Modelling the Water Absorption Characteristics of Different Maize (Zea Mays L.) Types during Soaking

摘要

Water absorption characteristic of six different types of maize namely; dent corn (white and yellow), corn flour (white and yellow), popcorn and sweet corn during water soaking were studied at four different temperatures of 30, 40, 50 and 60°C.The water absorption data fitted very well into both Peleg’s and Becker’s models as to correspondingly determine the saturation moisture content (hydration equilibrium moisture content) and moisture diffusivity. The water absorption capacity and saturation moisture contents of each maize type increased as the water soaking temperature increased. The absorption kinetics followed the Fick’s law of diffusion during the first hours of soaking. The determined diffusion coefficients values varied from 10.6 to 13.5 × 10-11 m2/s for sweet corn, 6.74 to 8.88 × 10-11 m2/s for white flour, 5.27 to 7.09 × 10-11 m2/s for yellow flour, 4.44 to 5.79× 10-11 m2/s for popcorn, 4.25 to 5.69 × 10-11 m2/s for dent white corn and 3.28 to 4.68 × 10-11 m2/s for dent yellow corn, respectively. An Arrhenius–type equation was used to relate the moisture diffusivity (diffusion coefficient) of dent corn (white and yellow), corn flour (white and yellow), popcorn and sweet corn to temperature, and the energy of activation for dent corn (white and yellow), corn flour (white and yellow), popcorn and sweet corn was estimated. The values determined were 8.17, 9.59, 7.83, 8.45, 6.61 and 8.01 kJ/mol for dent white corn, dent yellow corn, white corn flour, yellow corn flour, sweet corn and popcorn, respectively.