The impact of postharvest ultra-violet light irradiation on the thiol content of Sauvignon blanc grapes

Abstract

Sauvignon blanc grapes were exposed to an ultra-violet (UV) light source post-hand harvest (whole bunches) or post-machine harvest. The thiol precursors S-3-(hexan-1-ol)-l-cysteine (Cys-3MH) and S-3-(hexan-1-ol)-l-glutathione (GSH-3MH) were quantified in the juices before and after UV treatment. Results showed that irradiation of the grapes with UV light had little to no effect on the thiol precursors. Wines were fermented from the corresponding juices and 18 aroma compounds were quantified. Differences were found between UV treatments of the wines for 3-mercaptohexanol, hexan-1-ol, ethyl butanoate, ethyl hexanoate, ethyl octanoate and phenylethyl alcohol. However, these changes were not significant (p < 0.05) for both grape media trialled. Future studies involving larger sample sizes and replicate numbers should be completed in order to ascertain any changes in aroma chemistry as a result of UV light application to grapes postharvest.

Keywords: 3-Mercapto hexylacetate; 3-Mercaptohexanol; Postharvest; Thiol precursor; Ultra-violet.