The Effect of Vineyard Cover Crop on Main Monomeric Phenols of Grape Berry and Wine in Vitis viniferal L. cv. Cabernet Sauvignon

Abstract

This study was conducted to determine the effect of cover crop inter-row in vineyard on main mono-phenol content of grape berry and wine. Three such cover crops, two perennial legumes (white clover and alfalfa) and a perennial gramineous grass (tall fescue) were sown in vineyard. The main phenolic compounds of mature grape berry and wines vinified under the same conditions were extracted with ethyl acetate and diethyl ether and analyzed by high-performance liquid chromatography (HPLC) by comparing to soil tillage. A total of ten phenolic compounds were identified and quantified in the different grape berry and wines, including nonflavonoids (hydroxybenzoic and hydroxycinnamic acids) and flavonoids (flavanols and flavonols). The concentration of flavonoid compounds (409.43 to 538.63 mg kg −1 and 56.16 to 81.30 mg L −1) was higher than nonflavonoids (76.91 to 98.85 mg kg −1 and 30.65 to 41.22 mg L −1) for Cabernet Sauvignon grape and wine under different treatments, respectively. In the flavonoid phenolics, Catechin was the most abundant in the different grapes and wines, accounting for 74.94 to 79.70% and 48.60 to 50.62% of total nonanthocyanin phenolics quantified, respectively. Compared to soil tillage, the sward treatments showed a higher content of main mono-phenol and total nonanthocyanin phenolics in grapes and wines. There were significant differences between two cover crop treatments (tall fescue and white clover) and soil tillage for the content of benzoic acid, salicylic acid, caffeic acid, catechin, and total phenolics in the grape berry ( P < 0.05 or P < 0.01). The wine from tall fescue cover crop had the highest gallic acid, caffeic acid and catechin. Cover crop system increased the total nonanthocyanin phenolics of grapes and wines in order of the four treatments: tall fescue, white clover, alfalfa, and soil tillage (control). Cover crop in vineyard increased total phenols of grape berry and wine, and thus improved the quality of wine evidently.