Influence of Cultivar and Growth Stage on Pigments and Processing Factors on Betacyanins in Red Amaranth (Amaranthus tricolor L.)

Abstract

Seven cultivars of red amaranth (Amaranthus tricolor L.) with different leaf color were evaluated for their betacyanin and chlorophyll content at two stages of development. The effects of food processing factors such as thermal treatment, light, H 2 O 2 , and prolonged storage on betacyanin extracts were also examined. Betacyanin concentrations were highly correlated with the leaf color index and the cultivars (Rocto joba, BARI-1, and Altopati) with better color index tended to be associated with high betacyanin. Within a shoot canopy, the apical leaves accumulated higher betacyanin than those of middle and basal leaves. While the highest concentrations of chlorophyll were found in BARI-1, however Red queen had the lowest concentrations. Color index of leaves and betacyanin concentrations were increased and chlorophyll concentrations were decreased with the plant age, which indicate that change of these colorant pigment concentrations with plant age enhance the red leaf formation in red amaranth. Low temperature, darkness, and free or low oxidants maintained the stability of betacyanin concentrations of red amaranth; prolonged storage degraded the betacyanin. Variable factors such as the cultivar of red amaranth, its degree of maturity, and the food processing factors have been shown to have a quantitatively important influence on betacyanin yields and preservation.