Thermal and pressure-temperature degradation of chlorophyll in broccoli (Brassica oleracea L italica) juice: A kinetic study

Heat and combined pressure-temperature degradation of chlorophyll in brocco li-juice have been studied on a kinetic basis. A treatment at 100 degrees C and atmospheric pressure during 37 min resulted in a 90% decrease in total chlorophyll content of broccoli juice. An extreme pressure stability of bo th chlorophylls a and b at room temperature was observed. Significant reduc tions in chlorophyll content were noticed only when pressure was combined w ith temperatures exceeding 50 degrees C. Chlorophyll degradation reactions at atmospheric as well as at elevated pressures could be adequately describ ed by assuming a first-order decay. Chlorophyll a degradation occurred more rapidly as compared to chlorophyll b degradation under all pressure-temper ature combinations tested (1-800 MPa/50-120 degrees C). Degradation rates i ncreased with temperature according to the Arrhenius law at all pressures t ested.