Anthocyanins extraction coefficient

Table 6.14. Variations in the anthocyanin extraction coefficient in wine (a) according to the origin of the grapes (grape varieties, vineyards, vintages) (Glories, 1997, unpublished)...

The potential dissolution of skin pigment varies, especially according to maturity level. Phenolic maturity corresponds to a maximum accumulation of phenolic compounds in the berry. Cellular maturity is defined with respect to the level of cell wall degradation (Volume 2, Sections 6.5.3 6.5.4). Extraction of phenolic compounds increases with this degradation level (Amrani Joutei, 1993). Augustin (1986) defined the anthocyanin extraction coefficient (Ae) as follows ... 

As anthocyanins extracted and/or hydrolyzed from berries are composed of up to 5 different anthocyanidins, the use of one specific anthocyanidin extinction coefficient yields again only an estimate of the content. Differences in extinction coefficients for anthocyanidins present in a sample and biological variations in the anthocyanin distribution influence the test result. 

Quantification of anthocyanins takes advantage of their characteristic behavior in acidic media anthocyanins exist in these media as an equilibrium between the colored oxo-nium ion and the colorless pseudobase form. Using an average extinction coefficient, the total content of anthocyanins may be estimated from the absorption of the total extracts at 520 nm (Moskowitz and Hrazdina 1981). 

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