Volatile Compound Release from Oak Chips in Model Wine Media: Combined Influence of Toasting Degree, Size, Time of Contact, and Ethanol Content

: The effects of size, toasting degree, and time of contact on the release of volatile compounds from Quercus alba (L.) chips during a simulated fermentation and post-fermentative process were studied. The results obtained indicated that the large-size chips favored the release of furfural and furfuryl alcohol, while the small ones increased the concentration of cyclotene and maltol. The interaction between chip size and time of contact showed that the small-size chips are more sensitive to the increase of ethanol concentration for the extraction rate of some compounds (furfural, vanillin, maltol, cyclotene, whiskey lactones, and eugenol) compared to the large-size ones, increasing their concentrations at the end of maceration. The toasting degree of oak chips had a different influence on the volatile compounds studied. Cyclotene and guaiacol concentrations increased with the toasting intensity, whereas the extracted concentration of all compounds increased from light to medium-toasted chips, except for eugenol, and then decreased by further increasing the toasting level for 5-methylfurfural, whiskey lactones, eugenol, and only using high-level toasted chips for furfuryl alcohol, maltol, and vanillin. A possible protection effect of the chip size toward the possible degradation or volatilization losses of furfural for high toasting degrees was observed.