Thermal degradation kinetics of total anthocyanins in açaí pulp and transient processing simulations

Abstract

The aim of this study was to investigate the thermal degradation of açaí pulp anthocyanins in experimental level and to simulate its degradation in a tubular pasteurizer starting from the transient regime. Thermal degradation was experimentally performed at 60, 70, 80, and 90 °C, in which samples were collected throughout 90 min. Anthocyanin concentration was determined using the differential pH method. The first-order kinetic model with low activation energy (42.8 kJ mol−1) and the thermodynamic parameters obtained (∆H > 0, ∆G > 0, and ∆S < 0) confirmed the high thermal stability of anthocyanin in açaí pulp. For the simulations, the mass and energy balances took into consideration a transient regime and also variation of anthocyanin concentration with the tube length. The finite difference method was used to solve the partial derivates. Were evaluated the effects of flow rate, solid content, heat exchange temperature, and tube length and diameter ratio. Our finds indicated that even considering the critical processing conditions, the losses of anthocyanins do not reach 1%, confirming its high thermal stability.