Rheological characteristics and kinetics of colour degradation of green chilli puree

Rheological characteristics as a function of particle size at 25 degrees C and the effects of pre-treatment and temperature on colour degradation kinetics of green chilli puree were investigated. Green chilli puree behaved as a shear-thinning fluid and the power law described well the shear stress-shear rate behaviour. The consistency index (K) decreased while the flow behaviour index (n) increased as the particle size of the puree decreased. The results indicated that colour degradation during thermal processing of chilli puree followed a first-order reaction kinetics. The combination L x a x b closely described the colour degradation behaviour. Dependence of the rate constant during thermal processing of chilli puree obeyed the Arrhenius relationship. The activation energy values for water-blanched and lye-treated chilli puree were 11.4 and 16.0 kJ/g mol, respectively. Lye treatment resulted in retarding the colour degradation rate. (C) 2000 Elsevier Science Ltd. All rights reserved.