Flavonoids and C13-norisoprenoids in Vitis vinifera L. cv. Shiraz: relationships between grape and wine composition,wine colour and wine sensory properties

Background and Aims: This study investigated flavonoid composition and C₁₃-norisoprenoids (β-damascenone and β-ionone) in Shiraz grapes and wines, their relationships and links to wine sensory properties. Methods and Results: Differences in the grape berry flavonoid profile were created by exposing bunches to varying levels of sunlight intensity through canopy manipulation. Grapes were harvested at similar maturity and three replicate wines were made for each treatment in both vintages. Grapes produced under shaded canopy conditions had reduced anthocyanins and skin tannins, but little effect on seed tannins was observed. Pigmented polymers and tannins in wines were related to berry flavonoid composition (anthocyanins, skin and seed tannins, and their ratios). In grapes and wines, no significant effects were observed in response to canopy manipulation for two hydrolytically released C₁₃-norisoprenoids, β-damascenone and β-ionone. Relationships were established for wine flavonoid composition, wine colour density, sensory perception of the astringency-related mouth-feel attributes and a quality scale. A positive relationship between wine quality score and hydrolytically released β-damascenone in both berries and wines was found, but not for free β-damascenone or any quantified forms of β-ionone. Conclusion: Higher concentrations of anthocyanins and skin tannins in berries, coupled with a lower concentration of seed tannins were associated with higher wine quality. The ratio anthocyanins*skin tannins/seed tannins is proposed as an indicator of wine flavonoid composition, wine colour and wine quality. Excessive canopy shade was detrimental to berry and wine composition and intensified sensory detection of ‘straw’ and ‘herbaceous’ characters in the wines. Significance of the Study: This study increases the understanding of the balance and composition of flavonoid compounds and C₁₃-norisoprenoids in berries and their relationship with wine composition and wine sensory properties, but also highlights the importance of a canopy microclimate assessment.     

The effect of bunch shading on berry development and flavonoid accumulation in Shiraz grapes

Opaque boxes were applied to bunches of Shiraz grapes prior to flowering to determine the effect of sunlight on berry development and accumulation of flavonoids. The boxes were designed to maintain airflow while excluding light and thus to minimise changes in temperature and humidity. There was no significant effect of shading on sugar accumulation and in two of the three seasons studied there was no effect on berry weight. Chlorophyll concentration was much lower in the shaded fruit, which appeared pale yellow until veraison. The fruit coloured normally in the shaded bunches and in two of the three seasons there was no significant change in anthocyanin content. Expression of the gene encoding UDP-glucose flavonoid-3-O-glucosyl transferase (UFGT), a key gene in anthocyanin synthesis, increased after veraison and was similar in both shaded and exposed fruit. Anthocyanin composition was altered in the shaded fruit, which had a greater proportion of the dioxygenated anthocyanins, the glucosides of cyanidin and peonidin. Shading had no significant effect on the levels of condensed tannins in the skin or seeds of ripe fruit. Shading significantly reduced the levels of flavonols in the grape skin. In the exposed fruit, flavonol concentration was highest around flowering then declined as the berries grew, but there was an increase in flavonols per berry during ripening. When the boxes were applied before flowering, shaded fruit had much lower levels of flavonols throughout berry development and at harvest the level of flavonols were less than 10% of that in exposed fruit. A gene encoding flavonol synthase (FLS) was expressed at flowering and during ripening in exposed grapes but its expression was greatly reduced in shaded fruit. The results indicate that shading had little effect on berry development and ripening, including accumulation of anthocyanins and tannins, but significantly decreased flavonol synthesis.     

Canopy microclimate and berry composition: The effect of bunch exposure on the phenolic composition of Vitis vinifera L cv. Shiraz grape berries

Studies on the effect of light exposure on specific phenolic compounds of berries from Shiraz vines grown in a hot climate are reported. Berries that had developed on bunches receiving high levels of ambient light generally had the highest relative levels of quercetin-3-glucoside and a lower proportion of their malvidin anthocyanins as the coumarate derivative, compared to berries that had developed on bunches in shaded canopy conditions. The response of total anthocyanin levels to treatment conditions was variable and depended on the degree of bunch shading and the resultant berry temperature. It appears that a high degree of bunch exposure in hot climates is not conducive to optimal anthocyanin accumulation in berries. The interactive effects of light and temperature on berry phenolic content and concentration are discussed.     

The aroma of Muscat of Frontignan grapes: effect of the light environment of vine or bunch on volatiles and glycoconjugates

Effects of the modification of whole vine or individual cluster light environment by shade cloth from berry set to maturity were studied on the volatiles and glycoconjugates in Muscat (Muscat of Frontignan; Vitis vinifera L) berries over 2 years. Whole vines were shaded with 50 and 70% shade cloth, while bunches were shaded with 90% shade cloth. The sun‐exposed berries were chosen as control berries, and the berries naturally shaded under foliage were also studied. The natural shading of bunches under foliage did not decrease the levels of free and bound compounds in Muscat berries compared to sun‐exposed berries. The artificially shaded bunches showed lower levels of monoterpenols and C13 norisoprenoids than sun‐exposed berries and berries from naturally shaded bunches. Moreover, the effect of vine shading on the aroma composition of Muscat berries was lower compared to artificial bunch shading. In 1996 the leaf area/fruit yield ratio was modified by decreasing the bunch number per vine. This change did not influence the total amounts of glycosidically bound compounds, except for monoterpenic glycoconjugates. However, the higher monoterpenic glycoconjugate levels in these berries were likely related to their early maturity. Under our experimental conditions, berry aroma composition did not appear to be affected by foliage shade. © 2000 Society of Chemical Industry     

Relationships between berry size,berry phenolic composition and wine quality scores for Cabernet Sauvignon (Vitis vinifera L.) from different pruning treatments and different vintages

Background and Aims: Commercial winemakers observed differences in wine sensory properties among wines produced from vines of three different pruning treatments in a single vineyard. To clarify the relationships between berries and wine quality, this study examined berry size and berry composition and the quality rating for wines produced from the pruning treatments. Methods and Results: The study was conducted over three seasons. Berries from Machine‐, Cane‐ and Spur‐pruned vines were sampled at commercial harvest for analysis of berry size and berry phenolic composition. Wines made from each treatment were assessed for quality by a panel of winemakers. Machine berries were lighter and had higher concentrations of anthocyanins, tannins and total phenolics than Cane or Spur. Machine wines had the lowest quality scores. Comparing vintages, berries from 2004 were lighter, but did not always differ in phenolic composition to other vintages, and wines from 2004 had lower quality scores than the other vintages. Vintage effects were generally stronger than pruning effects. Conclusions: In this study, high berry anthocyanins, total phenolics and tannin concentration measures were not good indicators of wine quality scores. Changes in vineyard treatments and, in particular, vintage influences, produce incremental, but potentially important, changes to berry size and composition and to wine quality. Significance of the Study: This study is unique in its focus on the commercial reality of producing wines to a specific style and quality, while bringing scientific rigour to investigating the relationships between berries and wine quality in this vineyard over a number of vintages.     

Effects of the rootstock Ramsey (Vitis champini) on ion and organic acid composition of grapes and wine, and on wine spectral characteristics

The influence of Ramsey, used as rootstock of the scion cvs Muscat Gordo Blanco (syn. Muscat of Alexandria), Shiraz (syn. Syrah), Riesling, Cabernet Sauvignon and Chardonnay, on the characteristics of the grape berries and of wine made from them was investigated, comparing ‘own-rooted’ and ‘grafted’, and comparing wine fermented as juice (without skins) and must (juice and skins). The study involved the partitioning of K+ within berries, changes in juice K+, malic and tartaric acid through fermentation, wine inorganic ion and organic acid composition, and wine spectral characteristics. K+ concentration was higher in berries from grafted than from own-rooted for all varieties except Chardonnay, and highest for grafted Shiraz. It was higher in skin than in pulp and seeds. In the pulp, it was highest for grafted Shiraz. K+ concentrations in all ferments using must (i.e. juice plus skins) increased during the initial two days after crushing, with the increase reflecting extraction from skins, being greatest for Shiraz and Muscat Gordo Blanco. Tartaric acid concentration in must also increased during the initial two days after crushing and then decreased. Malic acid concentration was higher in juice of Ramsey-grafted than own-rooted vines, especially for Shiraz; concentrations did not change markedly during the initial 12 days of fermentation, except where malo-lactic fermentation occurred. Wine made from grapes of grafted contained significantly less tartaric and more malic acid than that made from own-rooted for all varieties and for both fermentation types, with the exception of tartaric acid in wine of Muscat Gordo Blanco fermented as must. Wine made from juice had significantly higher tartaric acid and lower malic acid than that made from must for all varieties except for tartaric acid in wine from grafted Shiraz and malic acid in own-rooted Chardonnay. Wine had a smaller tartaric acid/malic acid ratio when made from must. Wine pH was positively correlated with K+ but negatively with tartaric acid and with the tartaric acid to malic acid ratio. Overall, Shiraz wine contained highest Cl?, Na+ and K+ concentrations. Red wines obtained from grafted had higher colour hue, especially those from Shiraz. Wines made from fruit borne on own-rooted Cabernet Sauvignon had the highest concentration of total anthocyanins, ionised anthocyanins and total phenolics.     

Variation in Shiraz berry size originates before fruitset but harvest is a point of resynchronisation for berry development after flowering

Background and Aims:  Asynchronous berry development results in variation in berry size and berry composition. Variation in berry size affects vineyard yield, wine quantity and berry composition, while variation in berry composition affects fruit flavour and wine quality. The objective of this study is to identify when variation in berry size begins.
Methods and Results:  Shiraz bunches were sampled at seven stages throughout the growing season and the development of individual berries was characterised by measurements of weight, volume, surface area, deformability, seed number and seed weight. Coefficients of variation with respect to berry weight, volume and surface area were elevated throughout the post-flowering period but declined as the berries approached harvest ripeness.
Conclusions:  Variation in berry size originates prior to berry set, most probably during differentiation in the floral primordium at budburst. Harvest represents a point of resynchronisation in berry development when a number of physiological changes become synchronised between berries and within the bunch.
Significance of the Study:  Variation in berry size is presumed by the wine industry to have a negative impact on crop level, fruit composition and wine quality. Much of this presumption is scientifically unsubstantiated. The findings of this paper should encourage grapegrowers and winemakers to modify the timing of the harvest to coincide with a reduction in variation in berry size.     

Impact of chemical profile on sensory evaluation of tropical red wines

This study evaluated the correlation between the chemical composition of red wines and the sensory perception of the products. The visual, gustatory and flavour attributes of eight samples of tropical red wines were characterised by semi-trained panellists using the check-all-that-apply methodology. Titratable and volatile acidity, pH, contents of ethanol, total polyphenols and anthocyanins, and the chromatic parameters of the red wine samples were determined. The analysis of the correlations between visual attributes and sensory perception indicated that the evaluation of the wine colour attributes can predict other sensory characteristics related to aromas and flavours. This enabled the wine tasters to distinguish subtle variations in the visual attributes of the product. The results of this study indicated that panellists who underwent short-term training can sensorially perceive the influence of physicochemical variables on wine quality. Additionally, the correlation analysis enabled the identification of production adjustments and the understanding of the consumer perception of a complex product.     

Effect of Colletotrichum acutatum ripe rot on the composition and sensory attributes of Cabernet Sauvignon grapes and wine

Background and Aim:  The impacts of the fungal bunch rot pathogen Colletotrichum acutatum (ripe rot) on grape growing are documented; however, little is known about how the disease affects the resulting wine. This work aimed to investigate how ripe rot affects wine composition and sensory properties.
Methods and Results:  Wine was made using Cabernet Sauvignon grapes grown in the Hastings Valley (NSW). Berries with ripe rot tended to shrivel and acquired a distinctive off flavour and bitterness, described as hessian sack and musty. Wine made from the infected fruit had a higher pH and a higher level of residual sugar, but lower titratable acidity. Volatile acidity in wine made from uninfected fruit was 0.57 g/L, but increased to 0.83 and 1.06 g/L with 1.5 and 3% infection, respectively. Wine made from infected fruit had higher levels of both glycerol and gluconic acid indicative of fungal contamination. Alcohol concentration was also higher in wine made from infected fruit. Sensory analysis indicated that wine made from as low as 3% infected fruit had a similar colour density to control fruit, but a distinctive off-flavour, and browner colour hue.
Conclusions:  As far as we are aware of, this is the first report of a correlation between the level of grape infection by C. acutatum and wine composition in Australia.
Significance of the Study:  These results underline the problems of red grapes infected with C. acutatum . It provides viticulturists and winemakers with information to be considered when assessing grape quality and winemaking process for red wines.     

Biosynthesis of flavour compounds in Muscat Gordo Blanco grape berries

Inflorescences of the floral grapevine cv Muscat Gordo Blanco (syn. Muscat of Alexandria) were grown on their own shoots until maturity or, after approach-grafting before flowering, on the shoots of the non-floral cv Shiraz (in the glasshouse) or Sultana (in the field). The flavour compounds of their berries were compared with those in the berries of the non-floral cultivars, grown either on their own shoots or, by grafting, on the shoots of the Muscat cultivar. For this, monoterpene glycosides were isolated from the fruits, enzymatically hydrolysed and the released monoterpene aglycons were liquid-liquid extracted and analysed by GC-MS. The Muscat Gordo Blanco berries of ungrafted bunches and of bunches grafted onto Shiraz or Sultana vines yielded fruit with monoterpenes at levels and types typical of this floral grape variety. The berries of Shiraz and Sultana bunches contained only low levels of monoterpene glycosides both on their own shoots or grafted onto Muscat shoots. The lack of difference between flavour compounds in grafted and non-grafted fruit indicate that aroma compounds are synthesised in the berries and that their presence is determined by the genotype of the grape bunch rather than by the genotype of the vine.     

Dependence of wine sensory attributes on vine water status

The dependence of wine sensory attributes on the water status of the source vines was determined following vineyard irrigation treatments which included early and late season water deficits and continually irrigated vines. In both seasons, the experimental wines made from the different irrigation treatments did not differ in the concentration of residual sugar or ethanol, titratable acidity, or pH. The concentrations of anthocyanins and total soluble phenolics in the wines were greater from water deficit treatments than from continually irrigated vines. For sensory evaluation, a novel protocol for paired comparisons was developed to test separately for differences in wine appearance, flavour, taste and aroma; differences were detected for each wine comparison. In both seasons, continually irrigated wine differed from early and late season water deficit wine, and early season water deficit wine differed from late season water deficit wine in appearance, flavour, taste and aroma. The sensory differences were not attributable to differences in vine yield or fruit maturity. When professional wine tasters were sampled using similar tests, a majority was able to detect visual but not flavour differences between a selected pair of wines. It is concluded that, where vine water status can be altered, irrigation offers a means to manipulate wine sensory characteristics in the vineyard.     

The impact of over‐maturation on the sensory and nutritional quality of Gouqi (Chinese wolfberry) wine

This study compared the nutritional quality and sensory attributes of wine made from dried Gouqi berries that were mature (NDG), mildly over‐matured (MDG) and severely over‐matured (SDG). Whilst these wines had the similar physicochemical properties, the MDG wine possessed higher polysaccharide levels, whereas the highest total flavonoids were found in the NDG wine. A slight difference in the amino acid composition was observed in these wines, whereas they exhibited the same biogenic amines composition. The MDG and SDG wines exhibited weaker fruity, floral and caramel aromas compared with the NDG wine. However, these wines showed similar chemical and fatty aromas. Sensory evaluation revealed that these wines could be distinguished by panelists, and the NDG wine was preferred by most tasters, followed by the MDG and SDG wines. These results suggest that the Gouqi wine made from mature berries exhibits the best nutritional and organoleptic quality. However, the over‐matured and severely over‐matured berries could also be useful for Gouqi berry wine production but with different nutritional and sensory properties. Copyright © 2017 The Institute of Brewing & Distilling     

Elevated temperature decouples anthocyanins and sugars in berries of Shiraz and Cabernet Franc

Background and Aim: We tested the hypothesis that elevated temperature decouples anthocyanins and total soluble solids (TSS) in developing berries and explored the effects of fruit load and water supply on the putative decoupling. Methods and Results: We established three 2² factorial experiments where two thermal regimes (elevated temperature, control) where combined with varieties (Shiraz, Cabernet Franc), fruit loads (bunch removal, control) or water regimes (irrigated, water deficit). The relationship between anthocyanins and TSS had a lag phase where TSS increased with no change in anthocyanins and an approximately linear phase where both traits increased in parallel for TSS > 11.4°Brix. Mean residuals in the linear phase were 0.065 mg/g in controls compared with ?0.064 mg/g in the heated treatment, hence demonstrating the thermal decoupling of anthocyanins and TSS across varieties fruit loads and water regimes (P < 0.0001). Delayed onset of anthocyanin accumulation at elevated temperature explained the decoupling. Water deficit increased the anthocyanin : TSS ratio. Conclusion: Elevated temperature decoupled anthocyanins and sugars in berries by a relative shift in onset rather than rate of accumulation of these berry components. Significance of the Study: Warming trends are likely to disrupt the anthocyanin : sugar ratio in berries with consequences for colour : alcohol balance in red wines. Water deficit established shortly before veraison could partially restore these ratios.     

Effect of sulphur dioxide and must extraction on colour,phenolic composition and sensory quality of red table wine

Red wines were made during 1992 from Vitis vinifera var Roriz grapes using a high and a low level of extraction and three levels of total sulphur dioxide (0, 75 and 150 mg SO₂ kg⁻¹). From this single experiment, the effects of total SO₂ and extraction on anthocyanin composition and colour were observed by HPLC, spectrophotometry and tristimulus colorimetry. High extraction produced a wine with more total pigments and total phenols than low extraction and increased the amount of organic acids extracted during fermentation. More anthocyanins were extracted with increasing SO₂ levels. On maturation, all wines lost colour and increased in brownness. Wines made without SO₂ browned more than the wines made with SO₂. The anthocyanins normally present in wines were all rapidly lost to trace levels at 24 months. Vitisin A, a more stable and highly coloured anthocyanin than malvidin 3-glucoside, showed a slower decrease in concentration than malvidin 3-glucoside and contributed significantly to the wine colour during aging. At the first analysis, the wines made without SO₂ had a higher percentage colour due to polymers than the wines made with SO₂. Polymerisation progressed during maturation, although the initial differences were maintained. Sensory analysis after 6 and 18 months storage by expert tasters revealed differences mainly related to the colour attributes, indicating that when wines are made using modern hygienic techniques, total SO₂ has a negligible effect on aroma and flavour attributes. © 1998 Society of Chemical Industry.     

Auxin treatment of pre‐veraison grape (Vitis vinifera L.) berries both delays ripening and increases the synchronicity of sugar accumulation

Background and Aims: Pre‐veraison auxin treatments can delay grape berry ripening, but there is little information about their effects on berry development and wine composition. The aim of this study was to further investigate these effects and explore the practical implications of delaying ripening. Methods and Results: Treatment of pre‐veraison Vitis vinifera L. cv. Shiraz berries with 1‐naphthaleneacetic acid (NAA) significantly delayed ripening as measured by the accumulation of total soluble solids (TSS) and anthocyanins. The onset of the post‐veraison phase of berry size increase was delayed in NAA‐treated fruit, but these fruit were significantly larger than Control fruit at harvest. NAA‐treatments significantly increased the synchronicity of berry sugar accumulation. GC‐MS analysis of wine headspace volatiles showed significant, but largely small, differences in the concentration of 19 compounds. No significant difference in sensory properties was found between replicate small‐scale wine lots made from Control and NAA‐treated fruit. Conclusions: Auxin treatment delayed berry ripening, increased the synchronicity of sugar accumulation between berries, increased berry size and changed the levels of some volatile compounds, but did not affect wine sensory properties. Significance of the Study: We propose that NAA sprays might be used to delay grape berry ripening and increase the synchronicity of sugar accumulation, and therefore ripening, without deleterious effects on wine quality. This may be useful in controlling winery intake and fruit composition.