Control of Polyphenoloxidase and Peroxidase Activities in Mango and Papaya Juice by Pulsed Electric Field and Stevia rebaudiana Bertoni Extract Combined Process

In recent years, a possible alternative to complement the effectiveness of non-thermal technologies is to combine these technologies with the addition of additives from natural origin with antioxidant properties.

Stevia rebaudiana

Bertoni (

Stevia

) has antioxidant properties but no studies about its potential to enhance the effectiveness of pulsed electric fields (PEF) against some enzymes have been conducted to date.

Response surface methodology (RSM) was used to evaluate the simultaneous effects of electric field strength (from 20 to 40 kV/cm), treatment time (from 100 to 360

μ

s) and

Stevia

concentration (from 0 to 2.50% (w/v) on PPO and POD enzymatic activities of the juice under study.

The results obtained show that, only the highest PEF treatment tested (40 kV/cm; 360

μ

s) induced inactivation of both enzymes in the absence of

Stevia

. However, for any electric field intensity and treatment time combination, the complete inactivation of juice PPO was achieved only in presence of

Stevia

, regardless of the percentage added. On the other hand POD proved to be independent on

Stevia

concentration, but inversely dependent on electric field intensity (E) and treatment time (t). According to this, only in the case of the highest electric field tested (40 kV/cm)

Stevia

enhanced the POD inactivation percentage achieved by PEF.

These results show that

Stevia

could be useful in the food industry as natural antioxidant, preventing oxidative reactions, and its combination with PEF treatment could be a good strategy in reducing enzymatic activity improving at the same time the nutritional and physico-chemical quality of foods.