Thesis (M. Sc.Voedselwet.)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Phenolic compounds in wine, due to their antioxidant activity, are reportedly
responsible for the health-promoting properties of wines. The effect of cultivar
and in-bottle ageing on the antioxidant activity of South African wines in
different types of antioxidant assays was, therefore, investigated.
The antioxidant activity of commercial South African red (Cabernet
Sauvignon, Ruby Cabernet, Pinotage, Shiraz, Merlot) and white (Sauvignon
blanc, Chenin blanc, Chardonnay, Colombard) cultivar wines was compared
using the 2,2’-azino-di-(3-ethylbenzothialozine-sulphonic acid) radical cation
(ABTS·+) scavenging, 2,2-diphenyl-1-picrylhydrazyl radical (DPPH·)
scavenging and microsomal lipid peroxidation (MLP) assays. The red wines
was more effective than the white wines on an “as-is” and an equal total
phenol content. The total antioxidant activity (TAAABTS and TAADPPH) of Ruby
Cabernet was the lowest of the red wines, but the antioxidant potency (APABTS
and APDPPH) of red wine phenolic fractions did not differ (P ³ 0.05). Ruby
Cabernet and Pinotage were the least effective inhibitors of MLP, while Merlot
was the most effective of the red wines. Pinotage phenolic fractions had
lower (P < 0.05) APMLP than that of other red wines. Of the white wines,
Chardonnay and Chenin blanc had the highest and lowest effectivity
respectively according to all antioxidant parameters. Ascorbic acid present in
some wines increased and decreased their TAA and % MLP inhibition
respectively. TAA and % MLP inhibition correlated well (r ³ 0.7, P < 0.001)
with total phenol content of red and white wines, as well as with flavanol
content of red wines and tartaric acid ester content of white wines. The
% MLP inhibition also correlated well with flavanol content of white wines. No
correlation (P > 0.01) was obtained between TAA or % MLP inhibition and
monomeric anthocyanin content of red wines. In the deoxyribose assay, red
wines were more pro-oxidant and exhibited lower hydroxyl radical scavenging
and metal chelating abilities than white wines.
The effect of in-bottle ageing on antioxidant activity of wines was
determined using the ABTS·+ and DPPH· scavenging assays. The TAA and
total phenol content of experimental red (Pinotage and Cabernet Sauvignon)and white (Chardonnay and Chenin blanc) cultivar wines, decreased
(P < 0.05) during 12 months of storage at 0, 15 and 30 ºC. The TAAABTS of
Cabernet Sauvignon and Chardonnay, stored at 30 ºC were lower (P < 0.05)
than at 0 ºC. The APABTS and APDPPH of most wines also decreased during
storage. The monomeric anthocyanin content of red wines decreased
(P < 0.05) rapidly at 15 and 30 ºC. The flavanol content of wines (except
Chenin blanc) increased during the first 9 months, decreasing again after 12
months, while minor changes in the flavonol and tartaric acid ester content of
both red and white wines were observed. The TAAABTS exhibited a good
correlation (r ³ 0.7, P < 0.001) with total phenol content of red and white
wines, as well as with flavonol and tartaric acid ester content of red and white
wines and flavanol content of white wines. The monomeric anthocyanin
content of red wines correlated (r = 0.50, P < 0.001) weakly with TAAABTS.
The decrease in the TAAABTS of wines could thus be mainly attributed to a
decrease in their total phenol content. / AFRIKAANSE OPSOMMING: Die antioksidant aktiwiteit van fenoliese komponente in wyn is waarskynlik
verantwoordelik vir die gesondheidsvoordele daarvan. Die studie het dus
gepoog om effek van kultivar en veroudering na bottelering op die
antioksidant aktiwiteit van Suid-Afrikaanse wyne te ondersoek.
Die antioksidant aktiwiteit van kommersiële Suid-Afrikaanse rooi
(Cabernet Sauvignon, Ruby Cabernet, Pinotage, Shiraz, Merlot) en wit
(Sauvignon blanc, Chenin blanc, Chardonnay, Colombard) kultivarwyne is
vergelyk deur middel van die 2,2’-azino-di-(3-etielbensotialosien-sulfoon
suur)-radikaal katioon (ABTS·+) vernietigingstoets, 2,2-difeniel-1-pikrielhidrasielradikaal
(DPPH·) vernietigingstoets en mikrosomale lipiedperoksidasietoets
(MLP). Die antioksidant aktiwiteit en die antioksidant
kragtigheid (AK) van die rooiwyne was beter as dié van witwyne in al drie
antioksidant toetse. Die totale antioksidant aktiwiteit (TAAABTS en TAADPPH)
van Ruby Cabernet was die laagste van die rooiwyne, terwyl die AKABTS en
AKDPPH van rooiwyn fenoliese fraksies nie van mekaar verskil (P ³ 0.05) het
nie. Van die rooiwyne, het Ruby Cabernet en Pinotage die laagste en Merlot
die hoogste effektiwiteit in die MLP toets getoon. Die AKMLP van Pinotage se
fenoliese fraksies was die laagste van die rooiwyne. Die witwyne,
Chardonnay en Chenin blanc, het onderskeidelik die beste en swakste
antioksidant aktiwiteit en AK van die witwyne getoon in al drie antioksidant
toetse. Askorbiensuur wat in sommige witwyne voorgekom het, het die TAA
van hierdie wyne verhoog, maar hul % MLP inhibisie verlaag. Die TAA en %
MLP inhibisie het goed gekorreleer (r ³ 0.7, P < 0.001) met die totale
fenolinhoud van rooi- en witwyne, asook die flavanolinhoud van rooiwyne en
die wynsteensuur-esterinhoud van witwyne. Die % MLP inhibisie het ook
goed gekorreleer met die flavanolinhoud van witwyne. Geen korrelasie
(P > 0.1) is waargeneem tussen antioksidant aktiwiteit van rooiwyne en hul
monomeriese antosianien-inhoud. Rooiwyn was meer pro-oksidatief in die
deoksieribose toets as witwyne, maar was die swakste hidroksieradikaalvernietigers
en metaalcheleerders.Die effek van veroudering na bottelering op die antioksidant aktiwiteit
van wyne soos bepaal met die ABTS·+ en DPPH· vernietigingstoetse, is
ondersoek. Die TAA en die totale fenolinhoud van eksperimentele rooi-
(Pinotage en Cabernet Sauvignon) en witwyne (Chardonnay en Chenin blanc)
het afgeneem (P < 0.05) tydens opberging na bottelering by 0, 15 en 30 ºC
oor 12 maande. Opberging by 30 ºC het ‘n groter vermindering (P < 0.05) in
die TAAABTS waarde vir Cabernet Sauvignon en Chardonnay veroorsaak as by
0 ºC. Die meeste wyne se APABTS en APDPPH waardes het ook verminder
(P < 0.05) na 12 maande. Drastiese vermindering (P < 0.05) in die
monomeriese antosianieninhoud van rooiwyne is opgemerk tydens opberging
by 15 en 30 ºC. Tydens die eerste 9 maande se opberging het die
flavanolinhoud van wyne toegeneem (P < 0.05) en daarna afgeneem
(P < 0.05) tot by 12 maande, terwyl flavonol- en wynsteensuuresterinhoud van
beide rooi- en witwyne min verandering ondergaan het. Die totale fenolinhoud
van rooi- en witwyne, asook die flavonol en wynsteensuur-esterinhoud van
rooi-en witwyne en die flavanolinhoud van witwyne, het goed gekorreleer
(r ³ 0.7, P < 0.001) met die TAAABTS. In teenstelling met die resultate vir
kommersiële kultivarwyne, was die TAAABTS van rooiwyne swak gekorreleer
(r = 0.5, P < 0.001) met hul monomeriese antosianieninhoud. Die afname in
TAAABTS van wyne tydens veroudering kon dus meestal toegeskryf word aan
die afname in hul totale fenolinhoud.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/16298 |
| Date | 03 1900 |
| Creators | De Beer, Dalene |
| Contributors | Joubert, E., Gelderblom, W.C.A., Manley, M., University of Stellenbosch. Faculty of Agriscience. Dept. of Food Science. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | xv, 237 leaves |
| Rights | University of Stellenbosch |
Page generated in 0.0018 seconds