Changing colors and compositions of aqueous chaya leaf extract in relations to temperatures and storage time

Abstract

Aqueous chaya leaf extract has been used as food additive for improving taste and color of which the latter tends to change during storage. This research aim to study color changes and some components of the chaya extract kept between 5-25˚C for 10 days. The results showed that a* values as well as amounts of the total chlorophyll, and ascorbic acid continuously decreased from their initial values throughout the storage period especially when it storage in the high temperatures. The chaya extract kept at 25 ํC had only 3 days of self-life. The appearance of spoilage was observed from changing color to dark-brown color and precipitation. The results of kinetic studies on the quality attributed aforementioned found that the kinetic changes of those during the storage in individual temperatures were 1^st order kinetic reactions. These were well predicted by the first-order fractional conversion (FOFC) mathematical model given values of R² 0.63-0.99 and root mean square of error (RMSE) <2, except the RMSE of a* values estimated at 10 and 25°C which were higher than 2. Rates of the kinetic changes estimated using the FOFC model exponentially increased in relations with temperatures increased. The relationships were well predicted by the Arrhenius mathematical model of which the values of R² and RMSE were 0.76-0.99 and RMSE <2, respectively.