From amino acids to aroma: evaluation of grape aroma potential

Abstract

Wine aroma is a major determinant of quality and typicality and originates from the interaction between grape-derived precursors and fermentation-related metabolites. While the aromatic potential of grapes and must has traditionally been evaluated through well-known classes of aroma precursors, growing evidence highlights the central role of free amino acids in shaping fermentative aroma. Amino acids act as direct precursors of key volatile compounds, including higher alcohols and esters. The amino acid profile of must is highly variable and depends on cultivar, vineyard practices, climate conditions, and fruit maturity, contributing significantly to differences in volatile composition and aroma expression. However, correlations between amino acid composition and aroma formation requires further investigations with the purpose to integrate amino acids into models for the assessment of the grape aromatic potential. Sixteen musts from different grape varieties (Riesling, Pinot noir, Nero d’Avola) were characterised in terms of general chemical parameters, amino acid profile and aroma precursors. These musts were fermented under controlled conditions without performing any correction. Moreover, the content of nitrogen was adjusted for the two nitrogen-poorer musts by adding different nitrogen sources, including diammonium phosphate, pool of amino acids, 9 essential amino acids and yeast extract. Once the fermentations were completed, the wines were analysed for general chemical parameters, amino acid profile, aroma precursors and volatile compounds. Fermentative vigour and power were lower for musts poorer in nitrogen with an additive decrease in case of more acidic pH. The addition of the selected nitrogen sources led to increased fermentative vigour and power being more relevant when the yeast extract was used. In any case, all the fermentations were completed. Negligible differences were found for lactic acid, while larger variation was observed for acetic acid. The volatile composition was affected by the nitrogen source in particular for certain higher alcohols and esters, the former being higher with inorganic nitrogen. Organic nitrogen led to major content of esters, in particular of acetate esters when yeast extract was supplemented. This study advanced the evaluation of grape aromatic potential and can support the development of predictive tools applicable to vineyard management and valorisation of varietal and terroir-specific aromatic expression.

Funding

The study was supported by Supply Chain and District Contracts (5th call) project “White Wine Identity: new horizons for an integrated and sustainable development of the Italian white wine supply chain” funded by the Ministry of Agriculture, Food Sovereignty and Forests. Grant number: PRI-1058; MASAF public call n.182458 22-04-2022, D.D. MASAF 15.11.2023 n. 633056-position n.62; D.M. n. 0264374 12.06.2024, D.M. n. 399082 28.07.2023, n. 633056 15.11.2023 and n. 559310 23.10.2024.