Effects of biodynamic preparations on grape skin structure and composition

Biodynamic viticulture, with its holistic philosophy, is gaining traction among professionals in the French wine industry. This approach incorporates the use of compost, herbal infusions, and organic and mineral preparations. Many biodynamic winegrowers highlight the impact of these preparations on the development of grape skins during ripening. While some believe that these preparations strengthen grape skins, others contend that they increase skin degradation. Nonetheless, there is a broad consensus that these preparations contribute to enriching grape skins with phenolic compounds and aromas. However, few scientific studies have specifically examined the effects of biodynamic preparations on grape skin evolution during berry development and maturation. The aim of this study is therefore to provide insights into the potential effects of biodynamic preparations on grape skin structure and composition, as well as to investigate the underlying mechanisms. The research was conducted over three consecutive vintages (2022, 2023, 2024) on approximately four hectares of Cabernet Sauvignon grafted onto Riparia Gloire de Montpellier rootstock, cultivated organically on gravelly-sandy soils at Château Lafite Rothschild (Pauillac, France). A full-field alternating strip design allowed for the establishment of eight blocks, four of which received biodynamic preparations (500, 501, CPP) (BD treatment), while the remaining four served as an experimental control treated organically (AB treatment). We analysed the structural and biochemical changes in grape skins – specifically in pectic polysaccharides, tannins, flavanols, flavonols, and stilbenes – across four key phenological stages: fruit set, cluster closure, véraison , and maturity. In addition, skin texture was assessed via the skin permeability index and penetrometry. Certain parameters of the skin were significantly modified by the application of biodynamic preparations. BD-treated skins displayed wider cells and thicker cell walls. Additionally, the reduced activity of pectin-methylesterase (PME) in these skins appeared to limit the depolymerization of polysaccharides and decrease the dissociation of the pectin network by other enzymes. Observations regarding skin polyphenols, although not statistically significant , were noteworthy. Concentrations of flavanols, flavonols, and piceids—molecules involved in the plant’s defense metabolism—were more elevated for BD berries. The impact of these morphological and biochemical modifications on the berries' susceptibility to Botrytis cinerea was analysed for the final vintage of the study in 2024, revealing a significant decrease in susceptibility for BD-treated berries.