A range of structurally defined apple and grape proanthocyanidins was isolated in sufficient amount to carry out a formal sensory descriptive analysis study. Purified proanthocyanidin fractions differed in chain length, degree of galloylation and epigallocatechin content. Astringency attributes of the preparations in a model wine medium were rated while the fractions were held in the mouth and after expectoration. The degree of polymerization appeared to be the variable that discriminated among the fractions to the greatest extent. It affected both the overall astringency and the different individual astringency attributes, with increased 'drying', 'chalky', 'adhesive' and 'pucker' characters correlating with increasing chain length. A rougher sensation with increased 'coarseness', 'drying' and 'chalkiness' correlated with an increased degree of galloylation of the fractions. The presence of epigallocatechin units in the proanthocyanidin tended to lower the 'coarse' perception.

The value of, opportunities provided by, and the difficulties in elucidating the exact contribution that chemical compounds make to wine aroma and flavour are outlined and highlighted in this review. This paper provides an overview of the current understanding of relationships between wine sensory properties and volatile chemical composition through a discussion of recent studies where accurate, precise chemical data have been obtained for compounds shown by quantitative gas chromatography‐olfactometry (GC/O) to be odour active in a sample. A centrepiece of this discussion is a compilation of compounds indicated to be most important to wine aroma. This is followed by a consideration of the limitation of odour activity values obtained by GC/O with particular reference to wine esters and volatile thiol compounds. The strengths of sensory descriptive analysis and its associated statistical methodologies to complement chemical composition data for aroma compounds are also explored. Grape flavour precursor compounds and the development of methods for their rapid quantification are then discussed in the context of the role of precursors contributing to wine aroma. Finally, an assessment is given of the likelihood in the near future of developing analytical strategies to measure wine flavour in relation to consumer expectations on the one hand, and on the other, to viticultural management practices to influence grape flavour composition.

The aim of this study was to determine how changes in grape composition brought about by artificial shading (sunlight exclusion) influence wine properties including colour, flavonoid composition and sensory attributes. Prior to flowering, bunches of Shiraz grapes were enclosed in boxes designed to eliminate light without altering bunch temperature and humidity. This artificial bunch shading had little effect on berry ripening and accumulation of sugar but at harvest the shaded bunches had smaller berries and higher seed weight, juice pH and titratable acidity. The amount of anthocyanins in the fruit was not changed significantly but anthocyanin composition in the shaded berries was shifted towards dioxygenated anthocyanins (the glucosides of cyanidin and peonidin derivatives). Shaded fruit had increased seed tannins and decreased skin tannins but the largest relative change in flavonoids was a marked decrease in flavonols in the shaded fruit, similar to previous studies. Wines made from shaded fruit had lower wine colour density, total phenolics, anthocyanins and tannins when the wine was bottled and after ageing for up to three years. Analysis of potential flavour compounds following acid hydrolysis indicated that the wines made from shaded fruit had decreased levels of glycosides of β‐damascenone and 1,1,6‐trimethyl‐1,2‐dihydronaphthalene (TDN). Sensory analysis of the wines indicated no significant difference in aroma attributes but the wines made from shaded fruit were rated lower for astringency, fruit flavour and flavour persistence in‐mouth sensory attributes. The results indicate that extreme shading of Shiraz fruit can decrease wine colour, anthocyanins and tannins as well as altering sensory attributes.

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