Effect of Composting Treatment of Grape Branches on Wine Quality

In order to study the effect of applying different proportions of compost made from grape branches in the vineyard on the quality of wine, 8-year-old ‘Pinot Noir’ grapevine was selected for this study, and compost made from 100% crushed grape branches (GB), compost made from 70% crushed grape branches + 30% sheep manure (GM1), compost made from 50% crushed grape branches + 50% sheep manure (GM2), compost made from 30% crushed grape branches + 70% sheep manure (GM3), and 100% sheep manure (SM) were applied to the vineyard, and the no compost addition treatment (CK) was used as a control. One year after fertilization, grape berries were taken to brew wine, and the basic physicochemical indexes of grapes and wine, the phenolic substances, color, and aroma substances and sensory evaluation of wine were determined. The results showed that the composting treatment significantly increased the contents of alcohol, total phenols, total anthocyanins, total flavan-3-ols, and total flavonoids in Pinot Noir wine, with the GM3 treatment showing the greatest increase in the levels of alcohol and titratable acids, by 16.5% and 24.03%, respectively. In terms of color, the composting treatments increased the color saturation of ‘Pinot Noir’ wine. Orthogonal partial least solid-phase analysis (OPLS-DA) of aroma substances showed that the major differential aroma substances in ‘Pinot Noir’ wine among different composting treatments were isoamyl alcohol, followed by ethyl acetate, 1-propanol, and phenylethanol, and that composting treatments with the addition of grape branches increased the levels of ethyl acetate, isoamyl acetate, ethyl caproate, and ethyl caproate in ‘Pinot Noir’ wine. In terms of sensory quality, the intensity of astringency, bitterness, and sweetness of ‘Pinot Noir’ wine was enhanced by the composting treatments, and the wine was improved in terms of taste and balance. This study provides a theoretical basis for the comprehensive utilization of grape branch waste and the improvement of wine quality.