More Efficient Formation of more Stable Cyanidin-derived Food Colorants using 4-vinylphenol

Steven Cheng
Undergraduate (Food Science)
Dr. Monica Giusti
Food Science and Technology

Anthocyanins are dietary flavonoids with vivid colors found in plant tissues. Anthocyanin-rich juice-concentrates or extracts can be used as food colorants substituting artificial ones. Health concerns associated with the consumption of artificial colorants and an increased consumer demand have accelerated the transition towards colorants from natural sources. However, problems arise in the application of anthocyanins as food colorants due to their lack of stability. Pyranoanthocyanins (PACNs) are anthocyanin-derived pigments that bear a pyran ring in their structure, with enhanced stability. Hydroxyphenyl PACNs (HP-PACNs) are a class of PACNs found in wine resulting from the cycloaddition between hydroxycinnamic acids and anthocyanins. Nonetheless, their synthesis is expensive and time-consuming, restricting their use by the industry. The production of HP-PACNs with 4-vinylphenols, decarboxylated hydroxycinnamic acids, can occur faster. The objectives of this study were to determine the most efficient anthocyanin to 4-vinylphenol ratio for production of HP-PACNs, and to compare it with its precursor, p-coumaric acid. Black carrot anthocyanins were saponified, diluted in pH 3.1 HCl water and mixed with 4-vinylphenol in molar ratios of 1:1, 1:5, 1:10, 1:20, and 1:30. A positive control of anthocyanins with p-coumaric acid was prepared at a molar ratio of 1:30. PACN formation and remaining pigment were evaluated after incubation at 45°C for 24 hours in the dark using HPLC-PDA-MS analyses. PACN production with 4-vinylphenol was at least 34 times greater (p<0.05) than with p-coumaric acid (0.4%). Moreover, PACN yield with 4-vinylphenol at a molar ratio of 1:5 (36.3%), 1:10 (39.1%) and 1:20 (34.7%) was significantly higher than with 1:1 (14.0%) and 1:30 (28.7%). 4-Vinylphenol in a ratio of 1:5 and 1:10 had higher content of pigment remaining (~40%) than the anthocyanin without cofactor (22.4%), but lower than the p-coumaric acid control (45.4%). Overall, synthesis of PACNs using 4-vinylphenols was much faster than with p-coumaric acid, yielding ~40% PACN in 24 hours, and requiring less cofactor (1:10). Future studies will focus on evaluating different temperatures and pH to further optimize PACN synthesis. Ultimately, this will facilitate the transition from synthetic colorants to healthier alternatives for the food industry.