Shredded and whole red pepper samples were dehydrated in a laboratory drier with a through-flow air velocity of 0.5 m s−1 at 50, 55, 60 and 70 °C. Shredded peppers dried faster than whole peppers. The drying behaviour of whole samples was characterised by a constant- and a falling-rate drying period, whilst that of shredded samples was characterised by a falling-rate drying period only. The mass transfer coefficient for whole samples during the constant-rate period was computed experimentally. The effect of temperature on the mass transfer coefficient was described by the Arrhenius model. The activation energy was 58 kJ mol−1. In the falling-rate period the mass transfer was described by a diffusional model, and the effective diffusion coefficient at each temperature was determined. Diffusion coefficients were estimated to lie between 4.38 × 10−11 and 10.99 × 10−11 m2 s−1 for whole peppers and between 37.23 × 10−11 and 99.61 × 10−11 m2 s−1 for shredded peppers. The effect of temperature on the effective diffusion coefficient was described by the Arrhenius equation, with an activation energy of 44 kJ mol−1 for whole peppers and 56 kJ mol−1 for shredded peppers.
© 2003 Society of Chemical Industry