Terroir 2004 banner
IVES 9 IVES Conference Series 9 Contribution of phenolic compounds to the total antioxidant capacity of Pinotage wine

Contribution of phenolic compounds to the total antioxidant capacity of Pinotage wine

Abstract

The South African wine industry is taking an interest in the enhancement of red wine total antioxidant capacity (TAC) with retention of sensory quality to satisfy the demands of increasingly discerning consumers. The focus is especially on the unique South African red wine cultivar, Pinotage. Pinotage has a unique phenolic composition and commercial Pinotage wines (1998 vintage) has an average TAC of 15.3 mM Trolox equivalents which compares well with that of Cabernet Sauvignon. Knowledge of wine phenolic composition, the antioxidant activity of individual phenolic compounds and their respective contribution to the TAC of wines are needed to evaluate the importance of individual phenolic compounds. The TAC of wines could then be manipulated optimally by using viticultural and enological practices to enhance the content of compounds contributing significantly to the TAC. The aim of the study was to determine the antioxidant activity of individual phenolic compounds in Pinotage wines and their contribution to TAC.
A series of 20 young Pinotage wines were analysed to determine their phenolic composition (reversed-phase HPLC) and TAC (ABTS radical cation scavenging assay). Compounds identified include gallic acid, caftaric acid, caffeic acid, coutaric acid, catechin, procyanidin B1, myricetin-3-glucoside (glc), quercetin-3-glc, kaempferol-3-glc, quercetin-3-rhamnoside, myricetin, quercetin, kaempferol, isorhamnetin, delphinidin-3-glc, peonidin-3-glc, petunidin-3-glc, malvidin-3-glc, delphinidin-3-glc-acetate, vitisinA, petunidin-3-glc-acetate, peonidin-3-glc-acetate, malvidin-3-glc-acetate and malvidin-3-glc-coumarate. The polymeric content of each wine was also estimated as mg catechin equivalents/L. Individual phenolic compounds, available as pure standards (gallic acid, caffeic acid, catechin, procyanidin B1, myricetin-3-glc, quercetin-3-glc, kaempferol-3-glc, quercetin-3-rhamnoside, myricetin, quercetin, kaempferol, isorhamnetin, delphinidin-3-glc, peonidin-3-glc, petunidin-3-glc, malvidin-3-glc), were tested at a range of concentrations and their Trolox equivalent antioxidant capacity (TEAC) values calculated.
Taking the concentration and TEAC values of 24 monomeric phenolic compounds which could be quantified, into account, only 14% of the TAC of the wines could be explained. Possible synergism was ruled out, as the measured and calculated TAC of a mixture of phenolic standards was within the experimental error. Sulphur dioxide additions to the phenolic mixtures at two concentrations had no effect on their TAC. To estimate the contribution of polymeric compounds ultrafiltration was performed in an attempt to separate monomers and polymers in 3 wines. The polymeric compounds, and possibly proteins, isolated using ultrafiltration (50000 dalton nominal molecular weight cut-off), contribute about 30% of their TAC values. A large fraction (59%) of the TAC of a wine is due to unknown compounds which may or may not be phenolic.

DOI:

Publication date: January 12, 2022

Issue: Terroir 2004

Type: Article

Authors

Dalene de Beer (1), Elizabeth Joubert (2), Johann Marais (2), Marena Manley (1)

(1) Department of Food Science, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa
(2) Post-Harvest and Wine Technology, ARC Infruitec-Nietvoorbij, Private Bag X5026, Stellenbosch, 7599, South Africa

Contact the author

Tags

IVES Conference Series | Terroir 2004

Citation

Related articles…

Projected changes in vine phenology of two varieties with different thermal requirements cultivated in La Mancha DO (Spain) under climate change scenarios

The aim of this work was to analyze the phenology variability of Tempranillo and Chardonnay cultivars, related to the climatic characteristics in La Mancha Designation of Origin, and their potential changes under climate change scenarios. Phenological dates referred to budbreak, flowering, veraison and harvest were analyzed for the period 2000-2019. The weather conditions at daily time scale, recorded during the same period, were also evaluated. The thermal requirements to reach each of these phenological stages were calculated and expressed as the GDD accumulated from DOY=60. Changes in phenology were projected by 2050 and 2070 taking into account those values and the projected temperatures and precipitation, simulated under two Representative Concentration Pathway (RCP) scenarios –RCP4.5 and RCP8.5– using an ensemble of models. The average phenological dates during the period under study were, April 16th ± 6.6 days and April 5th ± 6.0 days for budbreak, May 31st ± 6.0 days and May 27th ± 5.3 days for flowering, July 26th ± 5.6 days and July 25th ± 5.8 days for veraison, and Ago 23rd ± 10.8 days and Ago 17th ± 9.0 days for harvest, respectively, for Tempranillo and Chardonnay. The projected changes in temperature imply an average change in the maximum growing season (April-August) temperatures of 1.2 and 1.9°C by 2050, and 1.6 and 2.6°C by 2070, under the RCP4.5 and RCP8.5 scenarios, respectively. A reduction in precipitation is predicted, which vary between 15% for 2050 under RCP4.5 scenario and up to 30% by 2070 under RCP8.5. The advance of the phenological dates for 2050, could be of 6, 7, 7, and 8 days for Tempranillo and 4, 6, 6 and 9 days for Chardonnay, respectively for budbreak, flowering, veraison and harvest under the RCP4.5 scenario. Under the RCP8.5 emission scenario, the advance could be up to 30% higher.

Simulating climate change impact on viticultural systems in historical and emergent vineyards

Global climate change affects regional climates and hold implications for wine growing regions worldwide. Although winegrowers are constantly adapting to internal and external factors, it seems relevant to develop tools, which will allow them to better define actual and future agro-climatic potentials. Within this context, we develop a modelling approach, able to simulate the impact of environmental conditions and constraints on vine behaviour and to highlight potential adaptation strategies according to different climate change scenarios. Our modeling approach, named SEVE (Simulating Environmental impacts on Viticultural Ecosystems), provides a generic modeling framework for simulating grapevine growth and berry ripening under different conditions and constraints (slope, aspect, soil type, climate variability…) as well as production strategies and adaptation rules according to climate change scenarios. Each activity is represented by an autonomous agent able to react and adapt its reaction to the variability of environmental constraints. Using this model, we have recently analyzed the evolution of vineyards’ exposure to climatic risks (frost, pathogen risk, heat wave) and the adaptation strategies potentially implemented by the winegrowers. This approach, implemented for two climate change scenarios, has been initiated in France on traditional (Loire Valley) and emerging (Brittany) vineyards. The objective is to identify the time horizons of adaptations and new opportunities in these two regions. Carried out in collaboration with wine growers, this approach aims to better understand the variability of climate change impacts at local scale in the medium and long term.

Climate, Viticulture, and Wine … my how things have changed!

The planet is warmer than at any time in our recorded past and increasing greenhouse emissions and persistence in the climate system means that continued warming is highly likely. Climate change has already altered the basic framework of growing grapes for wine production worldwide and will likely continue to do so for years to come. The wine sector can continue to play an important role in leading the agricultural sector in addressing climate change. From developing on…

Assessing the climate change vulnerability of European winegrowing regions by combining exposure, sensitivity and adaptive capacity indicators

Winegrowing regions recognized as protected designations of origin (PDOs) are closely tied to well defined geographic locations with a specific set of pedoclimatic attributes and strictly regulated by legal specifications. However, climate change is increasingly threatening these regions by changing local conditions and altering winegrowing processes. The vulnerability to these changes is largely heterogenous across different winegrowing regions because it is determined by individual characteristics of each region, including the capacity to adapt to new climatic conditions and the sensitivity to climate change, which depend not only on natural, but also socioeconomic and legal factors. Accurate vulnerability assessments therefore need to combine information about adaptive capacity and climate change sensitivity with projected exposure to new climatic conditions. However, most existing studies focus on specific impacts neglecting important interactions between the different factors that determine climate change vulnerability. Here, we present the first comprehensive vulnerability assessment of European wine PDOs that spatially combines multiple indicators of adaptive capacity and climate change sensitivity with high-resolution climate projections. We found that the climate change vulnerability of PDO areas largely depends on the complex interactions between physical and socioeconomic factors. Homogenous topographic conditions and a narrow varietal spectrum increase climate change vulnerability, while the skills and education of farmers, together with a good economic situation, decrease their vulnerability. Assessments of climate change consequences therefore need to consider multiple variables as well as their interrelations to provide a comprehensive understanding of the expected impacts of climate change on European PDOs. Our results provide the first vulnerability assessment for European winegrowing regions at high spatiotemporal resolution that includes multiple factors related to climate exposure, sensitivity, and adaptive capacity on the level of single winegrowing regions. They will therefore help to identify hot spots of climate change vulnerability among European PDOs and efficiently direct adaptation strategies.

Elevational range shifts of mountain vineyards: Recent dynamics in response to a warming climate

Increasing temperatures worldwide are expected to cause a change in spatial distribution of plant species along elevational gradients and there are already observable shifts to higher elevations as a consequence of climate change for many species. Not only naturally growing plants, but also agricultural cultivations are subject to the effects of climate change, as the type of cultivation and the economic viability depends largely on the prevailing climatic conditions. A shift to higher elevations therefore represents a viable adaptation strategy to climate change, as higher elevations are characterized by lower temperatures. This is especially important in the case of viticulture because a certain wine-style can only be achieved under very specific climatic conditions. Although there are several studies investigating climatic suitability within winegrowing regions or longitudinal shifts of winegrowing areas, little is known about how fast vineyards move to higher elevations, which may represent a viable strategy for winegrowers to maintain growing conditions and thus wine-style, despite the effects of climate change. We therefore investigated the change in the spatial distribution of vineyards along an elevational gradient over the past 20 years in the mountainous wine-growing region of Alto Adige (Italy). A dataset containing information about location and planting year of more than 26000 vineyard parcels and 30 varieties was used to perform this analysis. Preliminary results suggest that there has been a shift to higher elevations for vineyards in general (from formerly 700m to currently 850 m a.s.l., with extreme sites reaching 1200 m a.s.l.), but also that this development has not been uniform across different varieties and products (i.e. vitis vinifera vs hybrid varieties and still vssparkling wines). This is important for climate change adaptation as well as for rural development. Mountain areas, especially at mid to high elevations, are often characterized by severe land abandonment which can be avoided to some degree if economically viable and sustainable land management strategies are available.