Kinetic Parameter Estimation for Quality Change during Continuous Thermal Processing of Grapefruit Juice

Reaction order, activation energy (E a ) and average rate constant (k av ) were evaluated by dynamic modeling for color degradation of grapefruit juice during thermal processing. Simulated aseptic conditions were: 85–135°C, 40–175 set processing time, and average velocities 5–30 cm/set. Quality was assessed by nonenzymatic browning index (NEBI) and S‐hydroxymethyl‐furfural (HMF). Average values for reaction‐order and energy of activation were: 0 and 21.4 kcal/g‐mol (NEBI) and 0.3 and 23.2 kcal/g‐mol (HMF), respectively. These values were compared with those contained in the deformed ellipsoid which define the 90% joint confidence interval of all possible parameter combinations. Based on initial and final concentrations, the method can predict effects of processing on liquid foods.