The red color density of the films after exposure to indirect sunlight
was, as expected, quite dependent on the pomegranate juice
content. However, citric acid had a negative effect on this response,corroborating some previous studies which reported destabilization
of anthocyanins by citric acid (Buchweitz et al., 2013a;
Hubbermann et al., 2006), which Hubbermann et al. (2006)
ascribed to a high solvation capacity of citric acid, favoring stabilization
of the carbenium ion intermediately formed upon nucleophilic
attack of the flavylium cation, resulting in anthocyanin
decay.