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IVES 9 IVES Conference Series 9 ‘TROPICAL’ POLYFUNCTIONAL THIOLS AND THEIR ROLE IN AUSTRALIAN RED WINES

‘TROPICAL’ POLYFUNCTIONAL THIOLS AND THEIR ROLE IN AUSTRALIAN RED WINES

Abstract

Following anecdotal evidence of unwanted ‘tropical’ character in red wines resulting from vineyard interventions and a subsequent yeast trial observing higher ‘red fruit’ character correlated with higher thiol concentrations, the role of polyfunctional thiols in commercial Australian red wines was investigated.

First, trials into the known tropical thiol modulation technique of foliar applications of sulfur and urea were conducted in parallel on Chardonnay and Shiraz.1 The Chardonnay wines showed expected results with elevated concentrations of 3-sulfanylhexanol (3-SH) and 3-sulfanylhexyl acetate (3-SHA), whereas the Shiraz wines lacked 3-SHA. Furthermore, the Shiraz wines were described as ‘drain’ (known as ‘reductive’ aroma character) during sensory evaluation although they did not contain thiols traditionally associated with ‘reductive’ thiols (H2S, methanethiol etc.).

Secondly, a survey of over 100 commercial Australian red wines across 10 different varieties supported the outcome of the foliar application trial.2 While all red wines contained 3-SH above the sensory detection threshold (60 ng/L, aqueous ethanol), no wines were observed to contain detectable concentrations of 3-SHA. As such, the acetylation of 3-SH to 3-SHA in red wine fermentations appears to be extremely limited.

Lastly, 3-SH and/or 3-SHA were spiked into four different varieties of red wine to understand the impact on sensory attributes.2 Traditionally lighter varieties (Pinot Noir and Grenache) had increased ‘red fruit’ and ‘lolly’ ratings at low concentrations of 3-SH and 3-SHA but changed to ‘tropical’ at higher concentrations. For Cabernet Sauvignon, 3-SH and 3-SHA additions resulted in increases to ‘blackcurrant’ and ‘tropical’ attributes, whereas Shiraz additions of 3-SH resulted in ‘sweaty’ and ‘tropical’ descriptors.

The ‘tropical’ thiol, 3-SH, was ubiquitous in Australian red wines although the acetylation to 3-SHA was not commonly observed. The impact of these thiols in red wines differed by variety, and their presence was increased by vineyard foliar application treatments. As such, vineyard management practises might hold the key to avoiding undesirable expressions of ‘tropical’ characters in red wine.

 

1. Cordente, A. G.; Curtin, C. D.; Solomon, M.; Kulcsar, A. C.; Watson, F.; Pisaniello, L.; Schmidt, S. A.; Espinase Nandorfy, D. Modulation of volatile thiol release during fermentation of red musts by wine yeast. Processes 2022, 10 (3), 502.
2. Hixson, J.; Bilogrevic, E.; Capone, D.; Nandorfy, D. E.; Francis, L.; Petrie, P.; Solomon, M.; Krstic, M. AWRI report: Enhancing tropical fruit flavour in Chardonnay and Shiraz through foliar nutrient sprays. Wine & Vitic. J. 2020, 35 (3), 30-33. 
3. Siebert, T.; Francis, L.; Pisaniello, L.; Melzer, S.; Bey, L.; Watson, F.; Espinase Nandorfy, D.; Cordente, T. Do varietal thiols matter in red wine? AWRI Tech. Rev. 2019, 243, 10-15.

DOI:

Publication date: February 9, 2024

Issue: OENO Macrowine 2023

Type: Article

Authors

Tracey Siebert1, Mark Solomon1, Lisa Pisaniello1, Damian Espinase Nandorfy1,2, Eleanor Bilogrevic1, Flynn Wat-Son1, Toni Cordente1, Leigh Francis1, Josh Hixson1

1. The Australian Wine Research Institute, Waite Precinct, Hartley Grove cnr Paratoo Road, Urrbrae 5064, Australia.
2. CASS Food Research Centre, School of Exercise and Nutrition Sciences, Deakin University, 221 Burwood Highway, Burwood, VIC, 3125, Australia.

Contact the author*

Keywords

red wine, ‘tropical’ aroma, thiols, sensory

Tags

IVES Conference Series | oeno macrowine 2023 | oeno-macrowine

Citation

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