][38][39][40][41]. The software used by the Heracles electronic nose for data recording and processing was AlphaSoft v12.42, and the library AroChem-Base version 2010 (Alpha MOS, Toulouse, France) was used for the identification of chemical compounds based on retention Kovats indices.…”

“…The e-nose experimental parameters, examples of chromatograms obtained on both columns with this e-nose, the method for selecting the sensors (represented by chromatographic peaks), and the method for calibration and calculation of Kovats indices can be found in a previous paper [29].…”

“…Thiols, however, result mainly from the hydrolysis of the cysteinylated and coumaroylated thiolic compounds of grapes [49]. They are very fragile and easily oxidized; therefore, they are found in lower quantities in aged wines, especially when the wines are from varieties with low thiolic aroma precursors, such as Feteasca regala, in which they are not usually detected [29,50].…”

“…The electronic nose technology is very good at sensing minute differences among the experimental variants, and many studies take advantage of its discrimination power [26][27][28][29], its rapidity [30] and also attempt to eliminate human evaluators [31]. However, for our study, the compounds that the electronic nose was able to separate and identify were not sufficient to thoroughly describe the aroma profile of the wines; therefore, combining both approaches-electronic nose and sensory evaluation-led to a better evaluation and discrimination of the samples.…”