Caputo, Annina (2025) Elemental profile and enological characteristics of Aglianico cv grapes from a quality wine Terroir (Taurasi DOCG) in southern Italy: analysis of the relationship with soil composition and chemical properties among vineyards, and their spatial variability at vineyard scale. [Tesi di dottorato]

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Abstract

This study explores the intricate interplay of soil chemical properties, grape elemental profiles and enological characteristics in the context of the quality wine terroir of the Taurasi DOCG (Campania Region, Southern Italy), focusing on the native Aglianico cv. This research aims to contribute to the knowledge of the role played by the soil environment on the grape element composition, maturation indices and phenolic compounds applying a multidisciplinary approach at two scales, the terroir and vineyard scales, to address the dual challenges of wine quality improvement, starting from the knowledge of the grape composition, and of vineyard management adaptation to pedoenvironment peculiarities. In detail, the chapter 2 focused on the relationship between the soil element composition and the grape element profile to investigate attributes of grape mineral uptake in the soil-plant system and relate them to the enological characteristics and the phenolic content of the wine. In five vineyards of the Taurasi terroir, selected in homogeneous environmental conditions, the element profiles of grape tissues and wine-like juice (WLJ) laboratory extracts, simulating the potential wine, as well as the soil bioavailable element content, were determined by measuring B, Ca, Cu, Fe, K, Li, Mg, Mn, Na, P, Si, Sr, and Zn concentrations, using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). The research applied a combination of statistical approaches, including Kruskal-Wallis ANOVA, to assess differences among vineyards, and Principal Component Analysis (PCA) to identify key soil parameters influencing grape quality. Inferences on soil-grapes mineral uptake processes were made by calculating elements bioconcentration factors (BFs) in the grape tissues by the soil bioavailable element content. Significant correlations were found between BFs and grape enological characteristics (i.e., pH, total soluble solids, titratable acidity, berry weight), WLJ phenolic content (anthocyanins, tannins and total phenolic compounds), and soil properties (i.e., cation exchange capacity, exchangeable bases, pH, organic carbon, total carbonates, electrical conductivity, soil texture), highlighting the relationship between soil-plant interaction and winegrapes quality parameters. The preferential transfer of elements from pulp and skin to WLJ was evaluated by transfer coefficients (TCs). Similar order (K > P > Ca > Mg > Si > Na > B > Fe > Cu > Zn > Mn ≥ Sr > Li) of element content between grape tissues and WLJ was assessed. Highly significant revealed the Spearman correlation coefficients between the WLJ and the seeds content of Mg and Sr, between the WLJ and the pulp content of B, Ca, K, Mg, Mn, Na, Si and Sr, and between the WLJ and the skin content of K, Mg, Na, Si and Sr. Therefore, it is possible to suppose Mg and Sr transfer from all the grape tissues, K, Na and Si preferential transfer from both pulp and skin, while only from pulp for B, Ca, Mn. Iron, P and Li content of the grape tissues did not show any correlation with those in the WLJ. The results of the Kruskal-Wallis ANOVA and PCA assess high homogeneity of grape and soil characteristics among the vineyards, confirming the uniqueness and peculiarity of the Taurasi terroir. Nevertheless, along the PC1 (accounting for 29% of the total variability), a separation on the positive scores of the two vineyards belonging to Mirabella Eclano (one of the two villages of grape origin) with respect to those from Montemarano on the negative scores. Among the variables accounting for the difference, the soil EC, pH, silt, Kex and Naex were found related to grape pH, bound and total anthocyanins, tannins, and to the BFs of Si, P, Cu, S, Zn, Mn, Li; on the contrary, the soil sand and the organic carbon were associated with titratable acidity, berry weight and Caex and to the BFs of K, Na, Mg, Sr. Building on the findings of Chapter 2, Chapter 3 delves deeper into the terroir-driven variability of Aglianico cv grapes with an intra-vineyard focus by integrating vineyard zoning techniques and soil spatial variability analyses. Conducted within three vineyards (VD, VB and VS) located in the Montemarano village, the research employed precision viticulture tools of soil proximal sensors, including electromagnetic induction (EMI), gamma-ray spectrometry (γ-ray), and portable X-ray fluorescence (XRF) sensors to delineate homogeneous zones (HZs) within vineyards. The continuous maps obtained from kriging, together with the aspect and slope maps by digital earth model (DEM), were used as input for a clustering analysis. Four homogeneous zones (HZs) were identified within the vineyards. Soil and grape samples were analysed across the intra-vineyards HZs to examine the relationship between soil heterogeneity in the HZs and grape phenolic composition, anthocyanin content, and enological traits, utilizing wine-like solutions (WLS) as a proxy for wine composition, to predict the potential extractability of phenolic compounds. A factorial ANOVA was applied to evaluate the effects of vineyard zoning and vintage on grape maturation indices, phenolic composition, and anthocyanin profiles. Results showed that vineyard-specific effects accounted for over 55% of the variability in berry weight and volume, along with most of the identified native anthocyanins, while climate significantly influenced acidity, tannins, and total phenols. The 2021 vintage, characterized by hot and dry conditions, resulted in smaller berries with higher sugar content and phenolic concentration, while the 2022 vintage, with its cooler and wetter conditions, yielded grapes with higher acidity and a balanced phenolic composition. The PCA results, explaining more of 70% of the total variance, identified four principal components (F1, F2, F3 and F4) shaping grape composition. F1 was primarily associated with anthocyanin-related traits and berry structure, with petunidin-3-glucoside and malvidin-3-glucoside emerging as key contributors. F2 was dominated by grape structural traits such as the skin/berry ratio and pulp/berry ratio, along with soil-related attributes like CEC and calcium content. F3 focused on acidity and seed phenolics, while F4 highlighted seed-specific tannin characteristics. The PCA scores plot revealed distinct clustering by vineyard and vintage, with the 2021 vintage exhibiting greater dispersion along F1 and F2, indicative of environmental variability, whereas 2022 formed a more compact cluster, closely aligned with phenolic maturity indicators such as °Brix and anthocyanins. By linking soil composition, elemental profiles, and enological attributes through zoning methodologies and advanced multivariate analysis, this study provides a comprehensive framework for sustainable viticulture. The results highlight the importance of terroir-driven vineyard management in producing high-quality wines reflective of their regional typicality and identity, while also addressing the challenges posed by climate variability.

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