A New Insight into the Degradation of Anthocyanins: Reversible versus the Irreversible Chemical Processes.
J Agric Food Chem
; 70(2): 656-668, 2022 Jan 19.
Article
in En
| MEDLINE
| ID: mdl-34982560
ABSTRACT
The kinetics and thermodynamics of the pH-dependent reversible and irreversible processes leading to color fading of pelargonidin-3-O-glucoside, peonidin-3-O-glucoside, malvidin-3-O-glucoside, and cyanidin-3-O-glucoside dyes in aqueous solutions are reported. Following the addition of base to the flavylium cation, the quinoidal bases disappear by three distinct steps:
(i) in an acidic medium by a biexponential process, in which the faster step is controlled by the hydration reaction and the slower one by cis-trans isomerization; the degradation process occurs essentially from the anionic quinoidal base; (ii) in a basic medium (pH > 9.5), in which the disappearance of the anionic bases is monoexponential, with the rate proportional to the hydroxyl concentration (hydroxyl attack), leading to anionic chalcones (cis and trans) at equilibriumâthe slower degradation step occurs from the di- and trianionic chalcones; and (iii) in the pH region circa 7.7 < pH < 9.5, in which hydration and hydroxyl attacks are much slower than anionic quinoidal base degradation (which is the rate-controlling step) and the equilibrium cannot be attained.Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Chalcone
/
Anthocyanins
Language:
En
Journal:
J Agric Food Chem
Year:
2022
Document type:
Article
Affiliation country:
Portugal