Feasibility of pre-fermentative oenological tannins addition to enhance volatile composition and aroma perception in white wines

Abstract

Oenological tannins (OETs) are an alternative to sulphur dioxide due to their antioxidant and antioxidase properties in the early phase of winemaking [1,2]. The addition of OETs can affect both the concentration and perception of volatile organic compounds (VOCs) contributing to wine aroma. This study aimed to evaluate the impact of pre-fermentative addition of OET formulations from different origin on sensory descriptors and VOCs of wines from the Vitis vinifera L. white grape varieties ‘Favorita’ and ‘Erbaluce’.

Six OET formulations were selected and characterised: exotic woods Acacia (AC) and Quebracho (QB), grape seeds (SD), grape skins (SK), wood hydrolysable tannins based on gallic acid (GL) and ellagic acid (EL). OETs were added to grape must before alcoholic fermentation at equal polyphenol concentrations (calculated on absorbance at 280 nm, TPI) and compared to a control without addition (CT). Basic compositional parameters, total polyphenols and antioxidant capacity (spectrophotometric indexes), CIELab coordinates were investigated pre- and post-fermentation [3,4]. VOCs were quantified using HS-SPME GC-MS on final wines [5]. Sensory analysis was performed by a trained panel for mouthfeel and aroma attributes by descriptive analysis (DA) and check-all-that-apply (CATA), respectively [4].

The fermentation kinetics were not affected by using OETs. TPI increased uniformly across treatments after OETs addition, but antioxidant capacity and colour varied depending on the OET formulation (AC, SD, and SK musts showing higher values). In Favorita treated wines, colour was not different from CT (ΔE<3) and the final TPI was slightly influenced by OETs. Instead, Erbaluce AC, EL, and SD wines showed ΔE>3 (compared to CT) and higher TPI value. Sensorially, bitterness was not affected, but astringency intensity increased in EL-treated wines in both varieties, and in SD-treated wines for Erbaluce, but not differently from CT. Aroma intensity significantly differed (p<0.05) in Favorita, with QB and EL wines showing the highest value, and AC the higher overall quality (p<0.05). For Erbaluce, SK and QB wines resulted in higher overall quality (p<0.01). In Favorita, differences among samples were found in pineapple (p<0.05) and banana (p<0.1) descriptors. AC-Favorita and SK-Erbaluce shared high frequency of pineapple, and QB-Favorita of green apple and banana descriptors, which rely on individual ethyl esters over perception thresholds. Indeed, for both varieties total VOCs did not significantly change by OETs addition, but specific classes did. In Favorita, the SD tasted wine showed higher concentrations of terpenes and volatile acids compared to CT, while OET-added Erbaluce wine presented lower benzenoid content.

The addition of OETs can influence the aroma profile of white wines in different extent depending on the formulations and the varietal composition without compromising negatively the mouthfeel properties.