Kinetics of textural and color changes in green asparagus during thermal treatments

The textural and green color degradation of asparagus were determined after heat treatments at temperatures between 70 degrees C and 98 degrees C for selected time intervals. Maximum shear stress required to cut through green asparagus and the hue angle of the spear surface color were selected to represent the textural and color changes in thermally treated asparagus. Thermal softening of asparagus followed a first order kinetic reaction. The activation energies for softening of asparagus were 24.0 +/- 0.5 kcal/mol and kinetic reaction rates (k(84 degrees C)) ranged from 0.016 min(-1) at the butt segment to 0.027 min(-1) at the bud segment of the spears. Green color changes of asparagus spear surface followed a first order reaction. The activation energies for green color degradation of asparagus were 13.1 +/- 0.2 kcal/mol and kinetic reaction rates at 84 degrees C were 0.0066 +/- 0.0002 min(-1). (C) 2000 Elsevier Science Ltd. All rights reserved.