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Many authors have studied phenolic extraction and how it can be manipulated by winemaking practices.
But most of these studies used small-scale fermentations, which often failed to mimic what actually takes
place at the large scale. In this article, the authors compare the effect of common winemaking procedures
on phenolic composition using commercial-scale fermentations.
· First, let us review the role of the main phenolic compounds. Young red wine color is mainly due to the
concentration of anthocyanins and the degree of copigmentation. In contrast, aged wine color, or stable
color, depends on the formation of polymeric pigments, a product of proanthocyanidins, (also called
condensed tannins or simply tannins) and anthocyanins. Flavanols, another class of phenols, contribute to a
wine’s bitterness and astringency. Flavanol monomers are more bitter than astringent. However, as
flavanol monomers condense, they become more astringent, and less bitter.
· Before summarizing how different winemaking practices affect these compounds, it’s helpful to review
the methodology used to separate them. The authors use two different techniques: normal phase high
pressure liquid chromatography (HPLC), and spectrophotometry. Combining both, they are able first to
separate two fractions: proanthocyanidins and colored proanthocyanidins (the latter absorbing at 520
nm). Then, using HPLC, they further separate proanthocyanidins into 1) low molecular weight
proanthocyanidins (LMWP) and 2) high molecular weight proanthocyanidins (HMWP). They do the same
with colored proanthocyanidins to obtain 3) low molecular weight colored proanthocyanidins (LMWCP)
and 4) high molecular weight colored proanthocyanidins (HMWCP). Finally, using both spectrophotometry
and HPLC, they are able to separate the compounds that contribute to color into three components: 5)
polymeric pigments, 6) copigmented color, and 7) free anthocyanins. Notice the latter three are all color
components, as opposed to “overall color”, “red color”, or simply “color”, which all refer to the more
traditional way of measuring color: the absorbance at 520 nm.

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