2 research outputs found
Properties of Wine Polymeric Pigments Formed from Anthocyanin and Tannins Differing in Size Distribution and Subunit Composition
To
explore the effect of tannin composition on pigment formation,
model ferments of purified 3-<i>O</i>-monoglucoside anthocyanins
(ACN)
were conducted either alone or in the presence of two different tannins.
Tannins were isolated from grape seeds (Sd) or skins (Sk) following
exhaustive extraction in 70% v/v acetone. The Sd and Sk tannin fractions
had a mean degree of polymerization of 5.2 and 25.6, respectively.
The Sd fraction was highly galloylated, at 22%, but galloylation was
<2% in the Sk fraction. The Sk fraction was distinguished by a
high proportion of prodelphinidin, at 58%. After a 6 month aging period,
polymeric pigments were quantified and their color properties determined
following isolation by solid-phase extraction. Wine color and polymeric
pigment were highest in the treatment containing ACN+Sd and similar
in the ACN+Sk and ACN treatments. The same trend between treatments
was observed for total and polymeric nonbleachable pigments. Only
minor changes in tannin subunit composition were found following ACN
incorporation, but the size distribution of polymeric pigments determined
by gel permeation chromatography decreased, in particular for the
ACN+Sk treatment. Color incorporation in the higher molecular mass
range was lower for ACN+Sk wines than for ACN+Sd wines. Compositional
differences between the two tannin fractions may therefore limit the
incorporation of ACNs in the colored form. The results suggest that
in the ACN+Sk and ACN treatments, the formation of lower molecular
mass oligomeric pigments was favored. In polymeric pigments derived
from ACNs, the presence of ethyl- and vinyl-linked ACNs to the level
of trimers was identified using mass spectrometry
Use of Winemaking Supplements To Modify the Composition and Sensory Properties of Shiraz Wine
Wine quality can be significantly
affected by tannin and polysaccharide
composition, which can in turn be influenced by grape maturity and
winemaking practices. This study explored the impact of three commercial
wine additives, a maceration enzyme, an enotannin, and a mannoprotein,
on the composition and sensory properties of red wine, in particular,
in mimicking the mouthfeel associated with wines made from riper grapes.
Shiraz grapes were harvested at 24 and 28 °Brix and the former
vinified with commercial additives introduced either individually
or in combination. Compositional analyses of finished wines included
tannin and polysaccharide concentration, composition and size distribution
by high-performance liquid chromatography, whereas the sensory profiles
of wines were assessed by descriptive analysis. As expected, wines
made from riper grapes were naturally higher in tannin and mannoprotein
than wines made from grapes harvested earlier. Enzyme addition resulted
in a significantly higher concentration and average molecular mass
of wine tannin, which increased wine astringency. Conversely, mannoprotein
addition reduced tannin concentration and astringency. Addition of
enotannin did not meaningfully influence wine composition or sensory
properties