Effect of Radiant Energy on Anthocyanin Color Expression and Stability

As natural colorants get more attention in the food industry, efforts on anthocyanin (ACN) stabilization and color expression have increased for their incorporation in food products. Studies show enhancement of ACN performance via addition of stabilizing compounds (intramolecular copigmentation). The objective of this study was to investigate the impact of different light sources on the production of rare ACN pigments with enhanced performance. Light treatment of acylated ACN induces photoisomerization, which leads to change in ACN color expression. Pigments in ACN were extracted, semi-purified, and recovered in methanol. Extract aliquots in sealed quartz cuvettes were irradiated with varying light sources for up to 112 hours. Pigment isomerization was monitored over time by uHPLC-PDA-MS/MS. Cis- and trans-isomers of the pigments were isolated to compare their color stability and strength. The photoisomerization occurred the most with minimal pigment degradation with D65 lamp at 9.5 hours. In pH 4, trans-acylated delphinidin bleached completely, while its cis-counterpart exhibited color. In pH 5, cis- showed greater color intensity than the trans-isomer. In pH 7, the two isomers exhibited different hues. Thus, controlled light exposure produced cis-acylated ACN that exhibited a distinct color range from its trans-counterpart, and in pH ranges typically challenging for ACNs. This contributes to ACN’s role in making foods healthier and more visually appealing.