Effect of heat and thermosonication treatments on peroxidise inactivation kinet...

• Autor(es): Cruz, Rui M.S. ; Vieira, Margarida C. ; Silva, Cristina L.M.
• Data: 2006
• Identificador Persistente: http://hdl.handle.net/10400.14/2854
• Origem: Veritati - Repositório Institucional da Universidade Católica Portuguesa
• Assunto(s): Watercress (Nasturtium officinale); Heat; Ultrasound; Inactivation; Peroxidase; Kinetics; Modelling
• Tipo de Documento: Artigo
• Idioma: Inglês

Descrição

The effect of heat and the combined heat/ultrasound (thermosonication) treatment on the inactivation kinetics of peroxidase in watercress (Nasturtium officinale) was studied in the temperature range of 40–92.5 C. In the heat blanching processes, the enzyme kinetics showed a first-order biphasic inactivation model. The activation energies and the rates of the reaction at a reference temperature for both the heat-labile and heat-resistant fractions were, respectively, Ea1 = 421 ± 115 kJmol 1 and Ea2 = 352 ± 81 kJmol 1, k184:6 C ¼ 18 14min 1 and k284:6 C ¼ 0:24 0:14min 1. The initial relative specific activity for both isoenzyme fractions were also estimated, being C01 = 0.5 ± 0.08 lmolmin 1mg protein 1 and C02 = 0.5 ± 0.06 lmolmin 1mg protein 1, respectively. The application of thermosonication was studied to enable less severe thermal treatments and, therefore, improving the quality of the blanched product. In this treatment the enzyme kinetics showed a first-order model. The activation energy, the rate of reaction at a reference temperature and the initial relative specific activity were, respectively, Ea3 = 496 ± 65 kJmol 1, k387:5 C ¼ 10 2min 1 and C03 = 1 ± 0.05 lmolmin 1mg protein 1, proving that the enzyme became more heat labile. The present findings will help to design the blanching conditions for the production of a new and healthy frozen product, watercress (Nasturtium officinale), with minimized colour or flavour changes along its shelf life.