S-Cysteinylated and S-glutathionylated thiol precursors in grapes. A review

Non-volatile thiols derivated from cysteine and glutathione are precursors of the most powerful aroma compounds existing in nature. Volatile thiol compounds are naturally present in grapes, and they are released after fermentation, giving wines many desired properties. However, the amount in which they are found in grapes is small (ng/l), so sensitive techniques are needed to quantify them. Nowadays, High Performance Liquid Chromatography–Mass Spectrometry is the more widely used technique, which does not need the derivatization of the compounds. Studies to identify, quantify and find out the way these compounds are released have only been carried out during the last two decades. This review contains an overview of the field and brief description of the most important of these studies.