Measuring Thiols in Single Cultivar South African Red Wines Using 4,4-Dithiodipyridine (DTDP) Derivatization and Ultraperformance Convergence Chromatography-Tandem Mass Spectrometry.

Mpho Mafata,Baptiste Thomachot,Maria Stander,Astrid Buica

doi:10.3390/foods7090138

Abstract

Wine varietal thiols are important contributors to wine aroma. The chemical nature of thiols makes them difficult to measure due to low concentrations, high sensitivity to oxidation, and low ionization. Methods for the measurement of thiols usually consist of multiple steps of sample preparation followed by instrumental measurement. Studies have collected large datasets of thiols in white wine but not in red wine, due to the lack of availability of suitable methods. In this study, for the first time, convergence chromatography was used to measure thiols in red wine at ultratrace levels with improved sensitivity compared to previous methods. Performance parameters (selectivity, linearity, limits of detection, precision, accuracy) were tested to demonstrate the suitability of the method for the proposed application. Red wine thiols were measured in South African Pinotage, Shiraz, and Cabernet Sauvignon wines (n = 16 each). Cultivar differentiation using the thiol profile was demonstrated.

Highlights

The volatile fraction of wine is arguably the most important contributor to wine aroma and flavor
Thiol compounds derived from grape precursors, fermentation, and postfermentation/aging treatments provide some important and desirable flavor attributes to both red and white wines [1,2]
All prepared solutions are expressed in terms of volume percent (%, v/v), with the balance composed of Milli-Q water, unless otherwise specified

Summary

Introduction

The volatile fraction of wine is arguably the most important contributor to wine aroma and flavor. Thiol compounds derived from grape precursors, fermentation, and postfermentation/aging treatments provide some important and desirable flavor attributes to both red and white wines [1,2]. 4-MMP is associated with “black currant” in French red blends [2] and furanmethanethiol (FMT) with “coffee” descriptors [4,5]. Measurement of these wine thiols commonly includes an extensive sample preparation step where the thiols can be extracted free [6], bound using a mercury-based chelator [7,8], or chemically modified using a derivatizing agent [1,9,10].

Methods

Discussion

Conclusion