Alkaline and acid extraction of an L-tryptophan–sunflower flour red colorant: Production, characterization, and utilization

The objective was to produce and characterize a red colorant resulting from interaction of sunflower-derived chlorogenic acid with L-tryptophan/Trp and to evaluate its applications. Yield, intensity, solubility, stability, protein, and metal content of colorants from pH 9 and pH 11 lyophilized sunflower flour- Trp colorants were measured. Red color formation took <3 hours with alkalization and subsequent acidification. The sunflower flour: Trp mixture ratio that produced the greatest redness was 10:2. The highest red pigment was in supernatants and not the precipitates. The red colorant intensity and solubility were highest at neutral pH when compared to acidic pH solutions. The color stability of the new red colorant in icing and refrigerated whole milk matrices, when assessed weekly for a month, showed no color change in refrigerated milk. After 30 minutes of incubation at 63°C, pinkness in milk remained unchanged or increased. The pink color, however, faded in icing over time due to exposure to light. The present study established a new natural red colorant developed from sunflower protein-Trp mixtures at alkaline pH, as well as its application in icings and whole milk for commercial strawberry milk products. This colorant could serve as a replacement for the synthetic petroleum-based Red 3. • Sunflower flour was used as a source of chlorogenic acid reactant for red pigment. • Red pigments were in both precipitates and supernatants after isoelectric precipitation. • Supernatants exhibited higher soluble yield and redness than precipitate fractions. • The highest redness was in colors associated with the albumin protein fraction • Sunflower flour-derived colorant successfully colored icing and milk.