Investigating the relationship between grape cell wall polysaccharide composition and the extractability of phenolic compounds into Shiraz wines. Part I: Vintage and ripeness effects

•Phenolic and polysaccharide compositions of Shiraz grapes and wine were investigated.•Vintage and ripening both influenced polysaccharide and phenolic composition in the grapes.•Grape berry intactness was influenced by the cell wall composition. Phenolic compounds play an important role in colour stability and sensory properties of red wine. This study evaluated berry skin cell wall composition and how this influences grape and wine phenolics at different ripeness levels (21°Brix, 23°Brix, and 25°Brix) over two consecutive vintages. The vintage effect was highly significant, especially in the pectin fraction of the grape cell walls and affected the concentrations of certain phenolics extracted. The climatic variance between the seasons might have influenced the differences observed in the grape cell wall compositions. Firstly, a higher grape and wine phenolic content, especially in polymeric phenols, was found in 2015 wines. Additionally, grape berry cell walls, especially at the earliest stages of ripening, were found to be more intact in 2015 than in 2016. Thus, a possible relationship was found between the degree of berry intactness, especially for pectin-rich components, and the corresponding phenolic extractability during the winemaking.