Improvement of Wine Quality: Tannin and Polymeric Pigment Chemistry

As we were breaking new ground from several perspectives, the project took some unexpected
turns. At this point, we have completed several goals. First, we have created a table of expected
wine pigments based on known reactions between anthocyanins and proanthocyanidins, goals 2a
and 2b. These results were published in two papers, the first describing how to enumerate all
possible proanthocyanidins that could be distinguished by mass spectrometry, up to a degree of
polymerization (DP) of 10 (Cave and Waterhouse 2019), and the second, taking that list and
“reacting” those tannins with the pigment to create a list of all possible wine pigments. This was
a list of over 1 million structures. (Cave et al. 2019)

Having that list, we then compared the masses of those proposed structures with mass spectral
data from two sources, QToF and ICR. In the case of the QToF, we could match about 10% of
the several hundred observable compounds (Cave et al. 2020). However, the ICR is much more
sensitive and precise, and here we could observe about 18,000 signals, and of those could match
over 20% of the signals to entries in our table (Cave et al. 2020). Unfortunately, many signals
could be represented by more than one structure, so additional study is needed to determine
which of the options is present. These results addressed goals 1a, 1b and 2c. The data we now
have will require further mass spectral analysis to discriminate between a number of redundant
structures.