Content uploaded by Anton Pieter Nel
Author content
All content in this area was uploaded by Anton Pieter Nel on Mar 12, 2019
Content may be subject to copyright.
Monopigments (MP), small
polymeric pigments (SPP)
and large polymeric
pigments (LPP) (Part 3)
Keywords: Monopigments (MP), small polymeric pigments
(SPP) and large polymeric pigments (LPP).
Introduction
An encounter with the words monopigments or polymeric pigments
leads one to wonder what they mean exactly. Tannins are divided into
two basic groups, namely the flavonoids and the non-flavonoids. The
non-flavonoids consist of gallic acid, ellagic acid, hydroxycinnamic
acid and hydroxybenzoic acid and their derivatives. Flavonoids
consist of flavonols, flavan-3-ols, flavan-3,4-ols and anthocyanins.
The basic building blocks of tannins and polymeric pigments come
from the two sub-groups, flavan-3-ols and anthocyanins. Flavan-3-ols
consist of (+)-catechins, (-)-epicatechins, (-)-epigallocatechins and
(-)-epicatechin gallate (Fig. 1). There are a few others, but these are not as
important as the four mentioned above. The anthocyanins consist of
five main groups, namely delphinidin, malvidin, peonidin, petunidin
and cyanidin (Fig. 2). Each of these anthocyanins is derivatised with
coumaric acid and acetate.
The different flavan-3-ols usually bind to each other at the C4-C6
and C4-C8 positions to form dimers (Fig. 3). If more flavan-3-ols bind to
each other, trimers, tetramers, oligomers and eventually polymers are
Anton nel1, Pierre vAn rensburg2 &
MArius lAMbrechts2
1 Cape Peninsula University of Technology, Wellington Campus
2 Distell, Stellenbosch
FIGURE 1. Different monomers from which tannins are constructed.
formed (Hanlin et al., 2009). Therefore polymers are long chains of
flavan-3-ols. Anthocyanins also occur freely in the wine at the
beginning of fermentation. These anthocyanins, being very unstable,
are influenced by the pH balance and SO2. At this stage of
winemaking, anthocyanins and other flavonoids stack on top of each
other and this phenomenon is called co-pigmentation (Boulton,
2001). After fermen tation and with maturation, interactions take place
between these flavonoids. Flavan-3-ols react with flavan-3-ols to
form tannins. Flavan-3-ols react with anthocyanins to form other
colour pigments. Anthocyanins may also react with acetaldehydes to
form more stable colour pigments. The more anthocyanins react with
flavan-3-ols, the more stable they become against pH imbalance and
SO2 bleaching.
In a study done by Harbertson et al. (2003) it was found that by
altering the BSA precipitation method with a bisulphite bleaching
process, it is possible to test for monopigments and both small and
large polymeric pigments.
Category: Cellar
Monopigments (MP), small polymeric pigments (SPP) and large polymeric
pigments (LPP) (Part 3)
Anton Nel1, Pierre van Rensburg2& Marius Lambrechts2
1Cape Peninsula University of Technology, Wellington Campus
2Distell, Stellenbosch
Keywords: Monopigments (MP), small polymeric pigments (SPP) and large
polymeric pigments (LPP).
Introduction
An encounter with the words monopigments or polymeric pigments leads one
to wonder what they mean exactly. Tannins are divided into twobasic groups,
namely the flavonoids and the non-flavonoids. The non-flavonoids consist of
gallic acid, ellagic acid, hydroxycinnamic acid and hydroxybenzoic acid and
their derivatives. Flavonoids consist of flavonols, flavan-3-ols, flavan-3,4-ols
and anthocyanins.
FIGURE 1. Different monomers from which tannins are constructed.
The basic building blocks of tannins and polymeric pigmentscome from the two
sub-groups, flavan-3-ols and anthocyanins. Flavan-3-ols consist of (+)-
catechins, (-)-epicatechins, (-)-epigallocatechins and (-)-epicatechin gallate.
There are a few others, but these are not as important as the four mentioned
above. The anthocyanins consist of five main groups, namely delphinidin,
malvidin, peonidin, petunidin and cyanidin (Fig. 2). Each of these anthocyanins
is derivatised with coumaric acid and acetate.
<Insert Figure 2 here (September 2014, page 106)>
FIGURE 2. Different types of anthocyanins.
Compound R1 R2
Cyanidin-3-glucoside OH H
Delphinidin-3-glucoside OH OH
Peonidin-3-glucoside OMe H
Petunidin-3-glucoside OMe OH
Malvidin-3-glucoside OMe OMe
HO
OH
R1
R2
OH
OGlc
FIGURE 2. Different types of anthocyanins.
FIGURE 3. Binding location of flavan-3-ols to form dimers.
Material and methods
The BSA precipitation method described in Harbertson et al. (2003)
was used to determine monomeric anthocyanins (MP), small
polymeric pigments (SPP) and large polymeric pigments (LPP). The
measurements were taken at the following times: After alcoholic
fermentation (AF), after bottling (BOT) and after three months
ageing (3MD). The software STATISTICA (version 10) was used to
analyse the data and compile the graphs.
Five different vinification treatments were used. The treatments are
the following:
•Control (C) – the grapes were crushed, inoculated with WE372
and pressed at the end of fermentation.
•Enzyme treatment (E) – as for the control, except that a pectolytic
preparation was used.
•Cold maceration (CM) – the crushed skins were held at 10°C for
three days before the grapes were inoculated with WE372. After
fermentation the grapes were pressed.
•Post maceration/extended skin contact (PM) – crushed grapes
were inoculated with WE372 and after fermentation the skins
were left on the wine for a further two weeks before being
pressed.
•Combination of cold maceration and post maceration (CM + PM)
– crushed skins were kept at 10°C for three days before the grapes
were inoculated with WE372. After fermentation the skins were
left on the wine for a further two weeks before being pressed.
Tannins were measured using the BSA and MCP methods.
Results
It was to be expected that a large amount of MP would be found after
AF and that the MP would be reduced in due course of time. This is
exactly what happened in the course of this study (Fig. 4), seeing that
the flavan-3-ols and anthocyanins were released from the skins and
grape seeds during the fermentation process. They did not have
sufficient opportunity to polymerise either.
According to Figures 5 and 6 the amount of SPP and LPP after AF
is very little. The amount of SPP and LPP increases from alcoholic
fermentation to bottling. The increase is steeper for SPP than for LPP,
which shows a more gradual increase. A possible reason for this is
the process by which polymers are formed. Monomers first bind to
each other to form dimers, then another binds to form a trimer and
so forth until they form polymers. The more SPP and LPP are formed,
the more stable the colour pigments in the wine will be (Villamor et
al., 2009). Harbertson et al. (2003) also found that more SPP are
formed after AF. Villamor et al. (2009) found that more LPP are
formed in the bottle. This may explain the steeper increase of the LPP
from BOT to 3MD stage and the more gradual increase of SPP over
the same period.
The MP of Cabernet Sauvignon shows that CM, control and PM
treatments all displayed negative effects, while the CM + PM and E
treatments displayed positive effects (Fig. 7). This is not the case with
Shiraz (Fig. 8). Here CM + PM and PM treatments displayed a
negative effect, while the CM, control and E treatments displayed
positive effects. One thing is clear, namely that enzymes have an
enormous influence on the release of flavan-3-ols and anthocyanins
and the corresponding polimerisation thereof. It also looks as though
the success of the various treatments depends on the cultivar being
used. One would expect any treatment that influences the con-
centration of flavonoids, such as the CM and PM treatments, to
display a significant effect on the MP, SPP and LPP amounts. In the
FIGURE 4. Monomeric pigments (MP) of Shiraz from the 2009 harvest season.
STAGE
FIGURE 5. Small polymeric pigments (SPP) formed of Cabernet Sauvignon from the 2009 harvest season.
FIGURE 6. Large polymeric pigments (LPP) formed of Cabernet Sauvignon from the 2009 harvest season.
STAGE
STAGE
FIGURE 7. MP amounts of the various Cabernet Sauvignon treatments crushed in 2009.
FIGURE 8. MP amounts of the various Shiraz treatments crushed in 2009.
TREATMENT
CM + PM treatment, one would expect polymerisation to take place
more rapidly, this being a combination treatment of cold maceration
and extended skin contact. This was indeed the case for Shiraz, but
not for Cabernet Sauvignon.
Conclusion
From this study it transpired that the majority of monomeric
anthocyanins (MP) are formed during alcoholic fermentation and in
turn very few small polymeric pigments (SPP) and large polymeric
pigments (LPP) are present in the wine. As the wine ages, more SPP
and LPP are formed, whereas there is a decrease in MP. Once the
wine is in the bottle, more LPP than SPP are formed, and the colour
pigments become more stable.
Seeing that the enzyme treatment had such a significant effect on
MP, SPP and LPP, one would also like to see what the effect of the
other treatments combined with an enzyme treatment would be. Very
few studies have been conducted on MP, SPP and LPP. There is
hardly any information on the effect of winemaking techniques on
the formation of SPP and LPP, which means that there are plenty of
opportunities for further research. Further research is also necessary
to determine the differences between cultivars with regard to the
formation of MP, SPP and LPP.
Acknowledgement
Winetech for funding the study and Distell for the infrastructure.
Thanks also to the personnel at the Distell experiment cellar and the
respective farms who sacrificed their grapes.
Literature references
Boulton, R., 2001. The copigmentation of anthocyanins and its role in the
color of red wine: A critical review. Am. J. Enol. Vitic. 52(2), 67 - 87.
Hanlin, R.L., Hrmova, M., Harbertson, J.F. & Downey, M.O., 2009. Review:
Condensed tannin and grape cell wall interactions and their impact on tannin
extractability into wine. Austr. J. Grape Wine Res. 1 - 16.
Harbertson, J.F., Picciotto, E.A. & Adams, D.O., 2003. Measurement of
polymeric pigments in grape berry extracts and wines using a protein
precipitation assay combined with bisulfate bleaching. Am. J. Enol. Vitic.
54(4), 301 - 306.
Villamor, R.R., Harbertson, J.F. & Ross, C.F., 2009. Inuence of tannin con
centration, storage temperature and time on chemical and sensory proper ties of
Cabernet Sauvignon and Merlot wines. Am. J. Enol. Vitic. 60(4): 442 - 449.
For further information contact Anton Nel at 021 864 5285 or nelap@cput.ac.za.
Summary
Harbertson et al. (2003) found that when he modified the bovine serum albumen (BSA) assay to include a bisulphite bleaching, he could
determine the monomeric anthocyanins (MP), small polymeric pigments (SPP) and large polymeric pigments (LPP). He also found that
the SPP do not precipitate with a protein, but that the LPP do precipitate with a protein. With this method the evolution of MPP, SPP and
LPP can be followed in fermenting wine and also what happens to the polymeric pigments during maturation. In this study it was found
that there was a large concentration of MP after alcoholic fermentation and this concentration decreased with time. The SPP and LPP
were low in concentration after alcoholic fermentation, but the concentration increased as the wine matured.