Thermal stability comparison between 10-catechyl-pyranoanthocyanins and anthocyanins derived from pelargonidin, cyanidin, and malvidin

Abstract

10-Catechyl-pyranoanthocyanins are pigments derived from nature formed by reacting an anthocyanin with caffeic acid. Here, we compared the thermal stability and formed degradation compounds of different 10-catechyl-pyranoanthocyanins. Pelargonidin-3-glucoside, cyanidin-3-glucoside, malvidin-3-glucoside, anthocyanins differing in the number of substitutions on the B-ring, and their corresponding 10-catechyl-pyranoanthocyanins were heated at 90 °C for 4.5 h at pH 3. Anthocyanin's color faded (ΔE_Lab > 5) after only 0.5 h, and absorbance at λ_vis-max decreased by > 64 % after 4.5 h, with cyanidin-3-glucoside being the most stable. In contrast, 10-catechyl-pyranoanthocyanins color was heat stable (ΔE_Lab < 5) with absorbance at λ_vis-max reduced by < 10 % after 4.5 h heating. A phenolic degradation compound formed in all samples, dependent on the parent pigment's B-ring substitutions. All 10-catechyl-pyranoanthocyanins produced the same colored degradation compound (λ^max = 478 nm, m/z = 315), suggesting the B-ring was not attached. 10-Catechyl-pyranoanthocyanins displayed excellent thermal stability irrespective of the anthocyanin used for formation.

Keywords: B-ring substitutions; Color stability; LCMS; Naturally derived colors; Spectrophotometry; Thermal degradation.