Influence of foliage-sprayed zinc sulfate on grape quality and wine aroma characteristics of Merlot

Abstract

Three concentrations of zinc sulfate were foliage-sprayed in Vitis vinifera cv. Merlot growing on Zn-deficient soils over successive years, 2013 and 2014, to investigate the effect on grape quality and wine aroma characteristics. Headspace solid-phase microextraction with gas chromatography–mass spectrometry (HS-SPME-GC/MS) was used for qualitative and quantitative analysis of aroma compounds. Zinc sulfate treatments significantly increased the concentrations of total soluble solids, total phenols, flavonoids, flavanols, tannins and anthocyanins in matured berry. A total of 53 compounds were identified and quantified from all the eight wines of the 2 years. Zinc sulfate treatments increased the variety of volatile compounds in wines, especially in the aged wines of 2013. Besides, total concentration of the volatile compounds was also enhanced by treatment of 4.0 g/L ZnSO4·7H2O in both years. Principal component analysis indicated that 1-nonanol, 1-butanol-3-methyl acetate, ethyl hexanoate, ethyl phenylacetate, ethyl benzoate, ethyl palmitate, p-hydroxyl ethyl cinnamate and β-damascenone were the eight most characteristic components of Zn-treated wines in both 2013 and 2014. Among those, β-damascenone and ethyl hexanoate were also two of the most odor-active compounds. Moreover, among the nine described aroma categories in the sensory analysis, intensities of fruity, vegetative, spicy, nuts and toasty were influenced by Zn treatment.