Anthocyanins thermal degradation

The thermal degradation of anthocyanins, both in extracts and model systems, was reported to follow first-order reaction kinetics in all studies. The stability of anthocyanins and all pigments found in foods decreased with increases in temperature. 

Adams, J.B., Thermal degradation of anthocyanins with particular reference to the 3-glucoside of cyanidin. 1. In acidified aqueous solutions at 100°C, J. Set FoodAgric., 24, 747, 1973. 

After 8 hours of heating, anthocyanin solutions contain benzoic and cinnamic acids, dihy-droflavonols, catechins and a certain number of unidentified molecules. Furthermore, malvidin, the major component of wine coloring matter, has been found to be much more sensitive to thermal degradation than cyanidin (Table 6.4). The temperature factor should, therefore, be taken into account when wines are aging in barrels, vats or bottles, in order to protect their color. 

The temperature depends on the winery. Low temperatures are useful for precipitating unstable colloids. On the one hand, temperatures above 20°C promote the formation of carbocations from procyanidins, and therefore the TA complex (red, orange), as well as homogeneous polymerization. On the other hand, they also facilitate combinations with polysaccharides as well as color breakdown reactions. Furthermore, it promotes the thermal degradation of some anthocyanins, particularly malvidin. Alternating a low temperature with a temperature around 20°C promotes development, while maintaining it within certain limits. 

Sadilova, E. et al. (2007) Thermal degradation of anthocyanins and its impact on color and in vitro antioxidant capacity. Mol Nutr Food Res 51 (12), 1461-1471... 

The thermal stability of the anthocyanins from sunflower hulls (genotype Neagra de Cluj) extracted with SO2 in different concentration solutions was verified by heating for various durations at 65 to 95°C and at a pH range from 1 to 5. The degradation increased with the increasing of SO2 in the extraction solvent. "... 

Anthocyanins are included in the list of natural compounds known to work as powerful antioxidants. Blood orange anthocyanins are not very stable during thermal treatment and storage they can degrade and form colorless or undesirable brown-colored compounds the juice loses its bright red color and gains a brown color (Maccarone et al, 1985). 

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