Impact of Foliar Application of Winemaking By-Product Extracts in Tempranillo Grapes Grown Under Warm Climate: First Results

The Tempranillo grape variety is the most widely cultivated red grape cultivar in Spain. However, it has been observed that this variety may not always exhibit the optimal colour properties in warm climates such as Andalusia (southern Spain). Several strategies have been proposed to enhance productivity and resilience to stress or improve the quality of both grapes and wines. The foliar application of agricultural plant extracts has been identified as a highly effective method of promoting the synthesis of secondary metabolites in the grapevine. The objective of the current research was to analyse the incidence of foliar application of different extracts from winemaking by-products (grape stems: GS, grape pomaces: GP and wine lees: WL) on Tempranillo grapevine leaves, studying the impact on the quality of the resulting wines. The oenological and colour characteristics of the wines were assessed to evaluate the impact of these extracts on wines during the winemaking process. The detailed composition of the wines revealed that GS and WL extracts led to significant differences in wine colour properties. Wines derived from grapes treated with both extracts exhibited heightened colour intensity, accompanied by discernible alterations in CIELab coordinates, with lower L* and higher a* and C*ab values in comparison to CT. These results are encouraging, and the foliar application of GS extracts at veraison appears to be a feasible alternative to enhance the colour of wines from red grape cultivars with colour difficulties in warm climates.