Color stabilization of malvidin 3-glucoside at a higher pH can be explained by self-aggregation of the flavylium cation and copigmentation with the Z-chalcone form. In the presence of procyanidin C2, the red color of oenin appears more stable. However, the HPLC chromatogram shows a decrease in the amplitude of the peaks of oenin and procyanidin C2. Concomitantly, a new peak appears with a maximal absorption in the red region. This newly formed pigment probably comes from the condensation of oenin and procyanidin C2.
^Houbiers, Chantal; Lima, João C.; Maçanita, António L.; Santos, Helena (1998). "Color Stabilization of Malvidin 3-Glucoside: Self-Aggregation of the Flavylium Cation and Copigmentation with theZ-Chalcone Form". The Journal of Physical Chemistry B102 (18): 3578. doi:10.1021/jp972320j.
^Malien-Aubert, C; Dangles, O; Amiot, MJ (2002). "Influence of procyanidins on the color stability of oenin solutions". Journal of agricultural and food chemistry50 (11): 3299–305. PMID12010001.
^Sarni-Manchado, Pascale; Cheynier, Véronique; Moutounet, Michel (1997). "Reactions of polyphenoloxidase generated caftaric acid o-quinone with malvidin 3-O-glucoside". Phytochemistry45 (7): 1365. doi:10.1016/S0031-9422(97)00190-8.