Pressure‐Temperature Degradation of Green Color in Broccoli Juice

Abstract

Broccoli juice greenness was marginally affected by pressure at low temperatures (30-40°C). At 800 MPa and slightly higher temperatures (50-60°C), first-order degradation of green color was observed. The greenness loss was suggested to be due to chlorophyll-pheophytin conversion with no further pheophytin degradation. Pheophytin degraded further when higher temperatures ($70°C) were combined with elevated (or atmospheric) pressures (0.1-850 MPa). At these conditions greenness loss could be modeled by two consecutive first-order degradation steps. Temperature dependency of the rate constants for both degradation steps could be described by the Arrhenius equation with activation energies increasing with pressure. However, their pressure dependency could not satisfactorily be described by the Eyring equation.

Effect of microwave drying on quality kinetics of okra

“…The b à values decreased from 21.00 to 2.52, 5.05 and 7.15 at 440, 618 and 800 W, respectively. This might be due to decomposition of chlorophyll and carotenoid pigments, non-enzymatic Maillard browning, and formation of brown pigments during the process (Weemaes et al 1999). Those three final values of b à were significantly different.…”

Reaction Kinetics Analysis of Chemical Changes in Pressure-Assisted Thermal Processing

“…Upon heating, the central magnesium atom of the chlorophyll porphyrin ring is easily removed, forming pheophytin. Chlorophyll and green color changes in PATP-treated broccoli juice have been studied by van Loey et al [86] and Weemaes et al [93]. In the 200-800 MPa pressure and 30-80°C temperature range, van Loey et al [86] determined that temperature was the main factor affecting chlorophyll degradation while pressure had only a minor influence.…”

Kinetics of Crude Peroxidase Inactivation and Color Changes of Thermally Treated Seedless Guava (Psidium guajava L.)

“…Enzymatic browning is a serious problem because the oxidative enzymes such as peroxidase and polyphenolase may cause browning accompanied by changes in color, flavor, and nutritive value (Reyes and Luh 1960;Gónzalez-Barrio et al 2005). During thermal treatment, although these enzymes get inactivated, many other reactions such as decomposition of chlorophyll and carotenoid pigments (Kostaropoulos and Saravacos 1995;Lee and Coates 1999;Weemaes et al 1999), ascorbic acid browning (Salunkhe et al 1991;Ibarz et al 1999), and formation of brown pigments by non-enzymatic browning (Maillard) reactions take place and alter the color of the product (Rhim et al 1989;Lopez et al 1997). …”