terclim by ICS banner
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

Related articles…

INFLUENCE OF THE NITROGEN / LIPIDS RATIO OF MUSTS ON THE REVELATION OF AROMATIC COMPOUNDS IN SAUVIGNON BLANC WINE

Production of volatile compounds by yeast is known to be modulated by must nitrogen. Nevertheless, various parameter of must quality have an impact on yeast fermentation. In this study we propose to evaluate the impact of nitrogen / lipids balance on a Sauvignon Blanc grape juice (Val de Loire).
Must was prepared from the same grapes at pilot scale. Three modalities were carried out: direct pressing, direct pressing with a pre-fermentation cold stabulation and pellicular maceration before pressing.

Read More

USE OF 13C CP/MAS NMR AND EPR SPECTROSCOPIC TECHNIQUES TO CHARACTERIZE MACROMOLECULAR CHANGES IN OAK WOOD(QUERCUS PETRAEA) DURING TOASTING

For coopers, toasting process is considered a crucial step in barrel production during which oak wood (Q. petraea) develops several aromatic nuances released to the wine during its maturation. Toasting consists of applying different degrees of heat to a barrel for a specific period. As the temperature increases, thermal degradation of oak wood structure produces a huge range of chemical compounds. Many studies have identified the main key aroma volatile compounds (whisky-lactone, furfural, eugenol, guaiacol, vanillin). However, detailed information on how the chemical structure of oak wood degrades with increasing toasting level is still lacking.

Read More

Searching for the sweet spot: a focus on wine dealcoholization

It is well known that the vinification of grapes at full maturation can produce rich, full-bodied wines,
with intense and complex flavour profiles. However, the juice obtained from such grapes may have very
high sugar concentration, resulting in wines with an excessive concentration of ethanol. In addition, the decoupling between technological maturity and phenolic/aromatic one due to global warming, exacerbates this problem in some wine-growing regions. In parallel with the increase of the mean alcohol content of wines on the market, also the demand for reduced alcohol beverages has increased in recent years, mainly as a result of health and social concerns about the risks related to the consumption of alcohol.

Read More

TANNINS AND ANTHOCYANINS KINETICS OF EXTRACTION FROM ARINARNOA, MARSELAN AND TANNAT UNDER DIFFERENT WINEMAKING TECHNIQUES

Marselan wines have an unusual high proportion of seed derived tannins from grapes having high proportions of skins, which are rich in tannins. But the causes behind this characteristic have not yet been identified. In vintage 2023 wines were made at experimental scale (9 kg by experimental unit) from Arinarnoa, Marselan and Tannat Vitis vinifera grape cultivars by traditional maceration, and by techniques aimed to increase the wine content in skin derived tannin: addition of extraction enzymes, addition at vatting of grape-skin enological tannins, or by extended maceration, known to increase the seed derived tannin contents of wines.

Read More

EFFECTS OF WINEMAKING FACTORS AND AGEING ON THE POLYPHENOLIC AND COLORIMETRIC PROFILES IN RED WINES PRONE TO COLOUR INSTABILITY

The effects of (A) grape freezing, and (B) malolactic fermentation, have been evaluated on the chemical and colorimetric profiles of red wines from Schiava grossa cv. grapes, thus prone to colour instability. The aim was to observe if specific variables (e.g. grape freezing) could improve the extraction and stability of pigments. The samples were studied from musts up to twelve months in bottle. The study was conducted with independent parallel micro-vinifications (12 = 4 theses x 3 replicates) under strictly-controlled conditions.

Read More