Wine Chemistry and Biochemistry

9A Anthocyanins and Anthocyanin-Derived Compounds 443

structure/organoleptic properties (color and taste) relationship of the corresponding

reaction products is covered in Chapter 4.49D.

vinylflavanols

O

OH

HO

OH +

O

OR

OH

R 1

R 1

R 1

R 1 R^1

R 1

R 1

R 2

R 2

R 1

R 1

R 1

R 2

R 1

R 3 R^4

R 2

R 1

R 2

R 5

R 2

R 1

R 2

R 2

R 2

R 2 R 2

R 2

R 5

R 2

HO

OH

OH

OH

+

O

OR

OH

HO

OH

+O

OR

OH

HO

OH

O

OH

HO

OH

OH

OH

CH 3 -CH CH 3 -CH

O

OR

OH

HO

OH

O

OH

O

OH

OH

OH

O+

OR

OH

HO

O

OH

+

O

OR

OH

HO

OH

O

OR

HO

OH

OH

OH

O+

OR

OH

HO

O

COOH

+O

OR

OH

HO

O

+O

OR

OH

HO

O

OH

Flavanol-anthocyanin

adducts

Anthocyanin-flavanol

adducts

flavanols

Flavanol-ethyl-

anthocyanin adducts

Flavanyl-pyranoanthocyanins

acetaldehyde

VitisinB-pyranoanthocyanins

VitisinA-

pyranoanthocyanins

vinylflavanols vinylphenols

Flavanyl-vinylpyranoanthocyanins

(Portisins)

Hydroxyphenyl-

vinylpyranoanthocyanins

vinylphenolsor pyruvic acid

Hydroxyphenyl-

pyranoanthocyanins

o-quinones of

caftaric acid (CA)

CA-anthocyaninadducts

O

OH

HO

OH

OH

OH

+

O

OR

OH

HO

O

O+

OR

OH

HO

O

OH

HO

OH

OH

OH

O

(c) (b) (d) (e)

+O

OR

OH

HO

OH

OH

OH

HCOC

COOH

COOH

O

HC OH

(a)

(f)

(j) (k)

(i)

(g)

(h)

flavanols,

acetaldehyde

Anthocyanin-ethyl-

anthocyanin dimers

Fig. 9A.3Main chemical reactions of anthocyanins during winemaking

9A.2.1 Reactions of Anthocyanins with Enzymatically Generated

o-Quinones

Precursors.Precursors for this reaction are anthocyanins ando-quinones of caf-

feoyltartaric (caftaric acid) andp-coumaroyltartaric (cutaric acid) acids generated

by enzymatic oxidation by grape polyphenoloxidase (PPO) (Singleton et al. 1985).

PPO first adds an OH group to monophenols and then oxidizes the resultingo-

diphenol too-quinone.

Mechanism of reaction.Under oxidative conditions and for grapes containing

high levels of hydroxycinnamic acids and low of levels of glutathione (a com-

pound that easily reacts witho-quinones, preventing oxidation of phenolic com-

pounds in wines) (Sarni-Manchado et al. 1995), some phenolics are able to react

with theo-quinones of caftaric acid (Cheynier et al. 1986) (see also Chapter 9B).