Total anthocyanin content was determined in the purple carrot samples of Purplesnax and INTA44 by the pH-differential method, according to Giusti and Wrolstad [39 (link)]. Briefly, two dilutions (1/100) of the extracts were performed, one with potassium chloride buffer (pH 1.0), and the other with sodium acetate buffer (pH 4.0). Absorbance readings at 530 and 700 nm for each dilution were obtained after 15 min of incubation. The total anthocyanin concentration in the original sample was calculated using the following equation:
Total anthocyanin content (mg L−1) = (A × MW × DF × 1000)/(ε × 1); where A is the absorbance, MW is the molecular weight, DF is the dilution factor, ε is the molar absorptivity, and 1 is the optical path length. A commercial standard of cyanidin-3-glucoside (Sigma-Aldrich, Inc., Atlanta, GA, USA) was used as a reference (MW = 449.2 g mol−1, ε = 34,300 L mol−1 cm−1) to estimate total anthocyanin concentration, expressed as mg of cyanidin-3-glucoside equivalents per kg−1 fw.
Total anthocyanin content (mg L−1) = (A × MW × DF × 1000)/(ε × 1); where A is the absorbance, MW is the molecular weight, DF is the dilution factor, ε is the molar absorptivity, and 1 is the optical path length. A commercial standard of cyanidin-3-glucoside (Sigma-Aldrich, Inc., Atlanta, GA, USA) was used as a reference (MW = 449.2 g mol−1, ε = 34,300 L mol−1 cm−1) to estimate total anthocyanin concentration, expressed as mg of cyanidin-3-glucoside equivalents per kg−1 fw.