Modelling thermal degradation kinetics of Colour in curry leaf paste

Curry leaf, has been used as a food flavourant in Asian-Indian cuisine since ancient times. The colour degradation kinetics of curry leaf paste was studied using fraction conversion technique during thermal treatment at 50, 65, 80 and 95 °C for up to 60 min. Blanched, comminuted curry leaf paste was subjected to heat treatment at selected temperatures in awater bath with agitation. Treated samples were removed from the bath at selected time intervals (0–60 min after come-up period), cooled immediately and analyzed for colour using a Hunterlab colourimeter. Curry leaf paste colour was expressed in terms of tristimulus colour value a and combination (L,a,b). First order reaction kinetics adequately described the changes in colour values during thermal treatment of puree. The process activation energies were 29.3 and 22.1 kJ/mol, respectively, for a and (L,a,b) during thermal treatment. The Lab and TCD translate the real behavior of heat treated curry leaf puree. The retention of total colour of curry leaf paste may be used as a quality indicator for thermal processing conditions.