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 grape fruit juice during thermal processing. Simulated aseptic conditions we re: 85-135 degrees C, 40-175 sec processing time, and average velociti es 5-30 cm/sec. Quality was assessed by nonenzymatic browning index (N EBI) and 5-hydroxymethyl-furfural (HMF). Average values for reaction-o rder 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% j oint confidence interval of all possible parameter combinations. Based on initial and final concentrations, the method can predict effects o f processing on liquid foods.