Evaluation of colour and stability of anthocyanins from tropical fruits in an isotonic soft drink system

Due to the growing market of food products associated to good health, the colour changes and stability of anthocyanin extracts from acerola, containing high level of ascorbic acid, and from açai, rich in flavonoids, were evaluated in an isotonic soft drink like system and in buffer solution. The degradation of anthocyanins from both sources followed first-order kinetics in all the systems, under air, either in the presence or absence of light. Addition of sugars and salts had a negative effect on the anthocyanin stability, being the rate constant (kobs) values in isotonic soft drink system 6.0 × 10− 2 h− 1 for acerola and 7.3 × 10− 4 h− 1 for açai, both in the dark. In the presence of light, the anthocyanin degradation was 1.2 times faster for acerola and 1.6 times faster for açai in soft drink isotonic systems, as compared to their respective buffer solutions. The highest stability observed in all açai systems was correlated to its high total flavonoid content and absence of ascorbic acid. The gradual degradation of red colour during storage of all systems was verified by the decrease of a⁎ values, accompanied with decreased colour intensity (decrease in C⁎ values) and tonality changes from red to yellow colour, as the h values increased during the experiment time.Industrial relevanceFunctional foods and addition of bioactive compounds to processed foods and drinks are a worldwide growing market. Thus, the aim of this study was to evaluate the stability of added anthocyanins from acerola and açai to an isotonic soft drink system and to study the effect of fluorescent light, mimicking the supermarket conditions, in such systems. Since colour is of fundamental importance for the acceptance of a food by consumers, the colour fading that occurs in these systems was also verified.