Mathematical Modelling of Thermal Degradation Kinetics of Ascorbic Acid in Brassica Carinata

Abstract

Ethiopian green collard (Brassica Carinata) locally named yeabesha gomen is one of the important vegetable for ascorbic acid source in our society. However, adequate study has not been conducted to exploit the potential of this indigenous vegetable. The kinetics of ascorbic acid thermal degradation in yeabesha gomen as well as in pure ascorbic acid solution over a temperature range of 60–120oC (isothermal temperature process) for up to 60minutes has been studied. The thermal degradation of ascorbic acid in yeabesha gomen fitted first-order reaction kinetic model where the rate constant increased from 0.0146 to 0.051min-1 with an increase in the temperature from 60 to120oC respectively. The temperature dependence of degradation was adequately modeled by the Arrhenius equation with R2=0.977 and RMSE=0.0733. Activation energy for ascorbic degradation kinetics of yeabesha gomen was found to be 21.85kJmol-1. This lower activation energy value indicates that ascorbic acid in yeabesha gomen is quite susceptible to thermal processes. The outputs this work would be helpful to design and control practical thermal processing situations that minimize the loss of ascorbic acid in Ethiopian green collard as well as other leafy green vegetables contained ascorbic acid compounds.