Journal of Food Engineering 18 (1993) 159-179 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONM Prediction of the Effective Moisture DiR&ity in Gelatinized Food Systems G. K. Vagenas” & V. T. Karathanos Department of Food Science, Rutgers the State University, New Brunswick, New Jersey 08903, USA (Received December 1990; revised version received 11 November 199 1; accepted 3 February 1992) ABSTRACT Gelatinizedfood systems develop a porous structure during dehydration; therefore, the moisture diffusivity calculated from such experiments should be considered as an effectivediffusion coefficient. In this work, the effective moisture di@ sivity of gelatinized starches was determined from drying experiments using the method of slopes. A methodology is pre- sented which permits the calculation of the effective moisture di@ .sivity from the diffusion coeficients of the two phases (air-solid) and the poro- sity of the system. The dimsion coeflcient of the homogeneous solid phase (gel) was zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA estimated zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA from the calculated values of the effective di@ - sion coefficient, using non-linear regression analysis.Its value depends on the moisture content and temperature and varies in the range 1.4 x IO-” to 2.6 x IO-‘” m’ls for Amioca and 4.1 x IO-” to 32~ IO-r0 ml/s for Hylon 7. NOTATION a Empirical constant - (eqn (30)) a, Water activity zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA (-) A Frequency factor (m2/s) b Empirical constant ( 1fs) (eqn (28)) B Empirical constant (-) (eqn (6)) C Concentration ( kg/m3) *Present address: Department of Chemical Engineering, National Technical University GR- 157 73, Athens, Greece. 159 Journal of Food Engineering 0260-8774/92/$05.00 - 0 1992 Elsevier Science Publishers Ltd, England. Printed in Great Britain