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 broccoli juice have been studied on a kinetic basis. A treatment at 100 °C and atmospheric pressure during 37 min resulted in a 90% decrease in total chlorophyll content of broccoli juice. An extreme pressure stability of both chlorophylls a and b at room temperature was observed. Significant reductions in chlorophyll content were noticed only when pressure was combined with temperatures exceeding 50 °C. Chlorophyll degradation reactions at atmospheric as well as at elevated pressures could be adequately described by assuming a first-order decay. Chlorophyll a degradation occurred more rapidly as compared to chlorophyll b degradation under all pressure−temperature combinations tested (1−800 MPa/50−120 °C). Degradation rates increased with temperature according to the Arrhenius law at all pressures tested. Keywords: Chlorophyll; broccoli ( Brassica oleracea L. italica ); kinetics; temperature; pressure