Potential grape-derived contributions to volatile ester concentrations in wine.

Paul Boss,Emily Nicholson,Anthony Pearce,David Jeffery,Eric Dennis,Yanjia Zhao

doi:10.3390/molecules20057845

Abstract

Grape composition affects wine flavour and aroma not only through varietal compounds, but also by influencing the production of volatile compounds by yeast. C9 and C12 compounds that potentially influence ethyl ester synthesis during fermentation were studied using a model grape juice medium. It was shown that the addition of free fatty acids, their methyl esters or acyl-carnitine and acyl-amino acid conjugates can increase ethyl ester production in fermentations. The stimulation of ethyl ester production above that of the control was apparent when lower concentrations of the C9 compounds were added to the model musts compared to the C12 compounds. Four amino acids, which are involved in CoA biosynthesis, were also added to model grape juice medium in the absence of pantothenate to test their ability to influence ethyl and acetate ester production. β-Alanine was the only one shown to increase the production of ethyl esters, free fatty acids and acetate esters. The addition of 1 mg∙L−1 β-alanine was enough to stimulate production of these compounds and addition of up to 100 mg∙L−1 β-alanine had no greater effect. The endogenous concentrations of β-alanine in fifty Cabernet Sauvignon grape samples exceeded the 1 mg∙L−1 required for the stimulatory effect on ethyl and acetate ester production observed in this study.

Highlights

Wine is a complex solution containing abundant volatile compounds which contribute to wine aroma and flavour, and impact wine quality and appreciation
Odd-numbered fatty acids and their ethyl esters are found in low abundance in wine, meaning that it is easier to follow the effect of the addition of odd-numbered potential precursors on ethyl ester production as the endogenous concentrations are low
medium chain fatty acids (MCFAs), their methyl esters and carnitine conjugates were able to contribute to ethyl ester production, albeit with variable influences of odd and even chain length MCFAs

Summary

Introduction

Wine is a complex solution containing abundant volatile compounds which contribute to wine aroma and flavour, and impact wine quality and appreciation. The volatile composition of most wines, or styles of wine, is very similar, and the varietal differences that exist between wines made from different varieties of grapes are largely due to the relative ratios of the volatile compounds contained within [3]. The types of volatile compounds are diverse, and include esters, higher alcohols, aldehydes, ketones, lactones, acids, phenols, N-heterocycles, isoprenoids and sulfur compounds [1,4]. Of these categories, higher alcohols represent the largest volatile pool in terms of concentration, but esters have the largest number of contributing molecules [5]

Objectives

Results

Conclusion