Differentiation among Young and Market-ready Cabernet Sauvignon, Pinotage and Shiraz Wines: Application of Canonical Discriminant Analysis using Flavonoid and Non-Flavonoid Compositional Data

Various factors affect the polyphenol compound concentrations of red grapes. These include cultivar,vineyard location, viticultural practices, microclimate, soil type and winemaking processes. Polyphenolcompound concentrations of young and market-ready Cabernet Sauvignon, Pinotage and Shiraz wineswere examined for the purpose of discrimination between grape cultivars. Thirty-five individual polyphenolcompounds were quantified using a HPLC-DAD method. Stepwise discriminant analysis (SDA) was usedto select a subset of discriminatory variables. In addition, data was grouped and investigated by canonicaldiscriminant analysis, which showed that polyphenol concentrations can be used to discriminate amonggrape cultivars, young wines and market-ready wines. Flavonol, flavanol and anthocyanin patternswere used as a basis for differentiation of young wines, while flavanols and phenolic acids were used fordifferentiation of market-ready wines. Discriminant analysis performed at 95% significance level revealeda 100% categorisation of market-ready and young wines in terms of cultivar and 77.85% categorisation ofa combination of market-ready and young wines in terms of grape cultivar. This illustrates the validity ofpolyphenols for studies pertaining to grape cultivar discrimination

Investigating the Use of Element Analysis for Differentiation between the Geographic Origins of Western Cape Wines

The aim of this study was to differentiate between the geographic origins of wines produced in the Western Cape on the basis of their element composition. A total of 96 market-ready red and white wines (Pinotage, Shiraz, Merlot, Cabernet Sauvignon, Sauvignon blanc, Chardonnay and Chenin blanc) were analysed by means of inductively coupled plasma atomic emission spectrometry (ICP-AES). The discriminant methods: stepwise discriminant analysis, canonical discriminant analysis and linear discriminant analysis were applied to the data sets. A classification accuracy of 38% for Pinotage, 55% for Shiraz, 68% for Merlot, 75% for Cabernet Sauvignon, 93% for Sauvignon blanc, 68% for Chardonnay and 100% for Chenin blanc was achieved. Subject to the conditions of this study, it was concluded that differentiation between wines according to geographical origin was possible using the elemental composition

Phenolic Compounds in Cork-Closed Bottle-Fermented Sparkling Wines

Bottle fermented sparkling wine in South Africa is known as Méthode Cap Classique which is based onthe method used in France for Champagne. The use of cork, instead of a crown cap during the secondfermentation in sparkling wine was investigated for its effect on the phenolic profile of wines. Phenolicacids susceptible to migration from cork into wine were studied in two-disc corks from three differentcommercial suppliers, coded as Cork A, Cork R and Cork C and a crown cap closure. Gallic, caftaric,caffeic and p-coumaric acids were quantified in all samples using a liquid chromatographic technique.Physicochemical parameters were also measured in the wine using a spectrophotometric technique. Totalacidity and pH were not significantly different among the wines. Cork R wines were however significantlydifferent in alcohol. Residual sugar for all samples was below the limit of detection. Gallic acid wassignificantly highest in Cork A wines, which indicates the contribution of Cork A to the concentration ofthis compound in the wine. Different cork types are assumed to release different concentrations of phenoliccompounds. This may be due to differences in surface roughness of cork that would increase the surfacearea in contact with the wine. Therefore, corks from different origins (suppliers) could be used to bringabout subtle differences to the wine. &nbsp

Bottle Fermented Sparkling Wine: Cork or Crown Closures During the Second Fermentation?

Bottle-fermented sparkling wine producers are continuously striving to increase quality and produceniche products. One production tool that could be used is a cork closure instead of a crown cap closureduring the second fermentation and maturation on yeast lees. Anecdotal evidence suggests that thisleads to stylistic differences in the wine. Six pairs of South African bottle-fermented sparkling wines(Méthode Cap Classique), closed by either a cork or crown cap, were investigated. Analyses includedbottle pressure, infrared spectroscopy, phenolic acids, sensory attributes and CO2 kinetics. Generally,there were differences between the cork-closed and crown-capped wines. Cork-closed wines tended tohave lower pressure compared to crown-capped wines, albeit still well within legal requirements. Otherdifferences were evident in the infrared spectral data and in the polyphenol profile of the analysed wines.Levels of gallic, caftaric, caffeic and p-coumaric acids could be used collectively as marker compounds todifferentiate between cork-closed and crown-capped wines. The effect of the cork was also evident in thesensory attributes and CO2 kinetics. Cork-closed wines were judged to have smaller bubbles and a longeraftertaste. It was also shown that the cork-closed wines tended to lose CO2 from the glass slower after beingpoured than their crown-capped counterparts. The data tentatively support the anecdotal evidence thatcork can be used during the second fermentation and maturation on the yeast lees to change the style ofbottle-fermented sparkling wine

Torulaspora delbrueckii Yeast Strains for Small-scale Chenin blanc and Pinotage Vinifications

Nine Torulaspora delbrueckii yeast strains, a commercial T. delbrueckii strain and a commercial Saccharomyces cerevisiae yeast strain were used in the production of small‑scale Chenin blanc and Pinotage vinifications. The fermentations were carried out at 15°C and 24°C respectively. Four T. delbrueckii yeasts were used as single inoculants, while the remainder were inoculated sequentially. The commercial S. cerevisiae yeast strains were added at zero, 24 and 48 hours after the T. delbrueckii strain. The wines were evaluated chemically and sensorially and the data was analysed statistically. The results for the white wine vinification trial showed that two T. delbrueckii treatments could produce novel wines, either on their own or as a component of co‑inoculated fermentations. These compared well with, and even exceeded, the quality of wine produced by the S. cerevisiae reference treatment regarding chemical composition and overall sensory quality. One T. delbrueckii strain showed its robustness by being re-isolated from the yeast lees at the end of fermentation. The red wine vinifications were less conclusive, and no distinctive T. delbrueckii “fingerprint” was observed in the chemical and sensory data, neither was a pattern observed regarding the different inoculation times

Characterisation of Saccharomyces cerevisiae hybrids selected for low volatile acidity formation and the production of aromatic Sauvignon blanc wine

Wine yeasts (Saccharomyces cerevisiae) vary in their ability to develop the full aroma potential of Sauvignon blanc wine due to an inability to release volatile thiols. Subsequently, the use of ‘thiolreleasing’ wine yeasts (TRWY) has increased in popularity. However, anecdotal evidence suggests that some commercially available TRWY intermittently exhibit undesirable characteristics for example, volatile acidity (VA) formation. Therefore, a trial was undertaken to select and evaluate S. cerevisiae hybrids for the production of Sauvignon blanc wine with enhanced fruity and tropical aromas, but low VA. Hybrids were characterised by clamped homogeneous electrical field (CHEF) DNA karyotyping and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) biotyping, and subsequently trialled against top commercial TRWY that is, Zymaflore VL3 and Zymaflore X5 (Laffort Oenologie), and Fermicru 4F9 (DSM Oenology) in laboratory-scale Sauvignon blanc vinifications during 2013. Most hybrids produced wines with VA levels significantly lower than those produced with Zymaflore VL3, Zymaflore X5 and Fermicru 4F9. Low VA forming hybrids also produced wines with tropical wine aroma notes. Wines produced by Fermicru 4F9 had the lowest acetic acid (the main volatile acid) of the commercial TRWY in this study. However, some hybrid yeasts produced wines with less acetic acid on average than wines produced by Fermicru 4F9. Overall, hybrids NH 6, NH 48, NH 56, NH 88 and NH 145 produced wines with enhanced tropical fruity aroma, but lower VA compared to wines produced by commercial TRWY.Keywords: Hybrid yeasts, CHEF, MALDI-TOF/TOF MS biotyping, Sauvignon blanc, tropical fruit aroma, volatile acidit

Effect of Cover Crops, and the Management Thereof, on the Weed Spectrum in a Drip-irrigated Vineyard: 1. Weeds Growing During Winter and From Grapevine Bud Break to Grapevine Berry Set

A five-year trial (2009 to 2013) was executed in a drip-irrigated full-bearing seven-year-old Shiraz/101-14 Mgt vineyard established on a sandy to sandy clay loam soil at Blaauwklippen Farm (33°58’S, 18°50’E) near Stellenbosch, South Africa. Fourteen treatments, consisting of two management practices applied to five cover crop species, as well as winter-growing weeds (no cover crop) and winter-growing weeds (no cover crop) with nematicide applied in the vine row, were applied. The effect of the five cover crop species, either controlled chemically (CC) or mechanically (MC) during grapevine bud break, on the weed spectrum was determined at the end of winter and during grapevine berry set. Total suppression of Loliumspecies (ryegrass) was achieved with Avena sativa cv. Pallinup (oats) (CC) and Eruca sativa cv. Nemat (Nemat) (CC) after three years. A grass-specific herbicide applied at the end of May 2012 terminated the dominance of ryegrass and facilitated the dominance of Erodium moschatum (musk heron’s bill). Sowing the cover crops as late as 2013-05-23 prevented ryegrass from regaining its dominance. After five winters, ryegrass was totally eradicated from oats (CC), oats (MC), Sinapus alba cv. Braco (white mustard) (CC) and Nemat (CC). Musk heron’s bill was totally suppressed in all treatments during berry set within two seasons and ryegrass in all the CC treatments by 2011. This probably facilitated the dominance of Digitaria sanguinalis (crab fingergrass).

Effect of Cover Crops, and the Management Thereof, on the Weed Spectrum in a Drip-irrigated Vineyard: 2. Weeds Growing From Grapevine Berry Set to Post-harvest

A five-year trial (2009 to 2013) was executed in a drip-irrigated seven-year-old Shiraz/101-14 Mgt vineyard established on a sandy to sandy clay loam soil at Blaauwklippen Farm (33°58’S, 18°50’E) near Stellenbosch, South Africa. Fourteen treatments, consisting of two management practices applied to five cover crop species, as well as winter-growing weeds (no cover crop) and winter-growing weeds (no cover crop) with nematicide applied in the vine row, were applied. The weeds and cover crop species were eithercontrolled chemically (CC) or mechanically (MC) during grapevine bud break, followed by full-surface chemical control during berry set (for both CC and MC treatments). Rhynchelytrum repens (Natal redtop)dominated the post-harvest pre-treatment weed spectrum in all the treatments except Eruca sativa cv. Nemat (Nemat) (MC). This species lost its post-harvest dominance from 2010 onwards. It seems that the relatively low summer rainfall during the 2010/2011 season allowed Anagallis arvensis to appear in April 2011 and dominate some of the treatments, which coincided with the disappearance of Cynodon dactylon (common couch) and Polygonum aviculare (prostrate knotweed). Digitaria sanguinalis, common couch and prostrate knotweed seemed to establish better during late summer where MC was applied. The pre-treatment average post-harvest weed stand of 5.53 t/ha was reduced to 0.53 t/ha within one season, illustrating the benefit of full-surface chemical weed control applied during grapevine berry set

Integrative Effects of Vine Water Relations and Grape Ripeness Level of Vitis vinifera L. cv. Shiraz/Richter 99. II. Grape Composition and Wine Quality

Regulation of grapevine water status is a common practice to manipulate grape composition and winequality. In this investigation the effect of plant water status (two field water capacity-based irrigation levels,75% and 100%, applied at single and combined vine developmental stages) and ripeness level (harvestingat different soluble solid levels) on grape composition and wine quality of Vitis vinifera L. cv. Shiraz/Richter 99 was determined. Integrative effects of vine water relations and grape ripeness level, specificallyin a Mediterranean high winter rainfall area, have not yet been investigated systematically. Source:sinkmechanisms and dynamics and compositional and physical changes during both green berry and ripeningperiods (and in response to environment changes), seemed critical for the final grape composition and winequality/style. Despite relatively favourable conditions of the experiment terroir, additional water was stillrequired to obtain best grape and wine quality. Skin colour and total phenolic contents were stimulated inparticular by 75% (field water capacity) pea size (PS) irrigation, post-véraison (PV) irrigation and 75% peasize+post-véraison irrigation, until the last harvest stage. Treatments that included post-véraison irrigationwere not negative in terms of ripening parameters. Increasing total soluble solids with ripening were notfollowed in parallel by anthocyanin potential. Anthocyanin extractability increased with ripening. A late,overripe harvest may result in wines that are slightly better coloured, but highly alcoholic and tannic.Furthermore, at high ripeness level, differences between treatments largely diminished. Over-ripenessof grapes may have tempering and even negative effects on expected outcomes of seasonal cultivationefforts to produce unique wines. This would not favour economic viability. Although non-irrigated winesfailed to result in exceptional wine quality at any harvest stage, a better result in overall quality wasobtained in comparison to irrigation treatments applied at all stages. Berry and wine composition resultscorresponded with findings on wine sensorial quality. The 75% PS, PV irrigation, and 75% PS+PVirrigation consistently resulted in good quality wines. At the first harvest stage, 75% PV, 100% PV, 75%PS+V and 75% PS+PV irrigations gave most prominent wines; at the second harvest stage, vines irrigated75% at PS, 75% at PS+PV and 75% at PV delivered most prominent wines; and at the third harveststage, 75% PV, 100% PV, 75% PS and 75% PS+PV resulted in most prominent wines. These treatmentsrepresented different wine styles at each harvest stage. Restricted PS irrigation and PV irrigation, as singleor combined treatments, featured prominently in favouring grape and wine composition and wine sensorialquality. Physical and compositional changes in ripening berries and the impact on wine quality and stylewere further clarified. New perspectives on managing time of harvesting with varying vine water status aregiven. Recommendations on vine water status management strategies required to obtain different grapecomposition and wine style are made

A comparison of experimental designs for cultivar evaluations

CITATION: Saul, H., Booyse, M. & Swanepoel, P. A. 2020. A comparison of experimental designs for cultivar evaluations. South African Journal of Plant and Soil, 37(2):144-151, doi:10.1080/02571862.2019.1703049.The original publication is available at https://www.tandfonline.comSpatial heterogeneity and the lack of clear or significant treatment responses in agricultural field experiments complicates recommending the most suitable cultivar(s) to producers for a specific area. Increased attention should be given to the experimental design of cultivar trials, as failure to capture spatial heterogeneity may increase the unexplained variance and thus might influence the accuracy of results. A randomised complete block design (RCBD) is the most popular design in variety trials in South Africa. However, latinised row-column designs (LRCD) is widely recommended in literature for field experimentation, because of the efficiency to control heterogeneity in two dimensions. The aim of this study was to compare the efficiency of RBCD with LRCD and recommend the more appropriate design for use by practitioners in cultivar trials. Wheat (Triticum aestivum) was used as a test crop. An analysis of variance was performed on the data produced from both designs conducted on wheat in the Swartland region of South Africa over a two-year period. An LRCD provided better accuracy and model or design estimations than RCBD. The results demonstrated the value of eliminating variance in two directions rather than one direction. We therefore recommend the use of LRCD in preference to RCBD in variety trials.https://www.tandfonline.com/doi/abs/10.1080/02571862.2019.1703049Post-prin