Anthocyanins and their variation in red wines. II. Anthocyanin derived pigments and their color evolution

Abstract

Originating in the grapes, anthocyanins and their derivatives are the crucial pigments responsible for the red wine color. During wine maturation and aging, the concentration of monomeric anthocyanins declines constantly, while numerous more complex and stable anthocyanin derived pigments are formed, mainly including pyranoanthocyanins, polymeric anthocyanins produced from condensation between anthocyanin and/or flavan-3-ols directly or mediated by aldehydes. Correspondingly, their structural modifications result in a characteristic variation of color, from purple-red color in young red wines to brick-red hue of the aged. Because of the extreme complexity of chemical compounds involved, many investigations have been made using model solutions of know composition rather than wine. Thus, there is a large amount of research still required to obtain an overall perspective of the anthocyanin composition and its change with time in red wines. Future findings may well greatly revise our current interpretation of the color in red wines. This paper summarizes the most recent advances in the studies of the anthocyanins derived pigments in red wines, as well as their color evolution.

Figure 1

General structures of pyranoanthocyanins derived from anthocyanidin-3-O-glucoside in red wines and the dynamic equilibrium between their different flavylium cation forms. The R₁ and R₂ groups could be H, OH, OCH₃. The R₃ groups could be H, COOH, CH₃, (vinyl)phenols, (vinyl)flavanols [47,48].

Figure 2

The structures of vitisin A and vitisin B generated from malvidin-3-O-glucoside [47,70,71].

Scheme 1

Formation mechanism of vitisin A [47,48,74].

Figure 3

The structures of hydroxyphenyl-pyranoanthocyanins generated from malvidin-3-O-glucoside [24,61,82].

Scheme 2

Formation mechanism of Pinotin A [51,87].

Figure 4

The structures of flavanyl-pyranoanthocyanins generated from malvidin-3-O-glucoside and 8-vinylcatechin or 8-vinylprocyanidin [47,92].

Scheme 3

Formation mechanism of flavanyl-pyranoanthocyanins [47,92].

Scheme 4

Formation mechanism of flavanyl/phenyl-vinylpyranoanthocyanin derived from carboxy-pyranoanthocyanins: (a) A type portisins (flavanyl-vinylpyranoanthocyanin); (b) B type portisins (phenyl-vinylpyranoanthocyanin) [96,103].

Scheme 5

Formation mechanism of oxovitisins (pyranone-anthocyanin) derived from carboxy-pyranoanthocyanins [104].

Scheme 6

Proposed two pathways for the formation of pyranoanthocyanin dimers [47,106].

Scheme 7

Formation mechanism of ‘anthocyanoellagitannin’ pigment derived from malvidin-3-O-glucoside and (−)-vescalagin [109].

Scheme 8

The equilibria among the different structural forms of T-A or A-T type anthocyanin/tannin adducts in aged red wines [113].

Scheme 9

Proposed mechanism of T-A and A-T adducts formation [112,118,119,120,123].

Figure 5

Structures of some directly condensed oligomeric anthocyanins [133,134,135].

Figure 6

Structures of some mediated condensed oligomeric anthocyanins [91,139,140,141,142].

Scheme 10

Proposed mechanism of acetaldehyde mediated tannin–anthocyanin additions [32,144,145].

Figure 7

Structures of some xanthylium pigments [159,160,161,162].

Scheme 11

Evolution of anthocyanins in aged red wines [14,24,57].