Characterization of pigments from cultivated Amaranthus species and assessment of their commercial applications as natural food colorants

Consumer demands for healthier foods with simple ingredients have evoked trends in the food industry to replace synthetically produced colorants with naturally derived alternatives. Of these, betalain pigments derived from beets (Beta vulgaris L.) serve as an important alternative to the synthetic dye FD&C Red 40 for many different low-acid food applications. Betalains are a versatile class of colorants, but their application can be undesirably expensive due to the limited production areas and high cost of red beets. Vegetable amaranth (Amaranthus spp.) is a particularly appealing alternative to beets because of its high concentrations of betacyanin pigments and status as a ubiquitous low-maintenance crop that is resilient to many of the environmental stresses that afflict traditional crops. Unlike beets, amaranth can be harvested multiple times per season and provide additional chlorophyll and carotenoid pigments from the same plant material. The work herein surveys a diverse collection of vegetable amaranth cultivars for pigment content, color, and composition and also tests their stability in a model beverage system. The highest average betacyanin content was 479 mg per 100g dry tissue from the accession PI 566897 (A. cruentus L.). No betaxanthins were detected in any of the accessions surveyed. The major betacyanin observed in all extracts was amaranthin (betanidin 5-O-β-glucuronosyl-glucoside). Consistent differences in betacyanin profiles were noted between different species. Color values for highly pigmented accessions indicated that amaranth extracts can provide bluer hues than current commerical options derived from beets. The highest total chlorophyll and carotenoid content was observed from accession PI 608661 (A .graecizans L.), with an average of 5123 μg of chlorophylls a+b per gram DT and 819 μg of carotenoids per gram of dry tissue. Five genotypes from this survey noted for their high betacyanin yields and phenotypic differences were grown under field conditions and used as colorants in a model beverage system to evaluate their real-life performance in comparison to current natural colorant options. In this research, the thermal and pH stability of five different amaranth cultivars along with crude and purified beet-sourced colorants were studied. Significant differences in pigment degradation rates and color parameters were observed between amaranth cultivars, with PI 689689 (A. spp.) showing the greatest stability and highest chroma (C*) values. This accession showed similar stability to beet-colored beverages at pH 3 and 4.5 and produced significantly bluer colors. Overall, beverages showed the best stability at the lowest temperature tested (5 °C) and generally had the slowest pigment degradation at a pH value of 4.5. HPLC-MS is currently being used to identify non-betalain extract components that significantly influence extract color and stability. Results indicate that certain Amaranthus cultivars can match the stability of beet-derived colorants and provide color hues unobtainable with beets alone. Overall, the studies described herein supply valuable baseline data that are necessary for understanding betalain biosynthesis in Amaranthus, implementing the use of Amaranthus pigments as natural food colors in a commercial setting, and informing breeding strategies to optimize pigment yield, stability, and color.LimitedAuthor requested closed access (OA after 2yrs) in Vireo ETD syste