 IVES 9 IVES Conference Series 9 The temporal sensory interaction between 3-Mercaptohexanol, 3-Mercaptohexyl Acetate and Athanethiol using trata

The temporal sensory interaction between 3-Mercaptohexanol, 3-Mercaptohexyl Acetate and Athanethiol using trata

Abstract

Volatile sulphur compounds are a group of impact odorants with low odour thresholds that can contribute both positively and negatively to wine aroma. The varietal thiols, 3MH and 3MHA, are known to contribute positive tropical aromas to white wines and are most abundant in Sauvignon Blanc wines. The group of compounds contributing negative aromas are known as reductive sulphur compounds (RSCs) as they add a reductive aroma of asparagus, cooked vegetables and rotten egg to wines. All these compounds play a part in and are a result of the sulphur pathway in the yeast cell during fermentation and therefore attempting to increase the concentration of the varietal thiols may directly influence the concentration of the RSCs. The varietal thiols and the low molecular weight RSCs are highly volatile and therefore their sensory perception can change rapidly over time.

AIM: The aim of this study was to investigate the sensory interaction between varietal thiols and fermentative RSCs in wine for the first time.

METHODS: The varietal thiols 3MH and 3MHA; and ethanethiol (EtSH), a RSC, were spiked in a model wine solution and evaluated sensorially using temporal rate-all-that-apply (TRATA). TRATA is a novel method for temporal sensory evaluation of products. It allows for the free concurrent quantification of the intensity of multiple attributes by the sensory panellists. The panel consisted of staff and students of Stellenbosch University that were familiar with the sensory evaluation of varietal thiols in wine. The levels used for 3MH (500 and 2500 ng/L) and 3MHA (100 and 400 ng/L) in this study were based on low and high concentrations as found in commercial South African Sauvignon Blanc wines. The EtSH levels were based on the odour threshold (1 µg/L) and a level at which wines are considered faulty (2.5 µg/L).

RESULTS: The study showed that the positive aromas associated with 3MH and 3MHA can be suppressed by EtSH in certain situation and three-way interactions were found for specific attributes. The negative aromas associated with EtSH show no significant interactions with varietal thiols although 3MH alone can exhibit a reductive aroma. Time plays a significant role in the perception of these sulphur compounds and certain interactions only occur 60-120s after the start of the sensory evaluation.

CONCLUSIONS:

Reductive sulphur compounds can significantly suppress the aromas of the varietal thiols 3MH and 3MHA.

DOI:

Publication date: September 24, 2021

Issue: Macrowine 2021

Type: Article

Authors

Sebastian Vannevel, Jeanne BRAND, Astrid BUICA, Wessel DU TOIT,

South African Grape and Wine Research Institute, Department of Viticulture and Oenology, Stellenbosch University, South Africa

Contact the author

Keywords

varietal thiols, reductive sulphur compounds, trata (temporal rate-all-that-apply), aroma interaction study

Citation

Sustainable fertilisation of the vineyard in Galicia (Spain)

Excessive fertilization of the vineyard leads to low quality grapes, increased costs and a negative impact on the environment. In order to establish an integrated management system aimed at a sustainable fertilization of the vineyards, nutritional reference levels were established. For this purpose, 30 representative vineyards of the Albariño variety were studied, in which soil and petiole analyses were carried out for two years and grape yield and quality at harvest were measured. In both years of study, soil pH, calcium, sodium and cation exchange capacity were positively correlated with calcium content and negatively correlated with manganese in grapes. Irrigated vineyards had higher levels of aluminium in soil and lower levels of calcium in petiole. Climatic conditions were very different in the years of the study. The year 2019 was colder than usual, in 2020 there was a marked water stress with high summer temperatures. This resulted in medium-high acidity in grapes in 2019 and low acidity in 2020, with sugar levels being similar both years. A very marked decrease in must amino nitrogen was observed in 2020, with ammonia nitrogen remaining stable. The correlation of acidity and sugar values in grapes with soil and petiole analysis data made it possible to establish reference levels for the nutritional diagnosis of the Albariño variety in this region. Based on these results, an easy-to-use TIC application is currently being created for grapegrowers, aimed at improving the sustainability of the vineyard through reasoned fertilization. This study has now been extended to other Galician vine varieties.

PINKING PHENOMENA ON WHITE WINES: RELATION BETWEEN PINKING SUSCEPTIBILITY INDEX (PSI) AND WINE ANTHOCYANINS CONTENT

Pinking is the emergence of pink tones in white wines exclusively produced from white grape varieties, known as pinking phenomena for many years. Pinking is essentially appeared when white wines are produced under reducing conditions [1,2,3]. Pinking usually occurs after bottling and storage of white wines, but its appearance has also been described after alcoholic fermentation or even as soon as the grape must is extracted [4]. Therefore, the purpose of this work was to investigate the existence of an-thocyanins in white wines made from different white grape varieties and grown locations and critically evaluate the most common method used for predicting pinking appearance in white wines: the Pinking Susceptibility Index (PSI).

Zoning mountain landscapes for a valorisation of high identity products

Mountain agriculture is made difficult by the geomorphological complexity of the territory. This is especially true for viticulture: over the centuries the work of men in such a difficult environment

Changes in grape-associated microbiome as a consequence of post-harvest withering

AIM: Grape withering is an oenological post-harvest process used for production of reinforced and sweet wines. Drying can be carried out by keeping the ripe grape in traditional large, well-aired rooms (non-controlled environment) or, more and more often, in a warehouse under controlled conditions of airflow and relative humidity (controlled environment)[1].

Tracing glycosidically-bound smoke taint markers from grape to wine

The increasing frequency of wildfires on the West Coast of the USA is seen as a significant risk for the grape and wine industry. Research has shown that perceived smoke impact in wines correlates with increases in volatile phenols (VPs) in grapes exposed to fresh smoke.