Effects of mechanical thinning on fruit and wine composition and sensory attributes of Grenache and Tempranillo varieties (Vitis vinifera L.)

Background and Aims: Cost-effective yield control is required by the wine industry in order to reduce the existing worldwide wine surplus and to improve grape quality. The object of this study was to evaluate the chemical and sensory effects on the resulting wines of mechanical cluster thinning performed at different intensities on Grenache, and at different timings (pea size and veraison) on Tempranillo. Methods and Results: The experiments were conducted with a machine harvester in 2007 on two commercial vertical shoot-positioned vineyards in Spain's Rioja region. In both varieties, mechanical thinning was effective in yield reduction and resulted in more ripened fruit, and wines with higher alcohol and pH values, more intense colour and increased phenolic content. Regardless of the thinning intensity, sensory changes were less noticeable in Grenache than in Tempranillo wines. Of the latter, those from vines thinned during veraison were less aromatic and sour, but had increased astringency. Conclusions: Yield management through mechanical thinning induced changes to the chemical composition of fruit and wines as well as to the wines' aroma, taste and mouthfeel. The extent of the sensory implications seems to depend on several factors such as the variety and timing of thinning application. Significance of the Study: This is one of the first studies addressing the effects of mechanical thinning on the sensory properties of the resulting wine and has implications for viticultural management practices.     

浸渍酶对蛇龙珠葡萄酒酿造过程中类黄酮化合物变化的影响

研究了浸渍酶Lallzyme Ex-V对蛇龙珠葡萄酒酿造过程中(从酒精发酵到橡木桶贮藏12个月)类黄酮动态变化的影响。结果显示,经浸渍酶处理加快了儿茶素、表儿茶素、杨梅素、山奈酚和槲皮素等5种类黄酮化合物在葡萄酒酒精发酵期间的浸提速度,但不影响杨梅素和槲皮素在后续酿造过程中的含量,杨梅素在葡萄酒酒精发酵结束后含量逐步下降,槲皮素在橡木桶陈酿期间含量逐渐增加;酶处理对儿茶素和表儿茶素的影响一直持续到苹-乳发酵的第2周,酶处理酒中儿茶素和表儿茶素的含量高于对照;浸渍酶对山奈酚含量的影响一直持续到橡木桶陈酿3个月,处理酒中的含量高于对照。     

Effect of vine age on vine performance of Shiraz in the Barossa Valley,Australia

Background and Aims

Old vineyards are often suggested to be superior to younger ones, a claim that has scarcely been investigated scientifically. The aim of this study was to investigate if vineyard age influences vine performance.

Methods and Results

Five commercial Shiraz vineyards in the Barossa Valley, SA, were selected; each site contained younger vines, which had been vegetatively propagated from older vines on the same site. Measurements of vegetative growth and reproductive development were obtained over three seasons. Results show that the effect of vine age is difficult to measure and separate from seasonal and site interactions. Vine age was strongly correlated with trunk circumference. Vines aged 49 years showed more similarities with older vines (93–168 years old) than with younger vines (6–28 years old).

Conclusions

Vine age had an impact on grapevine reproductive performance. Older vines produced a yield greater than that of younger vines. Greater vine size, measured by increase in trunk circumference over time, may be a key determining factor in increased reproductive capacity.

Significance of the Study

Vine age is commonly attributed to superior vine performance, as a precursor to fruit and wine quality. Our findings suggest that increasing vine age had a positive effect on reproductive performance in terms of yield, contrary to popular belief. This establishes a starting point for future studies that are underway to quantify if these findings have an effect on fruit and wine composition and sensory attributes.     

Suitability of pre‐dawn and stem water potential as indicators of vineyard water status in cv. Tempranillo

Background and Aims: Irrigation management requires the collection of up‐to‐date information that allow growers to make rapid decisions, water potential being one of the most used parameters in irrigation scheduling. The goal of this research was to determine whether predawn (Ψpd) and stem (Ψs) water potential can be used equally well, quantifying the effect external factors have on the relationship between them. Methods and Results: Ψpd, mid‐morning (Ψs‐m) and noon (Ψs‐n) stem water potential were measured at seven cv. Tempranillo vineyards. Climatic conditions, vine growth and fruit load affected daily water potential dynamics. A greater decline of Ψs occurred when temperatures were higher and there was no dew formation, as well as under larger canopies and fruit load. While the relative impact of these variables on water potential was not particularly high, it was by no means negligible. Conclusions: Data collected in this study did not favour Ψpd, Ψs‐m or Ψs‐n as a preferred measure to evaluate plant water status. It is important to remark that similar Ψpd values do not necessarily indicate the same level of deficit, and that similar Ψs values do not always mean similar water availability. Therefore, a straightforward interpretation of Ψpd and Ψs can sometimes be misleading. Significance of the Study: The results obtained provide significant explanation to the lack of agreement in the literature regarding the most suitable time to measure water potential. Vineyard managers and scientists should select it according to the level of stress expected, climatic conditions and irrigation frequency.     

Exclusion of sunlight from Shiraz grapes alters wine colour, tannin and sensory properties

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.     

Berry size and vine water deficits as factors in winegrape composition: Anthocyanins and tannins

Soluble solids, seed tannin, skin tannin, and skin anthocyanin were measured in fruit from Cabernet Sauvignon vines that had experienced either High, Control or Low water status during ripening. Berries from each treatment were segregated into 6 size categories at harvest in order to test independently for relationships due to size compared with those due to water deficits. Berry content of all solutes increased approximately in proportion to the increase in berry size. Deviations from proportionality caused Brix and anthocyanin concentration (mg per unit berry fresh mass) to decrease, and the concentration of skin tannin to remain unchanged or decrease slightly with increasing berry size. The concentration of seed tannin did not decrease and appeared to increase with berry size in multiple-seeded berries. In comparison with skin tannin or anthocyanin content, seed tannin content varied more with berry size and less with vine water status. In addition to decreasing berry size, water deficits increased the amount of skin tannin and anthocyanin per berry and the concentrations of skin tannin and anthocyanins, but did not significantly affect the content or concentration of seed tannin. The results show that there are effects of vine water status on fruit composition that arise independently of the resultant differences in fruit size. The effect of vine water status on the concentration of skin tannin and anthocyanin was greater than the effect of fruit size on those same variables. However, the increases in skin tannin and anthocyanin that accompanied water deficits appear to result more from differential growth sensitivity of inner mesocarp and exocarp than direct effects on phenolic biosynthesis.     

Methoxypyrazine Analysis and Influence of Viticultural and Enological Procedures on their Levels in Grapes,Musts, and Wines

This review discusses the factors that affect the concentrations of methoxypyrazines (MPs) and the techniques used to analyze MPs in grapes, musts, and wines. MPs are commonly studied pyrazines in food science due to their contribution of aroma and flavor to numerous vegetables such as peas and asparagus. They are described as highly odorous compounds with a very low olfactory threshold. The grape varietals that exhibit green or herbaceous aromas that are characteristic of MPs are predominantly Vitis vinifera cv. Cabernet Sauvignon and Sauvignon Blanc, but include others. The most extensively studied MPs include 3-isobutyl-2-methoxypyrazine, 3-isopropyl-2-methoxypyrazine, and 3-sec-butyl-2-methoxypyrazine. It outlines the significance of methoxypyrazines in grapes, musts, and wines in terms of the concentrations that are capable of contributing their sensory characteristics to wines. This review discusses methods for analyzing MPs including gas chromatography-mass spectroscopy (one or two dimension) and high-performance liquid chromatography, the appropriate extraction techniques, and the efficacy of these methods. Additionally, this review explores factors that affect pyrazine content of grapes, must, and wines, such as the effects of different viticultural practices, effects of light exposure and grape maturation, climate, soil, the multi-colored Asian lady beetle and the effects of different vinification processes.     

Volatile composition and aromatic attributes of wine made with Vitisvinifera L.cv Cabernet Sauvignon grapes in the Xinjiang region of China: effect of different commercial yeasts

The Xinjiang region is a major grape- and wine-production area in China, but the region’s notably high temperatures in the summer and year-round intense sun exposure play negative roles in the aroma, complexity, and elegance of Cabernet Sauvignon wine. In this study, Cabernet Sauvignon grapes harvested in this region were fermented on an industrial scale using four commercial yeast strains (L2323, D254, RVA, and CECA) and spontaneous yeast (NF). The results showed that a total of 123 volatile compounds were detected and 15 volatile compounds significantly contributed their flavor notes to the wine’s overall aroma. The use of RVA and CECA strains resulted in wine with higher concentrations of higher alcohols, terpenes and norisoprenoids. However, the D254-fermented wine showed high level of esters and carbonyl compounds. Wine fermented with the L2323 and D254 strain possessed a stronger fruity aroma, whereas the RVA strain enhanced the herbaceous, chemical, and fatty aromas in wine. Principal component analysis revealed that a significant aromatic feature difference was observed in these wines after alcoholic and malolactic fermentation. The use of different commercial yeast strains altered the aromatic profile of Cabernet Sauvignon wine.