Effects of high hydrostatic pressure or high intensity electrical field pulse pre-treatment on dehydration characteristics of red paprika

The effects of various pre-treatments (hot water blanching, skin treatments, high pressure and high intensity electric field pulse treatment) on the dehydration characteristics of red paprika (Capsicum annuum L.) were evaluated and compared with untreated samples. Hot water blanching (100°C, 3 min) prior to dehydration (fluidised bed dryer at 60°C, 6 h and 1 m/s) resulted in the permeabilisation of 88% of the cell membranes in paprika, which in turn resulted in a higher mass and heat transfer. Skin treatments (such as lye peeling and acid treatment), as practised conventionally, increased dehydration rates but affected only the skin permeability. The application of high hydrostatic pressure (HHP, 400 MPa for 10 min at 25°C) or high intensity electric field pulses (HELP, 2.4 kV/cm, pulse width 300 μs, 10 pulses, pulse frequency 1 Hz) pre-treatments resulted in cell disintegration indexes of 0.58 and 0.61, respectively. Cell permeabilisation of these physical treatments resulted in higher drying rates, as well as higher mass and heat transfer coefficients, as compared to conventional pre-treatments.