Effect of heat and thermosonication treatments on watercress (Nasturtium offici...

• Author(s): Cruz, Rui M. S. ; Vieira, Margarida C. ; Silva, Cristina L.M.
• Date: 2008
• Persistent ID: http://hdl.handle.net/10400.14/2736
• Origin: Veritati - Repositório Institucional da Universidade Católica Portuguesa
• Subject(s): Watercress; Heat blanching; Thermosonication; Vitamin C; Kinetics modelling
• Document Type: Article
• Language: English

Description

The use of ultrasound in food processing creates novel and interesting methodologies, which are often complementary to classical techniques. In this work, the effect of heat and the combined treatment heat/ultrasound (thermosonication) on the thermal degradation kinetics of vitamin C in watercress (Nasturtium officinale) was studied in the temperature range of 82.5 to 92.5 °C. First order reaction kinetics adequately described the vitamin C losses during both blanching processes. The activation energies and the reaction rates at 87.5 °C for heat (H) and thermosonication (Ts) treatmentswere, respectively, EavitCH =150.47± 42.81 kJ mol⁻¹ and EavitCTs =136.20±60.97 kJ mol⁻¹, and K₈₇.₅ °CvitCH=0.75±0.10 min−1 and K₈₇.₅°CvitCTs=0.58±0.11 min−1. No significant differences (P>0.05) were detected between both treatments. The thermosonication treatment was found to be a better blanching process, since it inactivates watercress peroxidase at less severe blanching conditions and consequently retains vitamin C content at higher levels. The present findings will help to optimise the blanching conditions for the production of a new and healthy frozen product, watercress, with heat and a new blanching process methodology.