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- Inactivation kinetics of peroxidase in zucchini (Cucurbita pepo L.) by heat and UV-C radiationPublication . Neves, Filipa I. G.; Vieira, M. M. C.; Silva, C. L. M.The effect of traditional thermal water blanching, or its combination with a UV-C radiation pre-treatment (11 J/m2), 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 (kHeat 89.6 °C = 7.37 × 10− 7 ± 3.47 × 10− 7 min− 1 and Ea Heat = 925 ± 69 kJ mol− 1; kHeat 89.6 °C + UV-C = 2.42 × 10− 5 ± 6.58 × 10− 6 min− 1 and Ea 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 response of watercress (Nasturtium officinale) to vacuum impregnation: Effect of an antifreeze protein type IPublication . Vieira, M. M. C.; Silva, C. L. M.; Cruz, R. M. S.The setting up of methodologies that reduce the size of ice crystals and reduce or inhibit the recrystalli-sation phenomena could have an extraordinary significance in the final quality of frozen products and consequently bring out new market opportunities. In this work, the effect of an antifreeze protein type I (AFP-I), by vacuum impregnation (VI), on frozen watercress was studied. The VI pressure, samples’weight, Hunter Lab. colour, scanning electron microscopy (SEM), and a wilting test were analysed in thiswork. The water intake of watercress samples augmented with vacuum pressure increase. The results also showed that, independently from the vacuum pressure used, the Lab. colour parameters between raw and impregnated samples were maintained, showing no significant differences (P > 0.05). A VI of 58 kPa, during 5 min, allowed impregnating the AFP-I solution (0.01 mg ml 1) into the water-cressb samples. The scanning electron microscopy (SEM) analysis showed the AFP-I impregnated frozen samples with better cell wall definition and rounded cell shape with smaller ice crystals compared with the control samples. The wilting test results corroborated that AFP-I is a valuable additive, since the leaves impregnated with AFP-I showed higher turgidity compared to the control samples. The present findings will help to better understand the effect of AFP-I, particularly, on frozen water-cress microstructure and its importance as valuable food additive in frozen foods and mainly in leafy vegetables.