Astringency subqualities and the sensory-chemical drivers of wine typicality: A study on Nebbiolo wines

Abstract

Typicality is a multidimensional concept resulting from the interplay of intrinsic and extrinsic characteristics. Among intrinsic factors, grape variety and its associated varietal traits is central in shaping aroma, flavour, basic taste, and mouthfeel, although winemaking practices and ageing influence the final wine profile. ‘Nebbiolo’ is a grape variety native to north-western Italy and is the basis of several DOCG (Denominazione di Origine Controllata e Garantita) wines, the highest level in the Italian designation of origin system. The Piedmont region represents the core of ‘Nebbiolo’ production, with renowned DOCG such as Barbaresco, Barolo, Gattinara, Ghemme, and Roero. In this study, 65 Nebbiolo wines (aged 3-8 years at the time of analysis) from these DOCGs were collected and then chemically and sensorially analysed with a specific focus on tannin traits and mouthfeel. Tannin content was assessed using methylcellulose precipitation assay, flavanols reactive to vanillin, bovine serum albumin assay, together with total polyphenols and flavonoids by spectrophotometric methods. Tannin composition was determined by phloroglucinolysis. Two sensory evaluations were conducted: a trained panel performed a mixed descriptive analysis and Check-All-That-Apply (CATA) methodology to investigate astringency subqualities, while an expert panel evaluated oxidation, balance, and in-mouth typicality. Wine differences were explored by multivariate analysis and ANOVA. Relationships between expert-rated typicality and both sensory and chemical parameters were investigated using Pearson correlation and partial least squares regression (PLSR). The analysed Nebbiolo wines were characterised by Powdery particulate, Fine grain surface smoothness, and a Dry mouthfeel. Powdery and Dry were positively correlated with tannin content. The Fine grain descriptor was positively correlated with in-mouth typicality, that was also positively linked to a higher degree of tannin galloylation and epicatechin subunits (%) and negatively with the chain length (mDP). PLSR model revealed limited predictive ability of tannin instrumental data alone for in-mouth typicality. Improved power was achieved using sensory descriptors. These results suggest that tannin instrumental analysis can partially explain in-mouth typicality and pave the way towards additional parameters evaluation or an increased sample number to improve the performance of these predictive models.