Chitosan Hydrochloride Applied as a Grapevine Biostimulant Modulates Sauvignon Blanc Vines’ Growth, Grape, and Wine Composition

An increasing trend toward alternative methods in grapevine protection is evident, diverging from conventional chemical approaches. Biostimulants, such as chitosan hydrochloride, are compounds able to elicit the synthesis of plants’ metabolites, leading to an increase in their natural defence mechanism. Some of these metabolites could potentially impact wine sensory properties such as colour, mouthfeel, and aroma. This study investigates the effect of chitosan hydrochloride treatment on Sauvignon blanc vines, isolating impacts on plant, grape, and wine levels. Using a randomized block design with 74 potted plants grown in a glasshouse, the study found that foliar chitosan application did not affect plant growth or phenolic compound accumulation in the leaves. Conversely, it significantly decreased polyphenol oxidase (PPO) activity and increased antioxidant activity and polyphenolic content in grape berries. Treated berries exhibited doubled protein content, less thaumatin-like proteins, and more β-glucanases and chitinases than control grapes. Microvinifications revealed that wines from treated grapes had higher total polyphenols, polysaccharides, Abs 320 nm values, and total proteins than control wines. These preliminary results suggest that chitosan application affects key grape metabolites with potential implications for wine quality, warranting further investigation.