Ruby Cabernet Research Articles

Temperature Shift Between Vineyards Modulates Berry Phenology and Primary Metabolism in a Varietal Collection of Wine Grapevine.

Global climate change and the expected increase in temperature are altering the relationship between geography and grapevine (V. vinifera) varietal performance, and the implications of which are yet to be fully understood. We investigated berry phenology and biochemistry of 30 cultivars, 20 red and 10 white, across three seasons (2017–2019) in response to a consistent average temperature difference of 1.5°C during the growing season between two experimental sites. The experiments were conducted at Ramat Negev (RN) and Ramon (MR) vineyards, located in the Negev desert, Israel. A significant interaction between vineyard location, season, and variety affected phenology and berry indices. The warmer RN site was generally associated with an advanced phenological course for the white cultivars, which reached harvest up to 2 weeks earlier than at the MR site. The white cultivars also showed stronger correlation between non-consecutive phenological stages than did the red ones. In contrast, harvest time of red cultivars considerably varied according to seasons and sites. Warmer conditions extended fruit developmental phases, causing berry shriveling and cluster collapse in a few cultivars such as Pinot Noir, Ruby Cabernet, and Tempranillo. Analyses of organic acid content suggested differences between red and white cultivars in the content of malate, tartrate, and citrate in response to the temperature difference between sites. However, generally, cultivars at lower temperatures exhibited lower concentrations of pulp organic acids at véraison, but acid degradation until harvest was reduced, compared to the significant pace of acid decline at the warmer site. Sugars showed the greatest differences between sites in both white and red berries at véraison, but differences were seasonal dependent. At harvest, cultivars of both groups exhibited significant variation in hexose/sucrose ratio, and the averages of which varied from 1.6 to 2.9. Hexose/sucrose ratio was significantly higher among the red cultivars at the warmer RN, while this tendency was very slight among white cultivars. White cultivars seem to harbor a considerable degree of resilience due to a combination of earlier and shorter ripening phase, which avoids most of the summer heat. Taken together, our study demonstrates that the extensive genetic capacity of V. vinifera bears significant potential and plasticity to withstand the temperature increase associated with climate change.

Validation of a chromatographic method to routine analysis of trans-resveratrol and quercetin in red wines

Abstract: The objective of this work was to validate a fast method with low-solvent use, for the analysis of trans-resveratrol and quercetin in red wines. The wines were prepared, using a classical method, from the grape (Vitis vinifera) cultivars Cabernet Franc, Cabernet Sauvignon, Malbec, Merlot, Petit Verdot, Pinot Noir, Ruby Cabernet, Syrah, Tannat, and Tempranillo. Samples were filtered and analyzed by high-pressure liquid chromatography (HPLC) with a diode array detector (DAD), at 306 and 371 nm, for trans-resveratrol and quercetin, respectively. An octylsilane column was used, and the mobile phase was composed by a gradient of methanol, water, and formic acid. The method was validated according to the following figures of merit: specificity, linearity, limit of detection, limit of quantification, precision, accuracy, and robustness. The proposed HPLC-DAD method may be established for the analysis of trans-resveratrol and quercetin in red wines.

Malic Acid Distribution and Degradation in Grape Must During Skin Contact: The Influence of Recombinant Malo-Ethanolic Wine Yeast Strains

Wine acidity plays an important role in determining wine quality and ensuring physiochemical and microbiological stability. In high-acid wines, the L-malic acid concentration is usually reduced through bacterial malolactic fermentation, while acidulation in low-acidity wines is usually done during final blending of the wine before bottling. This study showed that skin contact did not influence the relative concentration of L-malic acid in the pulp and juice fractions from Colombard, Ruby Cabernet and Cabernet Sauvignon grape musts, with 32%-44% of the L-malic acid present in the pulp fraction. Four recombinant malo-ethanolic (ME) Saccharomyces wine yeast strains containing the malic enzyme (mae2) and malate transporter (mael) genes of Schizasaccharomyces pombe, effectively degraded the L-malic acid in both the juice and pulp fractions of all three cultivars, with a complete degradation of malic acid in the juice fraction within 2 days.

The Effect of Alternative Pruning Methods on the Viticultural and Oenological Performance of Some Wine Grape Varieties

Three different trials, at three different localities, each with different growing conditions, were conducted with nine different wine grape varieties. Four different pruning methods, hand, mechanical, minimal and no pruning were tested. Growth responses, grape composition and morphology, wine quality as well as labour inputs were evaluated. Huge labour savings were obtained with the alternative pruning methods compared to hand pruning. A reduction in vigour and increase in yield were evident in each variety. Wine quality was not decreased and in some cases even a quality increase was evident. Varieties differ in their adaptability to alternative pruning methods with Cabernet Sauvignon, Pinotage and Chardonnay performing well and Sauvignon blanc and Merlot poorly. Chenin blanc, Shiraz, Colombar and Ruby Cabernet showed acceptable performance. Alternative pruning methods proved to be viable, especially for the production of medium and low priced wines.

Use of Boundary Lines to Determine Effects of Some Salinity-associated Soil Variables on Grapevines in the Breede River Valley

The boundary line concept was used to assess grapevine responses to salinity-associated soil variables. Soil chemical status and grapevine responses were measured in 13 vineyards in the Breede River Valley during the 2001/2002 season. Chardonnay grafted onto 110R and 101-14 Mgt, as well as Ruby Cabernet on the same two rootstocks, was included. The selected vineyards were representative of the variation in salinity-associated soil variables, as well as of leaf and juice element contents previously reported for South African vineyards. Under the prevailing conditions, the four scion-rootstock combinations responded similarly to the salinity-associated variables. The results confirm that soil pH(KCl) should be at least 6.0 for grapevines. The salinity threshold for vineyards in the Breede River Valley should be between 0.7 dS/m and 1.5 dS/m to avoid growth and yield reductions. To reduce the risk of Na toxicity, the SAR should be below 3, and the soluble Na content in the soil should not exceed 5 mg/kg. If gypsum is used to reduce soil Na, it should be applied judiciously to avoid soil SO4 accumulation, thereby reducing the risk of K and Mg deficiencies. Under the prevailing conditions, B and Cl toxicity apparently contributed to reduced vegetative growth. Therefore, soil Cl and B should be kept as low as possible, but care should be taken that B is not reduced to deficient levels. The boundary line concept proved to be useful for determining the effect of a single salinity-associated soil variable on grapevine response.

Fenologia e acúmulo térmico em videiras viníferas na região da Fronteira Oeste do Rio Grande do Sul

Resumo: O objetivo deste trabalho foi avaliar a exigência térmica, obtida por diferentes métodos de cálculo, para caracterizar a fenologia das videiras (Vitis vinifera) 'Cabernet Sauvignon', 'Tannat', 'Ruby Cabernet' e 'Merlot', cultivadas na Fronteira Oeste do Rio Grande do Sul. O desenvolvimento fenológico foi acompanhado durante cinco safras - 2005/2006 a 2009/2010. As temperaturas mínimas e máximas do ar foram coletadas diariamente e foram testados oito métodos de soma térmica: M1.1, M1.2 e M1.3, que utilizaram somente a temperatura base inferior (10°C); M2.1 e M2.2, que consideraram também a temperatura ótima de desenvolvimento de 25°C; e M3.1, M3.2 e M3.3 que, além das anteriores, utilizaram 35°C como temperatura base superior do desenvolvimento. Estes métodos foram comparados pelo erro-padrão das estimativas de soma térmica. O teste SNK foi utilizado para a comparação da exigência térmica entre as cultivares. O método M3.3 foi o que melhor simulou o desenvolvimento em 'Tannat' e 'Merlot' (1.823,1 e 1.780,8 graus-dia respectivamente). No entanto, o menor desvio foi obtido em 'Cabernet Sauvignon' e 'Ruby Cabernet', pelo método M3.1 (1.958,9 e 1.944,8 graus-dia respectivamente). Os métodos que empregaram as três temperaturas cardinais apresentaram maior precisão. 'Tannat' e 'Merlot' são as cultivares de videira que apresentam a menor exigência térmica para completar o ciclo.

Antioxidant comparative effects of two grape pomace Mexican extracts from vineyards on erythrocytes

Maceration and Soxhlet methods were used to obtain methanol extracts from a Mexican grape (Ruby Cabernet) pomace and the biological activity and phenolic profiles were compared. The antioxidant capacity was used to evaluate the mechanism of action, using a physiological model (erythrocytes) of damage induced by AAPH-generated free radicals. The extract obtained by maceration presented a total phenolic content twice the one obtained using the Soxhlet method. It also contained the most potent antioxidants, reducing anisotropy in the presence of AAPH to the levels of untreated cells, restoring membrane fluidity, preventing the morphological changes, as demonstrated by scanning electron microscopy (SEM), and providing protection against protein oxidation at the higher concentration. Our work showed that both extracts presented significant antioxidant activity through positive interactions with the lipid bilayer.

Copigmentation, colour and antioxidant activity of single-cultivar red wines

A hundred and thirty-six single-cultivar red wines of different vintages were collected from several wineries in the Canary Islands in order to study the magnitude of the copigmentation phenomenon and the antioxidant activity. The contribution of free anthocyanins, copigmented anthocyanins and polymeric pigments to the colour of wine, as well as the total phenols, the antioxidant activity (2,2-diphenyl-1-picrylhydrazyl, DPPH method) and the chromatic characteristics of the wines were determined. The influence of ageing time and the climatic conditions on these parameters was also studied. The wines made with Merlot, Ruby Cabernet and Syrah cultivars showed the highest parameters of colour, and the largest contribution to the copigmented anthocyanins was from the Ruby Cabernet, Listan negro and Syrah cultivars. The copigmented anthocyanins and the free anthocyanins decrease with the age of the wine, and the antioxidant activity of the samples appears to be related to the total phenol content. An influence of the climatic conditions on colour parameters has been found. The correlation study between parameters suggests that the parameters b* and L* could be used as suitable indicators of evolution or oxidation stage of red wines.

Discrimination of brazilian red varietal wines according to their sensory descriptors

The purpose of this paper was to establish the sensory characteristics of wines made from old and newly introduced red grape varieties. To attain this objective, 16 Brazilian red varietal wines were evaluated by a sensory panel of enologists who assessed wines according to their aroma and flavor descriptors. A 90 mm unstructured scale was used to quantify the intensity of 26 descriptors, which were analyzed by means of the Principal Component Analysis (PCA). The PCA showed that three important components represented 74.11% of the total variation. PC 1 discriminated Tempranillo, Marselan and Ruby Cabernet wines, with Tempranillo being characterized by its equilibrium, quality, harmony, persistence and body, as well as by, fruity, spicy and oaky characters. The other two varietals were defined by vegetal, oaky and salty characteristics; PC 2 discriminated Pinot Noir, Sangiovese, Cabernet Sauvignon and Arinarnoa, where Pinot Noir was characterized by its floral flavor; PC 3 discriminated only Malbec, which had weak, floral and fruity characteristics. The other varietal wines did not show important discriminating effects.

First Report of Lasiodiplodia crassispora as a Pathogen of Grapevine Trunks in South Africa.

In 2003 and 2004, a survey of grapevine (Vitis vinifera L.) trunk pathogens was conducted in 30 vineyards in the Western and Northern Cape and Limpopo provinces of South Africa. In each vineyard, 20 visually healthy plants were sampled randomly by removing the distal part of one cordon arm. Isolations were made onto potato dextrose agar (PDA) from the internal wood decay symptoms observed in the cordon samples. Seven Botryosphaeriaceae spp. were identified, including Lasiodiplodia crassispora (1). Other Botryosphaeriaceae spp. are known grapevine trunk pathogens (2). Species identity was confirmed by DNA sequence data of the partial translation factor 1-α gene (1) and sequences deposited in GenBank (GU233658 and GU233659). The L. crassispora isolates (CBS 125626 and 125627) were associated with brown internal necrosis, a known symptom of grapevine Botryosphaeriaceae spp. infection (3), in the cordon arms of Ruby Cabernet grapevines occurring in two vineyards in the Northern Cape Province. L. crassispora was described from cankered wood of Santalum album in Western Australia and endophytically from Eucalyptus urophylla in Venezuela (1). Its grapevine pathogen status was determined using both isolates in a repeated pathogenicity test that included three isolates each of Botryosphaeria dothidea and Neofusicoccum australe as positive controls (2), Trichoderma harzianum as a nonpathogen treatment, and an uncolonized agar plug as a negative control. The Botryosphaeriaceae spp. and T. harzianum were plated on PDA and incubated at 25°C for 7 days. Lignified, 6-month-old shoots of grapevine cv. Chardonnay were excised from grapevines with internodes 4 to 6 used for inoculations. Before wounding, shoots were disinfected by submersion for 1 min in a 1 ml/liter solution of a quaternary ammonium compound (Sporekill; ICA International Chemicals (Pty) Ltd, Stellenbosch, South Africa). Twelve shoots were used for each isolate or control treatment. Wounds were made 2 mm deep on the fifth internode of the shoots with a 5-mm flame-sterilized cork borer (2,3). Wounds were inoculated with a pathogen colonized agar plug (5 mm in diameter) or an uncolonized agar plug and then covered with Parafilm (2,3). Inoculated shoots were incubated in the dark in moist chambers for 14 days at 25°C. After incubation, the bark of the shoots was peeled from the area around the wound and the lengths of any resultant lesions were measured under sterile conditions. The inoculum effect was assessed by analysis of variance and Student's t-test. Results showed that significantly (P < 0.0001) longer lesions were caused by L. crassispora (13.36 mm) compared with N. australe (9.27 mm) and B. dothidea (5.28 mm) and also significantly longer than lesions caused by the nonpathogen and negative controls (3.23 and 2.90 mm, respectively). To determine if lesions were caused by inoculated fungi, isolations were made from the tissue at the edges of the lesions by aseptically removing five 0.5 × 1 mm pieces of wood and placing them on PDA dishes amended with 0.04 g/liter of streptomycin sulfate. Dishes were incubated under normal fluorescent light at 25°C for 14 days before identifying isolated fungi based on morphological and cultural characteristics (1). To our knowledge, this is the first report of L. crassispora as a grapevine pathogen.

First Report of Aster Yellows Phytoplasma in Grapevines in South Africa.

For many years phytoplasma diseases have caused serious losses in most of the major grape-growing regions of the world, except South Africa, where a mixed phytoplasma infection was first reported in 2006 (1). During the early growing season of 2006, symptoms consistent with phytoplasma disease were observed in vineyards in the Olifants River Valley. Symptoms included yellowing of leaves, incomplete lignification of shoots, shortening of internodes, and the abortion of growth tips and immature bunches. Symptomatic shoots and leaves from grapevine cultivars (Merlot, Shiraz, Cabernet Sauvignon, Ruby Cabernet, Pinotage, Corinth, Chardonnay, Columbar, Chenin blanc, Sauvignon blanc, Sultana, and Regal) were collected during the early growing season (November) of 2006, 2007, and 2008. Total DNA was extracted from 32 of these samples (from single plants in the same vineyards over the 3 years) with the Invisorb Spin Plant Mini Kit (Invitek, Berlin, Germany) and tested by nested PCR using two universal primer pairs, P1/P7 and R16F2n/R16R2 (3). The first round of PCR of the 2006 samples yielded 1.8-kb fragments for 17 of the samples, while the nested PCR yielded an additional seven positive samples, confirming the necessity of nested PCR for reliable diagnosis. A similar trend was observed in the 2007 and 2008 PCR test results. All asymptomatic plants, which were included as negative controls, and water controls were negative by nested PCR. Twenty-four 1,245-bp amplicons, generated by nested PCR, were excised from gels, purified with a NucleoSpin Extract II Kit (Macherey-Nagel, Düren, Germany) and directly sequenced. Sequence data was compiled with the BioEdit Version 7.0.4.1 sequence alignment editor software (2), aligned using ClustalW Version 1.4 (4), and a consensus sequence was generated (GenBank Accession No. GQ365729). A BLAST search of the NCBI GenBank database using the individual sequences revealed high sequence identities (≥99%) with the aster yellows phytoplasma group (16SrI) and specifically with the subgroup 16SrI-B. In a comparison of the sequences of the 1.2-kb PCR fragments of 24 local samples with each other, sequence identities of ~99% were observed. These results clearly illustrate that all vines screened were infected with the same phytoplasma. Single nucleotide differences observed between different isolates may indicate the presence of closely related sequence variants of this phytoplasma. Aster yellows occurs worldwide and has been reported to infect grapevine-South Africa can now be added to this list. During the three seasons of our study, the area in which symptomatic vineyards were observed increased significantly, indicating spread by a biological vector. Moreover, infected vineyards were noticed in two other South African grape-growing regions. In contrast to the previous report, which reported a mixed infection of phytoplasmas of groups 16SrXII-A and 16SrII-B (1), PCR screening and sequencing of more than 40 individual samples from these areas confirmed these all to be infected with aster yellows phytoplasma only. To our knowledge, this is the first report of the detection and identification of an aster yellows phytoplasma causing grapevine yellows disease in South Africa.

Modelling the relationship between climate, winegrape price and winegrape quality in Australia

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 36:89-98 (2008) - DOI: https://doi.org/10.3354/cr00739 Modelling the relationship between climate, winegrape price and winegrape quality in Australia L. B. Webb1,2,*, P. H. Whetton1, E. W. R. Barlow2 1CSIRO Marine and Atmospheric Research, PMB 1, Aspendale, Victoria 3195, Australia 2School of Agriculture and Food Systems, University of Melbourne, Parkville, Victoria 3010, Australia *Email: leanne.webb@csiro.au ABSTRACT: An essential pre-requisite to exploration of the potential impacts of climate change on wine quality is to establish a robust relationship between winegrape quality and climate. Here, Australian wine industry regional scale climate and winegrape quality information were evaluated. A model that describes the climate sensitivity of quality measures for premium winegrape varieties grown in Australia is presented. The relationship between winegrape quality and climate varies for the different varieties examined: with some varieties, a linear reduction in quality in response to a warmer climate is exhibited, while a quadratic relationship of quality change with increasing temperature is exhibited by some other varieties. For varieties displaying a more linear relationship, the relative sensitivities to changes in growing season temperature can be calculated. For example, Cabernet Franc and Pinot Noir are the varieties displaying the greatest sensitivity to temperature changes in Australian winegrowing regions, while Semillon, Chardonnay and Shiraz are less responsive. For varieties displaying a quadratic relationship of quality to temperature, the optimum growing temperature can be calculated. The optimum mean January temperature (°C) for growing of Cabernet Sauvignon in Australia is 18.5°C; for Shiraz, 19.1°C; Verdelho, 20.7°C; and Ruby Cabernet, 21.5°C. Our study reveals the sensitivity of winegrape quality to climate, and should help to quantitatively inform the Australian wine industry of its potential exposure to projected climatic changes. KEY WORDS: Winegrape price · Winegrape quality · Climate · Temperature · Winegrape variety Full text in pdf format NextCite this article as: Webb LB, Whetton PH, Barlow EWR (2008) Modelling the relationship between climate, winegrape price and winegrape quality in Australia. Clim Res 36:89-98. https://doi.org/10.3354/cr00739 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 36, No. 2. Online publication date: April 30, 2008 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2008 Inter-Research.

Understanding variability in winegrape production systems

Spatial variability in winegrape yield was studied over several vintages in blocks planted to Cabernet Sauvignon, Merlot and Ruby Cabernet in the Coonawarra, Clare Valley and Sunraysia regions of Australia using new yield monitoring technology, a differentially corrected global positioning system (GPS), a geographical information system and some simple methods of spatial analysis. In any given year, yield was highly variable and typically of the order of 10 fold (i.e. 2 to 20 t/ha). However, through the use of k-means clustering and a method based on assessment of the probability of achieving yield targets relative to the mean annual block yield, temporal stability in the patterns of yield variation was demonstrated, even though there were substantial year to year differences in mean annual yield in these blocks. The methods used to demonstrate temporal stability in the patterns of yield variation also promote identification of zones of characteristic performance within variable vineyard blocks. Of significance in this work was the finding that, whilst k-means clustering is the more statistically robust of the two methods used, the ability to incorporate expert knowledge into the yield target method enhances the ability of the manager to accommodate the effects of abnormal events (e.g. an unusually cold flowering period) in the zone identification process. Targeted harvesting of different zones, followed by comparison between commercial lots of wine, provided indication that wine characteristics vary from zone to zone. However, the ranking of wine scores for the various zones changed between seasons. Our results have important implications for the adoption of Precision Viticulture. In particular, they support the introduction of a system of zonal vineyard management. Thus, rather than being managed uniformly, individual blocks can be split into zones in which the management of both inputs to, and outputs from the production system can be applied differentially.

The effect of polysaccharide-degrading wine yeast transformants on the efficiency of wine processing and wine flavour

Commercial polysaccharase preparations are applied to winemaking to improve wine processing and quality. Expression of polysaccharase-encoding genes in Saccharomyces cerevisiae allows for the recombinant strains to degrade polysaccharides that traditional commercial yeast strains cannot. In this study, we constructed recombinant wine yeast strains that were able to degrade the problem-causing grape polysaccharides, glucan and xylan, by separately integrating the Trichoderma reesei XYN2 xylanase gene construct and the Butyrivibrio fibrisolvens END1 glucanase gene cassette into the genome of the commercial wine yeast strain S. cerevisiae VIN13. These genes were also combined in S. cerevisiae VIN13 under the control of different promoters. The strains that were constructed were compared under winemaking conditions with each other and with a recombinant wine yeast strain expressing the endo-beta-1,4-glucanase gene cassette (END1) from B. fibrisolvens and the endo-beta-1,4-xylanase gene cassette (XYN4) from Aspergillus niger, a recombinant strain expressing the pectate lyase gene cassette (PEL5) from Erwinia chrysanthemi and the polygalacturonase-encoding gene cassette (PEH1) from Erwinia carotovora. Wine was made with the recombinant strains using different grape cultivars. Fermentations with the recombinant VIN13 strains resulted in significant increases in free-flow wine when Ruby Cabernet must was fermented. After 6 months of bottle ageing significant differences in colour intensity and colour stability could be detected in Pinot Noir and Ruby Cabernet wines fermented with different recombinant strains. After this period the volatile composition of Muscat d'Alexandria, Ruby Cabernet and Pinot Noir wines fermented with different recombinant strains also showed significant differences. The Pinot Noir wines were also sensorial evaluated and the tasting panel preferred the wines fermented with the recombinant strains.

Understanding variability in winegrape production systems 2. Within vineyard variation in quality over several vintages

Spatial variability in various indices of wine grape quality was studied over several vintages in blocks planted to Cabernet Sauvignon and Ruby Cabernet in the Coonawarra (1999-2002) and Sunraysia (2000-2002) regions of Australia. At both sites, intra-annual variation was marked whilst intra-annual variation was much greater for some indices (e.g. concentration of total phenolics) than others (e.g. Baume). The magnitude of intra-annual variation was readily identified in terms of the 'spread', defined as the difference between the maximum and minimum values, expressed as a % of the median value. Typical values of the spread were 20% for Baume, but could be as high as 117% for phenolics, and better indicated the extent of variation facing the winemaker than the coefficient of variation (CV; typically 3% for Baume and l4% for phenolics). For all attributes, variation in any given year showed marked spatial structure, with the patterns of variation being broadly consistent for each attribute in each year of the study, and with many attributes following similar patterns. The results therefore strongly support the idea of zonal vineyard management. However, fruit quality zone identification is dependent on a large sampling effort. Therefore, given the current availability of yield monitors, the finding that between-zone differences in quality indices were generally significant (P < 0.05) for zones identified on the basis ob yield alone, and, in the absence ob an on-the-go sensing capability, it is suggested that zonal management should proceed on the basis of zones ob characteristic yield productivity. Based on the present work, it is suggested that development ob an on-the-go fruit quality sensing technology would enable the wine industry co maximise its opportunity to gain benefit from differential vineyard management such as selective harvesting. Indeed, the results ob this work suggest that in the absence ob zonal management, preferably supported by on-the-go quality sensing, winemaker demands for delivery of uniform parcels of fruit are unlikely to be satisfied.

Cyanogenic glucosides in grapevine: polymorphism, identification and developmental patterns

Twelve grapevine ( Vitis vinifera L.) cultivars were surveyed for ‘cyanide potential’ (i.e. the total cyanide measured in β-glucosidase-treated crude, boiled tissue extract) in mature leaves. Two related cultivars (Carignan and Ruby Cabernet) had mean cyanide potential (equivalent to 110 mg HCN kg −1 fr. wt) ca. 25-fold greater than that of the other 10 cultivars, and so the trait is polymorphic in the species. In boiled leaf extracts of Carignan and Ruby Cabernet, free cyanide constituted a negligible fraction of the total cyanide potential because β-glucosidase treatment was required to liberate the major cyanide fraction – which is therefore bound in glucosylated cyanogenic compound(s) (or cyanogenic glucosides). In addition, cyanide was liberated from ground leaf tissue of Ruby Cabernet but not Sultana (a cultivar with low cyanide potential). Hence, the high cyanide potential in Ruby Cabernet leaves is coupled with endogenous β-glucosidase(s) activity and this cultivar may be considered ‘cyanogenic’. A method was developed to detect and identify cyanogenic glucosides using liquid chromatography combined with tandem mass spectrometry (LC–MS/MS). Two putative cyanogenic glucosides were found in extracts from leaves of Carignan and Ruby Cabernet and were identified as the epimers prunasin and sambunigrin. Cyanide potential measured at three times over the growing season in young and mature leaves, petioles, tendrils, flowers, berries, seeds and roots of Ruby Cabernet was substantially higher in the leaves compared with all other tissues. This characterisation of cyanogenic glucoside accumulation in grapevine provides a basis for gauging the involvement of the trait in interactions of the species with its pests and pathogens.

Antioxidant activity of South African red and white cultivar wines and selected phenolic compounds: In vitro inhibition of microsomal lipid peroxidation

In vitro inhibition of microsomal lipid peroxidation (MLP) by the major South African red (Cabernet Sauvignon, Ruby Cabernet, Pinotage, Shiraz, Merlot) and white (Sauvignon blanc, Chenin blanc, Chardonnay, Colombard) commercial cultivar wines is presented for the first time. Of the red wines, Merlot was the most effective MLP inhibitor, with Ruby Cabernet and Pinotage being the least effective. Of the white wines, Chenin blanc and Chardonnay were the least and most effective MLP inhibitor, respectively. The mean antioxidant potencies (AP) of the red and white wine total phenols were 14.25 and 4.19, respectively. Ascorbic acid, present in some white wines, counteracted their ability to inhibit MLP. Inhibition of MLP significantly ( P<0.001) correlated with the total phenol content of red ( r=0.90) and white ( r=0.73) wines, as well as the flavanol content ( r=0.88) of red wines and the flavanol ( r=0.79) and tartaric acid ester ( r=0.73) contents of white wines. The MLP inhibitory activities of selected flavonoids were in the order: Quercetin > procyanidin B3 > malvidin > cyanidin ≈ (−)-epicatechin > (+)-catechin ≈ delphinidin.

Antioxidant activity of South African red and white cultivar wines: free radical scavenging.

The free radical scavenging activity of South African red (n = 46) and white (n = 40) cultivar wines was determined using 2,2'-azinobis(3-ethylbenzothialozinesulfonic acid) radical cations (ABTS(.+)) and 2,2-diphenyl-1-picrylhydrazyl radicals (DPPH.). The total antioxidant activities (TAA) of red and white wines using ABTS(.+) were 14.916 and 0.939 mM Trolox, respectively, at corresponding total phenol (TP) contents of 2339.0 and 273.8 mg of gallic acid equiv/L. Ruby Cabernet wines had the lowest TAA(ABTS) (13.177 mM Trolox) of the red wines, whereas the TAA(ABTS) values of Chardonnay and Chenin blanc wines were the highest (1.060 mM Trolox) and lowest (0.800 mM Trolox) of the white wines. The TAA(DPPH) values were of the same magnitude as the TAA(ABTS) values, and similar trends were observed. TAA correlated (P < 0.001) with total phenol content of red (r = 0.935) and white (r = 0.907) wines, as well as flavanol content of red wines (r = 0.866) and tartaric acid ester content of white wines (r = 0.767). Canonical discriminant analysis using phenolic composition and antioxidant activity was applied to differentiate between red and white cultivar wines.

Effect of altitude on the wine-making potential of Listán negro and Ruby Cabernet cultivars in the south of Tenerife island

&lt;p style="text-align: justify;"&gt;In the south of the island of Tenerife (Valle de Güimar), a study was made of the composition of the grape and fundamentally in colour potential during the ripening of the red varieties Listán negro and Ruby Cabernet in two vineyards located at different heights above sea level. The conventional ripening parameters and total and extractable anthocyanin content have been determined in order to estimate all the main characteristic phenolic. Significant differences were detected between the varieties, along with a clear influence of vineyard altitude on accumulation of colour and phenolic substances in the grapes.&lt;/p&gt;

Multivariate differentiation of Spanish red wines according to region and variety

A total of 20 analytical parameters, including alcohols, total polyphenols and anthocyanins, colour and several normal oenological variables such as pH, total acidity and dry extract, were analysed in 66 red wines from two regions of Spain (Aragon and Navarra), made with seven different varieties of grapes (Graciano, Tempranillo, Grenache, Carignan, Merlot, Ruby Cabernet and Cabernet Sauvignon). Factor analysis of raw data provided a good description of the differences between production zones. With the exception of Ruby Cabernet, which presented very outstanding characteristics, grape variety characterisation was more difficult. In this sense, better results were obtained by means of stepwise discriminant analysis. At the end of the discriminant selection process, 94% of the training wines and 85% of the test wines were correctly classified by variety. These percentages were 89% (training sample set) and 92% (test wines) in the classification model obtained from the region. © 2000 Society of Chemical Industry