Pressure-Temperature Degradation of Green Color in Broccoli Juice

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.