Betalain Extracts from Beetroot as Food Colorants: Effect of Temperature and UV-Light on Storability

Beetroot is a good source of natural food colorants given that it contains significant amount of betalain pigments. This study investigates the three-months storage stability of betalain extracts recovered from unsold beetroot by a specific enzymatic mix. The extract storability was evaluated by the kinetic degradation model of betacyanins and betaxanthins, as well as by pigment color attributes (CIELa*b* parameters) under dark and UV-light exposure at different temperatures (4, 25 and 40 °C). Considering all the tested storage conditions, betaxanthins appeared to be more stable than betacyanins in terms of degradation rate constant, half-life time and activation energy. The effect of UV-light was negligible if the pigment was not exposed to temperatures higher than the room one, since no relevant differences were found between the parameters studied at 4 and 25 °C. Taking into account the visual color, all the investigated color indexes (total color difference, chroma and hue) were mainly affected by temperature, even if mildly high (40 °C), and to a lesser extent by UV-light exposure.