Moisture diffusion modelling of drying in parboiled paddy components. Part I: starchy endosperm

Abstract

A non-dimensionalised isothermal liquid diffusion drying model in prolate spheroid geometry using prolate spheroidal co-ordinate system was developed, and applied to drying of parboiled polished rice. Using appropriate hydrothermal treatment the parboiled polished rice was prepared, and its drying characteristics were determined using fluidised bed drying at air temperatures varying from 50 to 100 ∘C. A mathematical model simulating the drying was solved using the finite difference methodology. The liquid diffusion coefficients of starchy endosperm of parboiled polished rice while drying with various air temperatures were determined by minimising the sum of squared differences between experimentally observed and model predicted characteristics. The developed models showed good agreement with the experimentally observed data. Temperature dependence of liquid diffusion coefficients was expressed by an Arrhenius type of equation, which had a high correlation coefficient: D vs =1.079706×10 −7 exp (−2036.252438/T a ) [ r=0.9887]