Polyphenol oxidase inactivation in viscous fluids by ohmic heating and conventional thermal processing

This study investigated polyphenol oxidase (PPO) inactivation in a viscous solution of carboxymethyl cellulose (CMC) by ohmic processing (OH) and conventional thermal processing (CTP) at several temperatures and to assess the impact of CMC consistency on PPO inactivation. OH affects the PPO activity in temperatures higher than 50 degrees C (reduction to 20% at 50 degrees C, 12 min and complete inactivation after 2 min at 80 degrees C), whereas CTP caused a significant reduction in PPO activity only above 60 degrees C (reduction to 90% at 60 degrees C, 8 min and complete inactivation after 2 min at 80 degrees C). The rate of PPO inactivation by ohmic heating was higher than by CTP under all conditions tested, represented by a reduction of D-70 degrees C (OH: 3.61 min, CTP 7.32 min), except D-80 degrees C was similar to 0.5 for both techniques. The Z-value was higher for OH (14.68 degrees C) than for CTP (8.60 degrees C). Consistency did not have a major impact on inactivation rate. Practical Applications Inactivating enzymes that alter quality aspects of food products, such as polyphenol oxidase (PPO), is an important objective of a food processing technology. PPO is an enzyme commonly found in fruits and vegetables that catalyzes browning reactions. Ohmic heating (OH) is a technology known for its potential for processing highly viscous products. This study corroborates the potential of OH for processing highly viscous fluids over conventional thermal processing (CTP), having a great potential to be an alternative technique to food processing. In addition, it gave more evidence of the nonthermal effects due to the electrical current during the ohmic processing.