Impact of Environmental Conditions on the Secondary Metabolite Evolution in Vitis vinifera. L. cv. Pinot Noir Grapes Under Cool Climate Conditions in South Africa
Erna H. Blanquaert
Luca A. Orselli
J.M. Ricardo-Da-Silva
Phenolic composition in red grape varieties is a key determinant of the final quality. The development of these compounds is dependent on the prevailing environmental conditions (light, temperature and water). Pinot Noir is a light skinned variety, and little is known about the development and identity of these compounds in the Hemel-and-Aarde and Elgin wine districts in South Africa. This study investigated the impact of light and temperature on the evolution of flavonols, anthocyanins and proanthocyanidins in the 2022-2023 growing season. Flavonol accumulation patterns differed between the two sites due to the variation in the photosynthetic active radiation withing the fruiting zone. The pattern of accumulation for each of the five mono-glucosides (i) Malvidin-3-O-glucoside (M-3-O-gl), (ii) Peonidin-3-O-glucoside (Pn-3-O-gl), (iii) Delphinidin-3-O- glucoside (D-3-O-gl), (iv) Petunidin-3-O-glucoside (Pt-3-O-gl) and (v) Cyanidin-3-O-glucoside (Cy-3-O- gl) varied throughout the season. Proanthocyanidin accumulation rate and concentration was influenced by the prevailing light and temperatures in the canopy. The mean degree of polymerization (mDP) in grape skins increased from 72 to 86 DAA, followed by a decrease to 106 DAA. The mDP in grape seeds and the average molecular mass (av MM) differed among the sites. The grape skin galloylation (%G) was lower than the seed galloylation (%G), of the proanthocyanidins, which was favoured by shading. Given the importance of Pinot Noir to produce sparkling wine and still table wine and the sensitive nature of the cultivar. This study provides valuable information on the secondary metabolite identity under cool climate conditions of Pinot Noir in South Africa.
Erna H. Blanquaert is a lecturer at the South African Grape and Wine Research Institute (SAGWRI), Department of Viticulture and Oenology, Stellenbosch University.
Luca A. Orselli is a researcher at the South African Grape and Wine Research Institute (SAGWRI), Department of Viticulture and Oenology, Stellenbosch University.
Jorge M. Ricardo-Da-Silva is Professor of Enology at LEAF—Linking Landscape, Environment, Agriculture and Food Centre and member of the Associate Laboratory TERRA, Instituto, Instituto Superior de Agronomia, Universidade de Lisboa.