Quality of Merlot wines produced from terraced vineyards and vineyards on alluvial plains in Vipava valley, Slovenia (pdo)

Abstract

AIM: Different factors affect the style and quality of wine and one of the most important are environmental factors of vineyard location. The aim of this study was to compare the quality of Merlot wines produced from grapes growing on skeletal and dry soils of terraced vineyards and deep loamy soils of alluvial plains of Vipava Valley, a warm climate winegrowing district in Slovenia.

METHODS: Five vineyards on terraces and five on alluvium plains were chosen. Viticulture parameters such as number of buds, number of clusters and leaf area on each vine were unified in 2019 and 2020 as described in Sivilotti et al. (2020). Stem water potential (SWP) was measured during the season (Deloire and Heyns, 2011). 5 kg of grapes were sampled in triplicates at the time of grape maturity. Basic physicochemical parameters of grapes were determined before microvinification. Microvinifications were analysed after alcoholic and malolactic fermentation. Concentration of total phenols (TP), total anthocyanins (TA), high (HMWP) and low molecular weight (LMWP) proanthocyanidins (PAS) were determined spectrophotometrically as described in Rigo et al. (2000). Moreover, structural characteristics of PAs in wines, i.e. mean degree of polymerisation (mDP), percentage of galloylaton (%G) and percentage of prodelphinidins (%P) were determined by UHPLC-DAD-MS/MS as described in Lisjak et al. (2019) and in Sivilotti et al. (2020). Esters were analysed by GC-MS (Bavčar and Baša Česnik, 2011) and higher alcohols by GC-FID (Bavčar et al., 2011).

RESULTS: SWP was more negative on terraces. According to basic physico chemical parameters and darker seed colour, grapes from terraces showed advanced ripening in comparison to grapes grown in alluvial plains. Wines from terraces had higher concentrations of TA, TP, HMWP, ash and total dry extract in comparison to wines from alluvial plains and PAs reported higher %G. Furthermore, aromatic profiles of wines were also different. In general, higher concentrations of higher alcohols and lower concentrations of esters were detected in wines from terraces.

CONCLUSIONS:

 The Merlot wines from grapes sampled in terraced vineyards differed in chemical composition from those from alluvial plains. In general, wines from terraces had higher polyphenol content, some quality parameters such as ash and total dry extract, structural differences of grape tannins and different profile of some aroma compounds