EFFECT OF A DEFICIT IRRIGATION REGIME ON THE QUALITY OF WINES MADE FROM WHITE GRAPES (VITIS VINIFERA L.) GROWN IN SEMIARID AREAS

ABSTRACT

The dependence of wine quality on the irrigation management strategies in Vitis vinifera L. was tested from 1999 to 2002. A drip‐irrigation experiment was performed on white grapes of the cultivars Baladí, Airén, Montepila, Muscat Blanc à Petits Grains and Pedro Ximénez, grafted and vineyard‐planted in 1995 in Cabra (Cordoba, Spain). Treatments consisted of a nonirrigated control and an experimental deficit irrigation, in which water was applied from fruit set until near harvest. A total of 19 analytical parameters were measured, including alcohols, total phenol content and optical density as well as ethanol, pH, total acidity and dry extract. Wines were evaluated for their visual characteristics, aroma, taste and finish. The irrigation treatment contributed to a higher dry extract, and an increase in malic acid and potassium in wines. There was a decrease in pH, isobutanol and isoamyl alcohols with increasing water application. Sensory evaluation ranked irrigated over nonirrigated wines with the only exception of the wines of Muscat Blanc à Petits Grains. The main defects of nonirrigated wines were attributed to visual characteristics and poorer taste quality.

PRACTICAL APPLICATIONS

Proper irrigation management, i.e., optimizing both the timing and the amount of water supplied, plays a significant role in wine quality and is especially important in arid and semiarid areas. The aim of this study was to ascertain the effect of irrigation in wine quality. In this study, irrigation was applied only during periods in which water stress might affect production and harvest quality. The chemical results ranked irrigated over nonirrigated wines and Muscat Blanc à Petits Grains over other cultivars, regarding their quality. Sensory evaluation ranked irrigated over nonirrigated wines with the only exception of the wines of Muscat Blanc à Petits Grains. Therefore, deficit irrigation during berry development and ripening appears to be a promising technique for the production of quality young wines in semiarid achieving a compromise between aroma and taste quality.     

Environmental effects on cv Cabernet Sauvignon (Vitis vinifera L.) grown in Hawke's Bay, New Zealand.: 1. Phenology and characterisation of viticultural environments

Six Cabernet Sauvignon vineyard sites in Hawke's Bay (New Zealand), selected out of 28 sites observed in 1996/97, were studied over three consecutive seasons in order to characterise viticultural environments of this region for this cultivar. Indices of precocity of vine phenology were used to analyse the relationship between phenology at the selected sites and vegetative growth, productivity, fruit ripening and wine sensory characteristics. Marked differences in indices of precocity existed between sites. These differences were mostly correlated with vine vegetative growth and canopy indices. There was no relationship between yield and vine phenology. Indices of precocity were correlated with certain juice constituents measured on a common date, as well as the sensory scores of wines produced by microvinification from grapes harvested on different dates and maturity levels. Vineyard sites that differed in indices of precocity also differed in their environmental characteristics, particularly in soil physical properties and water balance.     

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.     

The effect of post-veraison water deficit on yield components and maturation of irrigated Shiraz (Vitis vinifera L.) in the current and following season

Given their perennial nature, grapevines can respond to deficit irrigation during both the current season as well as during the following season, even though full irrigation may have been restored during that second season. To define the cropping responses involved, three post-veraison irrigation treatments were imposed on spur, mechanically and minimally pruned Shiraz vines that were already receiving restricted water application using Partial Rootzone Drying (PRD). The treatments resulted in the vines receiving 1.25 ML per hectare pre veraison and the three irrigation treatments receiving 1.25, 0.65 and 0 ML of water per hectare in the post-veraison period. Water deficit during the current season reduced berry and bunch weight, and yield. Sugar concentration was reduced, and phenolic concentration increased when less water was applied, but anthocyanin concentration was unaffected. Although irrigation was returned to standard practice (PRD) in the following season, yield was reduced in accordance with deficit irrigation treatments the previous season. This reduction in yield was primarily caused by fewer bunches per vine, which in turn was a direct consequence of fewer shoots per vine (lower budburst). The lower crop load on the vines that had received restricted irrigation post-veraison in the previous season resulted in higher sugar and antho-cyanin concentrations in fruit the following season. Lighter pruning resulted in a greater number of smaller bunches comprising smaller berries. In both seasons the minimal pruning treatment delayed fruit maturity as measured by sugar accumulation. Post-veraison water deficit thus has the potential to impact on both yield and fruit composition during the current season as well as during the subsequent season.     

Variation in vine vigour,grape yield and vineyard soils and topography as indicators of variation in the chemical composition of grapes,wine and wine sensory attributes

Background and Aims: Vineyard variability makes satisfaction of winemaker demands for uniform parcels of fruit that are suitable for particular product streams difficult. Indeed, it may not be possible to satisfy these demands without being able to adequately characterise differences between wines derived from different fruit parcels or different areas of the same vineyard, understanding how final wines are affected by management decisions implemented in the vineyard, and/or understanding the effects of variation in the vineyard's biophysical characteristics (e.g. soil, topography) on grape and wine composition. This work sought to identify and examine relationships between the chemical and sensory attributes of wines derived from different parts of the same block and the biophysical characteristics of these different vineyard areas. Methods and Results: Remote sensing of vine vigour, yield mapping and EM38 soil survey were used to identify zones of contrasting vineyard performance in a Cabernet Sauvignon vineyard in the Murray Valley region. Small‐lot wines were made from fruit sourced from these zones. Both sensory and chemical analysis (solid phase microextraction‐gas chromatography‐mass spectrometry) of these wines demonstrated them to be different. Likewise, soil properties and indices of vine nutrition differed between the zones. Conclusions: This work suggests that it is possible for robust relationships to be established between specific (manageable) biophysical attributes of the place where grapes are grown and the sensory and chemical characteristics of the wines derived from them. It also supports the view that terroir is spatially variable at the within‐vineyard scale. Significance of the Study: The work provides a foundation for further research aimed at establishing how specific sensory and/or chemical properties in wines might be modified through targeted management interventions in the vineyard.     

Vine vigour effects on leaf gas exchange and resource utilisation

Background and Aims: Variability in vine vigour is a commonly observed feature in vineyard blocks. Although this aspect is well recognised among viticulturalists, impacts of vigour variability on vine function and resource use efficiency are seldom considered in management decision-making. This study examined influences of vine vigour variability on vine physiological performance and resource use in a commercially managed vineyard block. Methods and Results: The vineyard block was divided into different vigour zones using plant cell density data derived from aerial multi-spectral imaging of the study block. Gas exchange and under-vine soil moisture status were measured in some of the vigour zones. Low vigour vines had consistently lower photosynthesis and stomatal conductance rates than high vigour vines. The differences were evident both during soil-drying and rewetting. Similarly, irrigation water utilisation was markedly lower in low than in high vigour vines. Vine fruit yield was linearly and positively related to vines' capacity to utilise applied water. Conclusions: Vigour has considerable influence on vine physiological performance and on resource utilisation capacity. Uniform irrigation application to a block with variable vigour (which is the norm currently) leads to spatially inefficient resource use, and consequently to a marked within-block variation in irrigation water productivity. Significance of the Study: The demonstration that variation in vigour has a corresponding effect on resource utilisation has direct relevance for managing vineyard inputs such as irrigation or fertilisers.     

Yeast and bacterial modulation of wine aroma and flavour

Wine is a highly complex mixture of compounds which largely define its appearance, aroma, flavour and mouth‐feel properties. The compounds responsible for those attributes have been derived in turn from three major sources, viz. grapes, microbes and, when used, wood (most commonly, oak). The grape‐derived compounds provide varietal distinction in addition to giving wine its basic structure. Thus, the floral monoterpenes largely define Muscat‐related wines and the fruity volatile thiols define Sauvignon‐related wines; the grape acids and tannins, together with alcohol, contribute the palate and mouth‐feel properties. Yeast fermentation of sugars not only produces ethanol and carbon dioxide but a range of minor but sensorially important volatile metabolites which gives wine its vinous character. These volatile metabolites, which comprise esters, higher alcohols, carbonyls, volatile fatty acids and sulfur compounds, are derived from sugar and amino acid metabolism. The malolactic fermentation, when needed, not only provides deacidification, but can enhance the flavour profile. The aroma and flavour profile of wine is the result of an almost infinite number of variations in production, whether in the vineyard or the winery. In addition to the obvious, such as the grapes selected, the winemaker employs a variety of techniques and tools to produce wines with specific flavour profiles. One of these tools is the choice of microorganism to conduct fermentation. During alcoholic fermentation, the wine yeast Saccharomyces cerevisiae brings forth the major changes between grape must and wine: modifying aroma, flavour, mouth‐feel, colour and chemical complexity. The wine bacterium Oenococcus oeni adds its contribution to wines that undergo malolactic fermentation. Thus flavour‐active yeasts and bacterial strains can produce desirable sensory results by helping to extract compounds from the solids in grape must, by modifying grape‐derived molecules and by producing flavour‐active metabolites. This article reviews some of the most important flavour compounds found in wine, and their microbiological origin.     

Developmental variation in sensitivity of Vitis vinifera L. (Shiraz) berries to soil water deficit

A large-scale, long-term irrigation experiment was established near Waikerie in the South Australian Riverland to investigate the feasibility of controlling berry size and ripening at the vineyard scale with modern irrigation systems. Irrigation treatments were devised to impose water stress, by withholding irrigation, during four periods of berry development after flowering of Vitis vinifera (variety Shiraz). Varying water deficits were achieved during each period and between the four seasons, which were climatically diverse. In one season water deficit during the period after flowering resulted in the greatest reduction in berry weight compared with that of well-watered vines, however, in another, water deficit during this period had no effect on berry weight. By comparison, berries appeared to be insensitive to water deficit during the month before harvest in all four seasons. A soil water deficit index was derived to compare the varying levels of water deficit between treatments and seasons on berry development. Deficit effects on berry development were assessed using either comparative growth rate or berry weight near harvest. Regression analysis of berry development against soil water deficit indicated that berries were most sensitive to water stress during the post flowering period.     

Grapevine canopy response to a high‐temperature event during deficit irrigation

Background and Aims: Despite much anecdotal evidence, there has been little scientific investigation of the potential effects of a high‐temperature event on grapevines during deficit irrigation. This study examined the interaction between temperature and water status on leaf physiology. Methods and Results: Two experiments used Cabernet Sauvignon cuttings grown in a glasshouse at approximately 27–30°C before deficit irrigation treatments were imposed. When water stress was apparent, a 2‐day high‐temperature event with maximum daytime temperatures of approximately 40–45°C was generated. Leaf damage, stomatal conductance and water potential of deficit‐irrigated vines were all affected to a greater extent than in the well‐watered vines. Conclusions: The negative effects of a high‐temperature event on vine physiology were more severe in vines experiencing water stress than in well‐watered vines, but recovery was rapid even without re‐watering. Significance of the Study: An increase in the use of deficit irrigation will lead to a greater likelihood of vines being water stressed on hot days, and the observed responses indicate that this will result in greater damage to the vine.     

Shiraz berry size in relation to seed number and implications for juice and wine composition

This study was conducted over three seasons on irrigated Shiraz grapevines growing in a warm climate. We addressed the question of whether differences in berry size (within a population of berries from minimally pruned, own‐rooted or Ramsey‐grafted vines), would lead to differences in juice composition, wine composition or wine sensory score. Predictably, berry mass was found to increase with seed number, but berries in the smallest mass categories (0.3–0.7 g) still had similar juice soluble solids and pH; and similar concentrations of K+, tartaric acid and malic acid, compared with larger berries (1.4–2.0 g). Only for the very smallest mass category (0.3–0.55 g) was there any indication of better colour density (both for own‐rooted and Ramsey‐grafted vines) or higher anthocyanin concentration (for own‐rooted vines) compared with larger berries (1.4–2.0 g). Concentrations of tartaric acid and K+ in berry skins were highest in the smallest berry mass categories (0.3–0.7 g) and decreased with increasing berry mass (up to 1.4–2.0 g). A strong correlation (R²= 0.85) between skin tartaric acid and K+ concentrations was observed across that range. Small‐scale wine lots based on small berries (0.8–0.9 g) versus large berries (1.2–1.3 g) showed no differences in measures such as soluble solids, total acids or pH of juice; nor any differences in pH, total acids, K+, tartrate, malate, spectral characteristics or sensory score of corresponding wines. Moreover, small berries had a similar skin to fruit ratio, and a similar juice yield, compared to large berries. However, when measured post‐fermentation, the ratio of seed weight to skin weight was higher for small berries. The mass range of berries used here for small‐scale winemaking (i.e. from 0.8–0.9 g up to 1.2–1.3 g), covered the range of Shiraz berry mass typically found in irrigated vineyards (from 0.8 to 1.5 g), and thus confirms the relevance of present outcomes to practical winemaking. Finally, our data for variation in juice and wine composition as a function of berry size, showed consistent trends for all seasons, and thus implies that reported instances of improved wine quality from small berries (often associated with certain pruning treatments or deficit irrigation strategies), are more likely due to treatment effects that lead to small fruit, rather than to intrinsic developmental differences between large and small berries.     

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.     

Volatile aroma and sensory analysis of black raspberry wines fermented by different yeast strains

Robus coreanus Miquel is a small berry fruit used for Korean black raspberry (KBR) wine‐making. Twelve different yeast strains were investigated by laboratory‐scale fermentation to develop a wine with a high flavour quality. Volatile aroma compounds from the wines were analysed using headspace–solid phase microextraction–gas chromatography–mass spectrometry and sensory evaluation was performed to evaluate the flavour characteristics. The volatile aroma compounds that mostly contributed to the flavour of KBR wines were those related to fruity (esters) and floral (terpenes) aromas. Fifteen out of the 67 identified volatile compounds showed higher odour activity values than other compounds in the wines, and these compounds were considered as important contributors to the final aromas of the wine. Additionally, the KBR wine fermented by the M1 yeast strain had the highest sensory preference because of higher fruity and floral aroma characters compared with other wines. In addition to the M1 strain, the other yeast strains that produced favourable sensory characteristics included Enoferm CSM, Uvaferm VRB, Lalvin ICV GRE, Lalvin ICV Opale and LevureSeche Active. Of these strains, the M1 strain produced a particularly excellent black raspberry wine, and thus could be applied for further large‐scale production of black raspberry wines. It is also expected that this work will expedite research on the production of high‐quality black raspberry wines with beneficial physicochemical properties, functionality and good sensory characteristics. Copyright © 2015 The Institute of Brewing & Distilling     

Impact of cover crops in vineyard on the aroma compounds of Vitis vinifera L. cv Cabernet Sauvignon wine

This study compared the influence of different cover crops with clean tillage on wine aroma compounds of 5-year-old Cabernet Sauvignon vines. White clover, alfalfa, and tall fescue were used in the vineyard and compared with clean tillage. Aroma compounds of wine were analysed by solid-phase microextraction gas chromatography–mass spectrometry (SPME-GC/MS). Forty-seven volatile compounds were identified and quantified. Wines made from grapes grown with various cover crops had higher levels of aroma compounds. Ethyl acetate, isoamyl acetate, ethyl octanoate, ethyl hexanoate, phenylethyl acetate, isoamyl alcohol, linalool, citronellol, β-damascenone, α-ionone, and 5-amyl-dihydro-2(3H)-furan were the impact odorants of sample wines. Wines from cover crop also had higher contents of these impact odorants than the control. For different cover crops, alfalfa sward yielded the highest levels, followed by the tall fescue treatment. According to the data analysis of aroma compounds and sensory assess, permanent cover crop may have the potential to improve wine quality.     

不同工艺处理对野生猕猴桃酒品质的影响

分别对野生猕猴桃进行清汁、混汁和带皮发酵处理,采用顶空固相微萃取技术对不同酿造工艺野生猕猴桃酒的香气进行富集,用气相色谱-质谱联用技术对其进行定性定量分析,结合酒的基本理化指标和感官评价比较不同工艺处理野生猕猴桃酒的品质。结果表明：混汁发酵和带皮发酵可降低猕猴桃酒的总酸及挥发酸质量浓度,提高pH值,减少VC损失;带皮发酵的香气物质总量显著高于清汁和混汁发酵（P＜0.05）,且酒中的酯类、萜烯类、酮类物质质量浓度相对较高,但酸类物质质量浓度显著降低（P＜0.05）;不同工艺处理酒中特征香气有所差异,其感官香气也各具特色;带皮发酵酒的香气评分较高,猕猴桃品质特征香气突出;且在口感质量、口感浓度、口感纯正度、香气质量、香气浓度、香气纯正度及整体平衡性方面均优于清汁发酵和混汁发酵。因此,带皮发酵工艺可一定程度提高野生猕猴桃酒的品质。     

Phenolic composition and sensory characteristics of Cabernet Sauvignon wines: effect of water stress and harvest date

The effect of three water status level and two harvest date 55 and 64 days after veraison (DAV) on phenolic and sensory composition of Cabernet Sauvignon wines were investigated. The later harvest date led to wine with a higher alcohol content. Total phenols varied from 1439.66 to 1643.08 mg L^?1 with higher values at 64 DAV. No differences were observed between irrigation treatments. For total tannins and anthocyanins, no differences were found between harvest date. Separation of proanthocyanidins by Sep‐Pak Plus tC₁₈ cartridges showed only differences in concentration but not in the proportion of proanthocyanidin fractions. The wines from the most restricted treatment had a better colour and the same aroma of red fruits, persistence, astringency, fullness and bitterness, as the wine from the treatment with highest irrigation. Under the assay conditions, it was possible to obtain wines with a similar chemical and sensory composition earlier and using less irrigation water.