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SASEV Journal abstracts
The following research results, of which the abstracts are provided here, have been published in the South African Journal of Enology and Viticulture. The full text articles are available on the SASEV website www.sasev.org.
The phenolic composition, total antioxidant capacity (TAC) and colour of Pinotage wines of the 2001, 2002 and 2003 vintages were investigated, using spectrophotometric, high-performance liquid chromatography (HPLC), free radical scavenging and objective colour analyses. Grapes were harvested from grapevines in three climatic regions ranging from cool to warm, with bush (20- and 30-cm trunk height) and trellised (30- and 60-cm trunk heights) vine treatments, on several vineyard sites in each climatic area. Climatic region had a significant effect on the content of several phenolic compounds; the concentration of anthocyanin monoglucosides, flavonols, flavan-3-ols and tartaric acid esters of hydroxycinnamic acids generally increased as the climatic region becomes cooler, while concentrations of acylated derivatives and free hydroxycinnamic acids decreased. Wines made from bush vines contained higher concentrations of flavonols, gallic acid and flavan-3-ols than those from trellised vines, but lower concentrations of some anthocyanin monoglucosides and acylated derivatives, as well as non-coloured polymers. These trends resulted in differences in TAC and objective colour parameters, although the different vintages did not show the same trends in all cases. More vintages should therefore be investigated to clarify these effects. Wines from the cool climatic regions and from bush vines were generally darker coloured, with higher TAC than those from the warm climatic regions and bush vines, respectively. High TAC, therefore, coincided with higher colour quality. Variations in TAC were partly explained by trends for individual phenolic compounds, although unknown compounds played a major role.
South African Journal Enology and Viticulture Volume 27 No. 2 2006 151 - 166
Malic Acid in Wine: Origin, Function and Metabolism during VinificationH. Volschenk1a, H.J.J. van Vuuren2 and M. Viljoen-Bloom1(1) Department of Microbiology, Stellenbosch University, Private Bag X1, 7602 Matieland, South Africa (2) Wine Research Centre, University of British Columbia, Vancouver, B.C. V6T 1Z4, Canada (a) Current address: Department of Food and Agricultural Sciences, Cape Peninsula University of Technology, PO Box 652, 8000 Cape Town, South Africa The production of quality wines requires a judicious balance between the sugar, acid and flavour components of wine. L-Malic and tartaric acids are the most prominent organic acids in wine and play a crucial role in the winemaking process, including the organoleptic quality and the physical, biochemical and microbial stability of wine. Deacidification of grape must and wine is often required for the production of well-balanced wines. Malolactic fermentation induced by the addition of malolactic starter cultures, regarded as the preferred method for naturally reducing wine acidity, efficiently decreases the acidic taste of wine, improves the microbial stability and modifies to some extent the organoleptic character of wine. However, the recurrent phenomenon of delayed or sluggish malolactic fermentation often causes interruption of cellar operations, while the malolactic fermentation is not always compatible with certain styles of wine. Commercial wine yeast strains of Saccharomyces are generally unable to degrade L-malic acid effectively in grape must during alcoholic fermentation, with relatively minor modifications in total acidity during vinification. Functional expression of the malolactic pathway genes, i.e. the malate transporter (mae1) of Schizosaccharomyces pombe and the malolactic enzyme (mleA) from Oenococcus oeni in wine yeasts, has paved the way for the construction of malate-degrading strains of Saccharomyces for commercial winemaking. South African Journal Enology and Viticulture Volume 27 No. 2 2006 123 - 136
Cover Crop Management in a Chardonnay/99 Richter Vineyard in the Coastal Wine Grape Region, South Africa. 1. Effect of Two Management Practices on Selected Grass and Broadleaf SpeciesFourie, J. C.1, Louw, P.J.E.1 and Agenbag, G.A.2(1) ARC Infruitec-Nietvoorbij, Private Bag X5026, 7599 Stellenbosch, Republic of South Africa (2) Department of Agronomy, University of Stellenbosch, 7600 Stellenbosch, Republic of South Africa The trial was conducted over a period of 10 years (1993/94 to 2002/03) on a medium textured soil in a Chardonnay/99 Richter vineyard near Stellenbosch (33°55’S, 18°52’E), situated in the Coastal Wine Grape Region of the Western Cape. Sixteen treatments, consisting of three grain species and five N-fixing broadleaf species managed according to two cover crop management practices, were included. These treatments were compared to a control treatment, in which no cover crop was sown and the weeds were controlled mechanically in the work row and chemically in the vine row from the first week of September to the end of March (grapevine growing season). A treatment in which no cover crop was sown and full surface post-emergence chemical control was applied during the grapevine growing season was also included. The different weed control actions were carried out during the first week of September and/or at the end of November, as well as mid October (1999/00 to 2002/03). Secale cereale L. v. Henog (rye), Avena sativa L. v. Overberg (‘Overberg’ oats), Avena strigosa L. v. Saia (‘Saia’ oats) and Vicia faba L. v. Fiord [only if sown annually and controlled chemically before bud break (BB)], showed the ability to produce, on average, significantly more dry matter during winter than the weeds in the region. The dry matter production of all the cover crops increased from the end of August to the end of November if left to complete their life cycles, with the exception of rye and ‘Overberg’ oats sown in early April. None of the cover crop species were able to reestablish successfully. Continuous effective suppression of winter growing weeds (less than 20% of the weed stand in the control) was achieved with ‘Overberg’ oats (BB) and ‘Saia’ oats (BB), while total suppression was achieved for six and five of the 10 years, respectively. Effective, long-term control of the summer growing weeds was obtainedwith rye (BB), ‘Overberg’ oats (BB) and ‘Saia’ oats (BB). South African Journal Enology and Viticulture Volume 27 No. 2 2006 167 - 177
Long-Term Storage Quality of Table Grapes as Influenced by Pre-Harvest Yeast Applications and Post-Harvest Use of Controlled AtmosphereJeremy A. Klaasen 1,3 Jacobus A. van der Merwe2, Filicity. A. Vries3 and Frederick J. Calitz4(1) South African Herbal Science and Medicine Institute, University of the Western Cape, Private Bag X17, 7535, Bellville, South Africa (2) Post-harvest and Wine Technology Division, Agricultural Research Council (ARC) Infruitec-Nietvoorbij, Private Bag X5026, Stellenbosch, 7599, South Africa (3) Plant Protection Division, Agricultural Research Council (ARC) Infruitec-Nietvoorbij, Private Bag X5026, Stellenbosch, 7599, South Africa (4) ARC Biometry Unit, Private Bag X5026, Stellenbosch, 7599, South Africa The effects of pre-harvest applications of antagonistic yeast and controlled atmosphere storage treatments on inhibiting Botrytis cinerea decay and maintaining the quality of table grapes were compared to identify a treatment that could replace the use of sulphur dioxide (SO2) during post-harvest handling. Treatments for this study included pre-harvest application of antagonistic yeasts Cryptococcus albidus (Yieldplus®), Cryptococcus sp. (LF) and Candida pelliculosa (R951) on table grapes (cvs. ‘Barlinka’, ‘Dauphine’, ‘Red Globe’, ‘Sunred Seedless’ and ‘Thompson Seedless’) from 2001 to 2003. Grapes were stored under regular (air), controlled atmosphere (CA, O2 + CO2) and SO2 conditions at -0.5°C and subsequent storage at a 15°C to simulate shelf-life conditions. Results of this study showed that Botrytis decay levels did not develop rapidly due to low temperatures (-0.5°C vs 15°C), shorter storage periods (4 vs 8 weeks or 0 vs 7 vs 14 days), and CA treatment effects. The CA gas mixtures maintained commercially important low levels (less than 1%) of B. cinerea decay during the cold storage period at -0.5°C. However, during shelf-life storage at 15°C these low levels of decay could only be maintained by some of the SO2 treatments. A necessary commercial requirement is to maintain low decay levels for longer at higher shelf-life temperatures, for which this study cannot conclusively recommend a CA and/or antagonistic yeast treatment as an alternative to SO2. However, pre-harvest applications of the yeast and CA limited the general quality deterioration of the grapes at -0.5°C and 15°C compared to SO2 treatments. Inclusion of macro- or micro-perforated polyethylene packaging liners in combination with CA and pre-harvest yeast treatments did not show obvious negative effects on quality parameters in this study. Discovery and selection of yeast strains that survive under low temperatures and CA conditions would make suitable candidates for continued control of decay development on the fruit surface during shelf-life storage periods. South African Journal Enology and Viticulture Volume 27 No. 2 2006 187 - 195
Water Relations of Vitis vinifera L. cv. Sunred Seedless in Response to Soil Water Depletion Before HarvestP.A. Myburgh and C.L. HowellARC Infruitec-Nietvoorbij, Private Bag X5026, Stellenbosch 7599, South Africa Effects of soil water depletion level and irrigation cut off during ripening on water stress in Sunred Seedless table grapes were studied in a field trial in the Hex River Valley of South Africa. Water status of grapevines subjected to four irrigation treatments was determined prior to harvest during the 2000/01 season. Grapevines of all treatments were irrigated at 40% plant available water (PAW) depletion before véraison. From véraison, i.e. the onset of ripening in December, until harvest at the end of January, two treatments were irrigated at 20% and 40% PAW depletion, respectively. Two more treatments were applied by cutting off irrigation at 20% PAW depletion when total soluble solids reached 12°B and 15°B, respectively. Pre-dawn water stress in grapevines irrigated at 20% PAW depletion until harvest was less than in those where irrigation was cut off at 12°B. Sap flow measurements indicated that partial stomatal closure seemed to have occurred over the warmest part of the day. Apparently, stomatal control limited ?l differences between treatments although extensive soil water depletion occurred where irrigation was cut off during ripening. If accumulated leaf water potential (?T) is considered, irrigation cut off at 12°B and 15°B induced more water stress in grapevines from 04:00 to 24:00 compared to those vines where irrigation was continued until harvest. Where irrigation was continued throughout the ripening period, the level of PAW depletion did not affect ?T. However, during the sunshine period (08:00 until 18:00), ?T in grapevines subjected to 40% PAW depletion, as well as those where irrigation was cut off, was higher than in the ones that were irrigated at 20% depletion until harvest. During the first half of the night, i.e. from 18:00 until 24:00, water potential in grapevines where irrigation was cut off at 12°B was unable to recover to the same level as in those exposed to the other treatments. South African Journal Enology and Viticulture Volume 27 No. 2 2006 196 - 201
Maceration Before and During Fermentation: Effect on Pinotage Wine Phenolic Composition, Total Antioxidant Capacity and Objective Colour ParametersD. de Beer1, E. Joubert 1,2, J. Marais2 and M. Manley1(1) Department of Food Science, Stellenbosch University, Private Bag X1, 7602 Matieland (Stellenbosch), South Africa; DBeerD@arc.agric.za, mman@sun.co.za (2) ARC Infruitec-Nietvoorbij (Fruit, Vine and Wine Institute of the Agricultural Research Council), Private Bag X5026, 7599 Stellenbosch, South Africa; JoubertL@arc.agric.za, MaraisJ@arc.agric.za, VSchalkwykD@arc.agric.za Low-temperature maceration treatments (1, 2 and 4 days at 10 and 15°C) before fermentation and juice/skin mixing treatments (punching-down, pumping-over and rotor action every hour and every 3 hours) during fermentation were investigated in terms of their effects on Pinotage wine phenolic composition, total antioxidant capacity (TAC) and colour over three vintages (2000 to 2002). Results for pre-fermentation maceration were not consistent between vintages. Very few significant differences in the phenolic content, TAC and objective colour parameters were observed between the control wines and wines subjected to different pre-fermentation maceration treatments. Pre-fermentation maceration, especially at 15°C, resulted in wines with increased vitisin A content. Improvement of wine quality when using pre-fermentation maceration treatments at 10°C was noted previously, while no detrimental effect on the wine TAC was observed. The pumping-over treatment yielded wines with lower TAC and phenol content, as well as less favourable objective colour values, indicating that the punching-down or rotor treatment would be preferred. Although mixing at hourly intervals yielded a higher content of some phenolic compounds compared to the 3-hour interval mixing, mixing frequency did not affect the TAC of the wine. The objective colour parameters, h* and b*, were slightly lower at the higher mixing frequency in 2002 indicating a shift in the direction of a magenta hue. South African Journal Enology and Viticulture Volume 27 No. 2 2006 113 - 122
The Biochemistry of Malic Acid Metabolism by Wine Yeasts - A ReviewM. Saayman and M. Viljoen-Bloom1(1) Department of Microbiology, Stellenbosch University, Private Bag X1, 7602 Matieland, South Africa L-Malic acid is an essential intermediate of cell metabolism and the D,L-racemic mixture is used as an acidulant in a variety of foods and beverages. In the wine industry, it plays an important role during grape must fermentation, contributing to the "fixed acidity" that is important. The latter is important in defining the quality of wine. Genetic and biochemical characterisation of the L-malate utilising pathways in several yeast species has indicated that the physiological role and regulation of L-malate metabolism differ significantly between the K(-) and K(+) yeasts. A variety of factors influence the ability of a yeast species to effectively degrade L-malate, including the conditions associated with wine fermentation and the yeast’s intrinsic ability to transport and effectively metabolise L-malate inside the cell. This paper reviews the ability of different yeast species associated with grapes and wine to degrade extracellular L-malate, and the underlying mechanisms in the differential utilisation of L-malate by different yeast species. South African Journal Enology and Viticulture Volume 27 No. 2 2006 113 - 122
Cover Crop Management in a Chardonnay/99 Richter Vineyard in the Coastal Region, South Africa. 2. Effect of Different Cover Crops and Cover Crop Management Practices on Grapevine PerformanceFourie, J. C.1, Louw, P.J.E.1 and Agenbag, G.A.2(1) ARC Infruitec-Nietvoorbij, Private Bag X5026, 7599 Stellenbosch, Republic of South Africa (2) Department of Agronomy, University of Stellenbosch, 7600 Stellenbosch, Republic of South Africa The trial was conducted over a period of 10 years (1993/94 to 2002/03) on a medium textured soil in a Chardonnay/99 Richter vineyard near Stellenbosch (33°55’S, 18°52’E), situated in the Coastal Wine Grape Region of the Western Cape. Sixteen treatments, consisting of three grain species and five legumes, managed according to two cover crop management practices, were included. The one cover crop management practice consisted of cover crops being sown annually and full surface post-emergence chemical control being applied before bud break and when the berries reached pea size (BB). The other management practice consisted of cover crops being sown biennially and postemergence chemical control applied to the vine row before bud break and full surface when the berries reached pea size (AB). From 1999/2000 to 2002/03 the cover crops were sown annually, while the full surface post-emergence chemical control applied at the end of November was advanced to mid-October. These treatments were compared to a control, in which no cover crop was sown and the weeds were controlled mechanically in the work row and chemically in the vine row from bud break to harvest (approximately the first week of February). A treatment in which no cover crop was sown and full surface post-emergence chemical weed control was applied from before bud break to harvest (weedchem) was also included. During the 1994/95 season, the shoot mass of the two-year-old grapevines in the BB treatments was significantly higher than that of the control and the AB treatments. In the following season, the shoot mass and grape yield of the BB treatments was, with the exception of Vicia faba L. v. Fiord (faba bean) and Avena sativa L. v. Overberg, significantly higher than that of the control and weedchem. The grape yield of the control and AB treatments was significantly less than that of weedchem. Although significant differences in shoot mass (2000/01 and 2002/03) and grape yield (2002/03) were detected between treatments, no significant differences could be detected between the BB and AB treatments, with the exception of the shoot mass of Medicago scuttelata v. Kelson (‘Kelson’ medic). The mean petiole NO3-N concentration for the period 1994/95 to 1998/99 tended to be lower in the AB treatment of a cover crop species compared to that of the BB treatment of the same species. In the case of ‘Kelson’ medic (BB) the petiole NO3-N and juice N concentrations were significantly higher than that of the control and weedchem. The juice N concentration of the control and weedchem was significantly less than that of the faba bean treatments during 2000/01 and 2001/02, the Vicia dasycarpa Ten (grazing vetch) and ‘Kelson’ medic treatments during 2000/01, as well as that of Medicago truncatula Gaertn. (BB) and Trifolium subterraneum L. v. Woogenellup (BB) during the 2001/02 season. Wine quality did not differ between treatments. South African Journal Enology and Viticulture Volume 27 No. 2 2006 178 - 186
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