Comparison of the Suitability of Different Hydrolytic Strategies To Predict Aroma Potential of Different Grape Varieties

Abstract

Precursor extracts obtained from different grape varieties were submitted to harsh acid hydrolysis (pH 2.5, 100 degrees C, 1 h) and enzymatic hydrolysis (AR2000, pH 5, 40 degrees C, 16 h) and were also added to a synthetic must (200 g L(-1) glucose), which was fermented (yeast strain Stellevin NT 116), to compare the "natural hydrolysis" carried by yeast with alternative "fast" hydrolytic strategies. In all cases, released volatile compounds were extracted by SPE and determined by GC-MS. Leaving aside Muscat, differences between varieties were not relevant, although Grenache and Chardonnay presented some key peculiarities. In general, alcoholic fermentation showed the lowest potential to release volatile compounds from aromatic precursors, whereas enzymatic hydrolysis was the most efficient but also the most different. Practically, this implies that the predictive ability of this hydrolytic strategy is rather poor. In contrast, harsh acid hydrolysis can be considered to much more adequately measure the aroma potential of grapes for winemaking, which suggests that transformations taking place during fermentation include relevant chemical rearrangements in acid media that are better predicted by acid hydrolysis.

Glycosidically Bound Volatile Aroma Compounds in Grapes and Wine: A Review

“…Acid hydrolysis is less cost prohibitive and can be done more quickly compared to enzymatic hydrolysis. Acid and enzyme hydrolysis procedures were compared in a study (Loscos et al 2009), and while the enzyme hydrolysis occurred over 16 hr, the acid hydrolysis was completed in one hr. Seven different grape varieties, both red and white, were tested, and while the enzymatic hydrolysis appeared to release a higher concentration of terpenes (3 to 10x) for five of the seven cultivars, released norisoprenoid concentrations were greater by a factor of 10 for the acid hydrolysis procedure for all cultivars.…”

Exposure of grapes to smoke of vegetation with varying lignin composition and accretion of lignin derived putative smoke taint compounds in wine

“…Given that grapevine lignin contains syringyl derivatives archetypal of a woody angiosperm (Guillén & Ibargoitia,1996) and that grape juice was fermented on skins (thus facilitating hydrolytic release of lignin units into wine (Loscos, Hernandez-Orte, Cacho, & Ferreira, 2009)), the presence of syringyl derivatives, albeit at high levels, is plausible (see also Singh et al, in press). The observed significant increases in the concentrations of total syringols and substituted syringols in wines impacted by smoke of the angiosperm fuels (the three hardwoods and wild oat) may be attributable to exogenous uptake due to the presence of syringyl derivatives in fuels (Table 2) and more significantly in their smoke emissions (Table 3).…”

Influence of cluster zone leaf removal on Pinot noir grape chemical and volatile composition

“…Only a small portion of grape volatile compounds are present in their free forms, and the majority exist in non-volatile, glycosidically-bound forms or other precursor forms (Gunata, Bayonove, Baumes, & Cordonnier, 1985;Winterhalter, Sefton, & Williams, 1990). However, these non-volatile precursors can be converted to the volatile form through enzymatic or chemical hydrolysis during vinification and aging, thus contributing to wine aroma (Gunata, Bitteur, Brillouet, Bayonove, & Cordonnier, 1988;Loscos, Herná ndez-Orte, Cacho, & Ferreira, 2009;López, Ezpeleta, Sánchez, Cacho, & Ferreira, 2004).…”