99E-27

P. Elez-Martínez and O. MARTÍN-BELLOSO. Dept. of Food Technology, UTPV-CeRTA, Univ. of Lleida, Av. Alcalde Rovira Roure, 191, 25198 Lleida, Spain

Knowledge of enzyme inactivation levels by High Intensity Pulsed Electric Fields (HIPEF) is necessary to achieve enzymatic stable products without over-processing. Therefore, models describing the inactivation of enzymes are useful to establish the appropriate HIPEF process conditions to obtain certain levels of inactivation. The purpose of this study was to propose mathematical models that could describe the orange juice peroxidase (POD) inactivation during HIPEF treatments. Orange juice was processed in a bench scale continuous flow mode HIPEF equipment. Freshly-squeezed orange juice was treated at electric field strengths (E) from 5 to 35 kV/cm up to 1500 μs of treatment time (t) using square wave pulses of 4 μs width at 200 Hz frequency applied in monopolar and bipolar mode. Experimental data were fitted to first-order fractional conversion (FCM) and Fermi's models (FM), and Weibull distribution function (WDF). Fitting accuracy was evaluated through the determination coefficients (R²) and the accuracy factors (A_f). WDF exhibited huge capacity to predict POD activity with the variation of t (R²>0.866) and A_f-values are close to 1. R² indicated that FM as fitted explained between 85.3 and 98.7% of the variability in relative activity (RA) and A_f-values ranged from 1.054 to 1.472. Relationships between model parameters and HIPEF processing factors were observed (p<0.05). The final values of RA from FCM decreased linearly with E and k₁ increased exponentially with E. The critical level of E of FM showed an inverse dependency with t. The mean to time and the mean to electric field strength to inactivate of WDF decreased with E and t, respectively. WDF and FM were the models that more accurately described the orange juice POD inactivation by HIPEF as a function of t and E, respectively. This study would be useful to determine the optimal operation HIPEF-conditions to achieve a POD inactivation level.

Session 99E, Nonthermal Processing: General II
8:30 AM - 12:00 PM, Wednesday AM Room Hall I-2

2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana