Colour degradation and rheology of green chilli puree during thermal processing

Abstract

Abstract The kinetics of degradation of both green- and total-colour of green chilli puree was studied at selected temperatures (50–90 °C). A fractional conversion concept was applied to determine the kinetic parameters. The degradation of green- and total-colour followed first order reaction kinetics. In the case of green colour the data was based on changes in Hunter –a value while L × a × b was found to adequately represent total colour change. Dependence of the rate constant during heat treatment obeyed the Arrhenius relationship. The activation energy values for green- and total-colour degradation were 23.04 and 25.02 kJ mol–1, respectively. These results indicated that total colour should be used as the quality indicator during thermal processing of green chilli puree. The pungency of green chilli puree decreased during thermal processing as the capsaicin content was reduced from 559 to 441 μg g–1 while the Scoville heat unit decreased from 8500 to 7480. The puree behaved as a shear-thinning fluid and the flow activation energy at 100 r.p.m. equalled 19.22 kJ mol–1.