Macrowine 2021
IVES 9 IVES Conference Series 9 Long-term sensorial and compositional effects of copper fining on the wine containing ‘reductive’ and ‘tropical’ volatile sulfur compounds

Long-term sensorial and compositional effects of copper fining on the wine containing ‘reductive’ and ‘tropical’ volatile sulfur compounds

Abstract

The aim of this study was to investigate long-term sensorial and compositional effects of copper addition to the white wine naturally high in varietal thiol levels, with added volatile sulfur compounds [hydrogen sulfide (H2S) and methanethiol (MeSH)]. The novelty of this study lies in the inclusion of sensory analysis at each time point by using Check-All-That-Apply and Descriptive Analysis methods to evaluate the sensory interaction between ‘reductive’ thiols and tropical thiols after copper fining. The Chenin Blanc wine was used as control (base) wine to which combinations of 40 µg/L H2S and 20 µg/L of MeSH were added, followed by an addition of 0,3 mg/L of copper to selected samples. The wine samples were stored for 24 hours, 6 weeks and 1 year. At each time point chemical analysis of varietal thiols, volatile sulfur compounds and copper levels were performed. The chemical results after 1 year of wine storage, showed a significant increase in the levels of varietal thiol 3-sulfanylhexanol (3-SH) and a decrease of 3-sulfanylhexyl acetate (3-SHA) concentration levels. However, a significant loss of 3-SH occurred in all the copper treated wines after 1 year of storage. On the other hand, the decrease of 3-SHA levels over time was less influenced by copper treatment, but rather due to acid hydrolyses and a subsequent increase in 3-SH (Makhotkina & Kilmartin, 2012). The presence of copper seem to further increase levels of bound- H2S in wine samples, which after 1 year of storage amounted to more than 25 µg/L. Chemical analysis of MeSH showed the significant increase in free and bound MeSH after 1 year of storage in wine samples spiked with MeSH. However, the addition of copper to the MeSH-spiked samples resulted in significant decrease of free and bound MeSH. The most significant sensory impact of the addition of H2S and MeSH to control wine was the suppression effect on “fruitiness” of wine after 24 hours which after 6-weeks and 1-year wine storage period decreased, potentially due to wine matrix absorption of H2S and MeSH (Nikolantonaki & Waterhouse, 2012). Sensory results after 1 year of wine storage showed that “guava”, a “tropical” attribute, was not suppressed with the addition of H2S and MeSH and low doses of “reductive” aromas deriving from H2S and MeSH in wine might even contributed to its sensory perception. Copper additions mainly decreased the perception of “guava” after 1 year. In contrast, the “passionfruit”, also a “tropical” attribute, was slightly suppressed when H2S and MeSH were present. The perception of the ester-derived attributes namely “peach” and “banana” increased in the samples containing copper after 1 year of storage, suggesting that a decrease of the 3-SH varietal thiol due to copper addition may enhance the perception of ester-derived aromas in wine.

DOI:

Publication date: September 14, 2021

Issue: Macrowine 2021

Type: Article

Authors

Matija Lesković

*South African Grape and Wine Research Institute/Department Viticulture and Oenology, University of Stellenbosch, Private Bag X1, Matieland (Stellenbosch) 7602, South Africa,Marlize BEKKER † Jeanne BRAND * Allie KULCSAR † Wessel DU TOIT * *South African Grape and Wine Research Institute/Department Viticulture and Oenology, University of Stellenbosch, Private Bag X1, Matieland (Stellenbosch) 7602, South Africa † The Australian Wine Research Institute, P.O. Box 197, Glen Osmond, South Australia, 5064.

Contact the author

Keywords

varietal thiols, volatile sulfur compounds, wine copper fining, ‘reductive’ and ‘tropical’ volatile sulfur compounds, copper fining and wine storage, wine sensory analysis

Citation

Related articles…

Physiological and growth reaction of Shiraz/101-14 Mgt to row orientation and soil water status

Advanced knowledge on grapevine row orientation is required to improve establishment, management and outcomes of vineyards on terroirs with different environmental conditions (climate, soil, topography) and in view of a future change to more extreme climatic conditions. The purpose of this study was to determine the combined effect of row orientation, plant water status and ripeness level on the physiological and viticultural reaction of Shiraz/101-14 Mgt.

Effects of mechanical leafing and deficit irrigation on Cabernet Sauvignon grown in warm climate of California

San Joaquin Valley accounts for 40% of wine grape acreage and produces 70% of wine grape in California. Fruit quality is one of most important factors which impact the economical sustainability of farming wine grapes in this region. Due to the recent drought and expected labor cost increase, the wine industry is thrilled to understand how to improve fruit quality while maintaining the yield with less water and labor input. The present study aims to study the interactive effects of mechanical leafing and deficit irrigation on yield and berry compositions of Cabernet Sauvignon grown in warm climate of California.

The effects of cane girdling on berry texture properties and the concentration of some aroma compounds in three table grape cultivars

The marketability of the table grapes is highly influenced by the consumer demand; therefore the market value of the table grapes is mainly characterized by its berry size, colour, taste and texture. Girdling could cause accumulation of several components in plants above the ringing of the phloem including clusters and resulting improved maturity. The aim of the experiments was to examine the effect of girdling on berry texture characteristics and aroma concentration.

Application of a fluorescence-based method to evaluate the ripening process and quality of Pinot Blanc grape

The chemical composition of grape berries at harvest is one of the most important factors that should be considered to produce high quality wines. Among the different chemical classes which characterize the grape juice, the polyphenolic compound, such as flavonoids, contribute to the final taste and color of wines. Recently, an innovative non-destructive method, based on chlorophyll fluorescence, was developed to estimate the phenolic maturity of red grape varieties through the evaluation of anthocyanins accumulated in the berry skin. To date, only few data are available about the application of this method on white grape varieties.

Different yield regulation strategies in semi-minimal-pruned hedge (SMPH) and impact on bunch architecture

Yields in the novel viticulture training system Semi-Minimal-Pruned Hedge (SMPH) are generally higher compared to the traditional Vertical Shoot Positioning (VSP). Excessive yields have a negative impact on the vine and wine quality, which can result in substantial losses in yield in subsequent vintages (alternate bearing) or penalties in fruit quality. Therefore yield regulation is essential. The bunch architecture in SMPH differs from VSP. Generally there is a higher amount but smaller bunches with lower single berry weights in SMPH compared to VSP.