MODELING OF DISCOLORATION OF DRIED POWDER OF CARROTS

A model to represent the discolouration of dried powder of carrots as a function of temperature was developed. Two types of carrots, Asian a nd European, containing large amount of lycopene and beta-carotene, re spectively, were tested. The dried powder was stored under an atmosphe re with O-2 and at three different temperatures, 5, 20 and 35 degrees C. The surface colour of the powder nias monitored during storage by a Hunter colour ratio a/b. In the proposed model, the rate of oxidation was assumed to be represented by the product of the fraction of conce ntration of oxidized pigment at arbitrary time and a specific rate of oxidation of pigment. The rate parameters in the proposed model were c alculated by fitting the experimental data with smooth curves by trial and error at the end of the induction period but before discolouratio n took place. The frequency constant and activation energy, expressing the temperature dependence of the rate parameters, were expressed by the Arrhenius relation. The simulation results of a Hunter colour rati o a/b of dried powder at 25 degrees C showed good agreement with the e xperimental data, suggesting that the proposed model was effective for the prediction of discolouration of dried powder of both types of car rot. The use of the induction period in the manner described may enabl e the shelf life of dried powder to be predicted. (C) 1998 Silsoe Rese arch Institute.