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…

Development of novel drought-tolerant grape cultivars from Monastrell: enhancing anthocyanin and flavonol content under elevated temperatures

The ongoing challenge of climate change is driving the need for novel oenological approaches aimed at finding effective environmental solutions.

Adaptability of grapevines to climate change: characterization of phenology and sugar accumulation of 50 varieties, under hot climate conditions

Climate is the major factor influencing the dynamics of the vegetative cycle and can determine the timing of phenological periods. Knowledge of the phenology of varieties, their chronological duration, and thermal requirements, allows not only for the better management of interventions in the vineyard, but also to predict the varieties’ behaviour in a scenario of climate change, giving the wine producer the possibility of selecting the grape varieties that are best adapted to the climatic conditions of a certain terroir. In 2014, Symington Family Estates, Vinhos, established two grape variety libraries in two different places with distinctive climate conditions (Douro Superior, and Cima Corgo), with the commitment of contributing to a deeper agronomic and oenological understanding of some grape varieties, in hot climate conditions. In these research vineyards are represented local varieties that are important in the regional and national viticulture, but also others that have over time been forgotten — as well as five international reference cultivars. From 2017 to 2021, phenological observations have been made three times a week, following a defined protocol, to determine the average dates of budbreak, flowering and veraison. With the climate data of each location, the thermal requirements of each variety and the chronological duration of each phase have been calculated. During maturation, berry samples have been gathered weekly to study the dynamics of sugar accumulation, between other parameters. The data was analysed applying phenological and sugar accumulation models available in literature. The results obtained show significant differences between the varieties over several parameters, from the chronological duration and thermal requirements to complete the various stages of development, to the differences between the two locations, confirming the influence of the climate on phenology and the stages of maturation, in these specific conditions.

Climate, grapes, and wine: structure and suitability in a variable and changing climate

Climate is a pervasive factor in the success of all agricultural systems, influencing whether a crop is suitable to a given region, largely controlling crop production and quality

Revisiting esters hydrolysis in young white wines

Esters play an essential role in the young white wines’ fruity expression, particularly the groups of ethyl esters of fatty acids (EEFAs) and higher alcohol acetates (HAAs) [1]. However, generally, these groups of esters decrease relatively fast during the first two years of ageing [1, 2].

Alcohol preference and health behaviors in patients with cardiometabolic diseases: insights from the multi-center iact cross-sectional study

Recognizing the influence of alcohol preference on health behaviors is essential for developing tailored interventions that effectively promote healthier lifestyles and optimize disease management strategies in the vulnerable population of patients with cardiometabolic diseases (CMD). The present study aims to provide valuable insights into how alcohol preference relates to dietary habits and medication adherence among patients with CMD diseases.