Sabrina VOCE, Franco BATTISTUTTA, Lara TAT, Paolo SIVILOTTI, Piergiorgio COMUZZO
University of Udine, Department of Agricultural, Food, Environmental and Animal Sciences, Italy
Email contact: voce.sabrina[@]spes.uniud.it
AIM: This study aims at evaluating the effects of different refermentation methods (Martinotti/Charmat vs. Classic) on the chemical composition, aroma profile and sensory characteristics of Ribolla Gialla sparkling wines; furthermore, certain winemaking practices (skin contact and use of pectolytic enzymes) were investigated considering the extraction of varietal aromas and aroma precursors.
METHODS: Sparkling wines were produced at pilot-plant scale. Concerning refermentation methods, traditional Martinotti (MB – 30 days length), extended Martinotti (ML) with 4 months of aging on lees and Classic method (CL) with 11 months of aging on lees were compared; in a second trial, skin contact (MM), enzyme addition on must also subjected to maceration (ME), and enzyme addition on base wine (VE) were evaluated. All experimental trials were performed in triplicate. Basic chemical composition, varietal (terpenes and C13-norisoprenoids in free and bound form) and non-varietal aroma compounds were evaluated by LLE-GCMS analysis; finally, sensory analysis was also performed, by descriptive testing.
RESULTS: Basic chemical composition was influenced by refermentation method, with higher acidity and lower pH in MB and the occurrence of malolactic fermentation in ML and CL. The aroma profile was also affected by winemaking practices applied. In sparkling wines produced by MB, a higher concentration of trans-geraniol was observed; this is the only terpenol found Ribolla Gialla grapes , even if below its odor threshold ; however, the aroma profile of MB sparkling wines was mainly characterized by esters that generally confer fresh, fruity and floral notes to the wines (e.g., hexyl acetate) ; on the other hand, esters formed during ageing (e.g., ethyl lactate) together with fatty acids and higher alcohols were found in higher concentration in CL sparkling wines, making their aroma profile more complex; finally, wines obtained by ML showed the poorest volatile profile. These results were also confirmed by sensory analysis.
Skin contact and especially enzyme addition on base wine allowed to obtain a higher extraction and release of some varietal aroma compounds (e.g., geraniol, linalool and α-terpineol), even if below their odor thresholds. The same trend was observed for C13-norisoprenoids, except for β-damascenone. Concerning non-varietal aroma compounds, sparkling wines obtained by MM and ME showed the highest concentration of some esters (e.g. isoamyl acetate), probably related to a greater extraction of their precursors (amino acids) from grapes [4, 5].
CONCLUSIONS: The overall chemical composition and sensory profile of Ribolla Gialla sparkling wines are significantly affected by the enological practices used. These results may address winemakers to produce Ribolla Gialla sparkling wines, tailored on market needs and consumer’s preference.
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