Efficient production of novel colorants for the food industry using 4-vinylgyauacol and cyanidin-derived anthocyanins

The food industry is transitioning towards naturally sourced colorants in response to consumer demand for healthier foods. Anthocyanins, pigments found in nature, can serve as naturally sourced options. However, they lack stability in many food systems. Pyranoanthocyanins, anthocyanin-derived pigments with improved stability, are promising alternatives; nevertheless, their scarcity and time-consuming formation limits their usage. Pyranoanthocyanins can be formed using hydroxycinnamic acids as cofactors, but formation is time-consuming. Decarboxylated hydroxycinnamic acids may be more efficient cofactors yielding pyranoanthocyanins in shorter times with higher yields, however studies on their usage for pyranoanthocyanin formation are limited. The objective of this research was to determine the most efficient anthocyanin-to-4-vinylguaiacol ratio for production of pyranoanthocyanins. Stock solutions of anthocyanins and 4-vinylguaiacol, decarboxylated ferulic acid (FA), were prepared with water at pH 3.1. Experimental solutions were prepared with final anthocyanin-to-cofactor molar ratios ranging from 1:1 to 1:30. A FA control was prepared at an anthocyanin-to-cofactor molar ratio of 1:30. Incubation was carried out at 45 °C for up to 96 hours. uHPLC-PDA-ESI-MS/MS was used to monitor pyranoanthocyanin formation every 24 hours. Incubation with 4-vinylguaiacol or FA resulted in the formation of new peaks in the uHPLC-PDA chromatogram. These peaks showed longer retention times, a hypsochromic shift in wavelength of maximum absorption, and increased mass-per-charge ratio consistent with 10-guaiacyl-pyranoanthocyanins. Yields with 4-vinylguaiacol were up to ~4 times greater than those with FA (8.1±1.9%). This efficiency was affected by the anthocyanin-to-cofactor molar ratio (p<0.01). Ratios of 1:5 and 1:10 resulted in highest (p<0.01) pyranoanthocyanin yields (31.0±1.1% and 25.1±0.4%, respectively). Pyranoanthocyanin formation with 4-vinylguaiacol followed pseudo-first-order kinetics model while with FA followed a ...