Inactivation kinetics of peroxidase in zucchini (Cucurbita pepo L.) by heat and UV-C radiation

Abstract

The effect of traditional thermal water blanching, or its combination with a UV-C radiation pre-treatment (11 J/m 2 ), on the inactivation kinetics of peroxidase in zucchini ( Cucurbita pepo L.) was carried out in the temperature range of 80 to 98 °C, and up to 3 min of processing time. Peroxidase inactivation started being noticed only at temperatures around 85 °C. For both treatments, the inactivation kinetics followed a first order reaction with the Arrhenius model describing the temperature dependence of the reaction rate. The obtained kinetic parameters ( k Heat 89.6 °C = 7.37 × 10 − 7 ± 3.47 × 10 − 7 min − 1 and E a Heat = 925 ± 69 kJ mol − 1 ; k Heat 89.6 °C + UV-C = 2.42 × 10 − 5 ± 6.58 × 10 − 6 min − 1 and E a Heat + UV-C = 596 ± 48.8 kJ mol − 1 ) showed that UV-C radiation had a significant contribution to increase the peroxidase degradation rate. These results will help to design new pre-processing conditions for the production of frozen zucchini, using less severe thermal treatments and attempt to minimize quality losses. The use of UV-C radiation in processing creates novel methodologies, which can be complementary to classical techniques, providing reduced processing times and increased efficiency. Having been proved to be particularly useful in sterilization of liquids and surfaces, inhibition of microbial population and in decrease of protein synthesis, its application in combination with the traditional blanching may be in favor of less severe heating treatments. The evaluation of the kinetics of zucchini ( Cucurbita pepo L . ) peroxidase inactivation with the traditional blanching method and combined with ultraviolet radiation suggests that short UV-C treatments may be a useful non-chemical pre-freezing method, allowing the application of shorter blanching times, leading to a product with eventual higher quality retention which is highly relevant to industry. ► Heat blanching + UV-C above 85 °C promoted a synergistic effect on enzyme inactivation. ► Peroxidase heat + UV-C radiation inactivation in zucchini follows first-order kinetics. ► Addition of UV-C radiation to heat blanching favors a less severe blanching treatment. ► A UV-C radiation chamber was conceived by University of Algarve, Portugal.