SUITABLE MODEL FOR THIN LAYER DRYING KINETICS OF WHITE AND PINK-FLESHED TANNIA (XANTHOSOMA SAGITTIFOLIUM) CORMELS

B. O. Oyefeso; A. O. Raji

B. O. Oyefeso Department of Agricultural and Environmental Engineering, University of Ibadan, Ibadan, Nigeria.
A. O. Raji Department of Agricultural and Environmental Engineering, University of Ibadan, Ibadan, Nigeria.

Keywords: Tannia cormels, Drying characteristics, Drying rates, Falling rate period, Diffusion mechanism, Modelling

Abstract

Drying is an essential unit operation in the conversion of fresh tannia (Xanthosoma sagittifolium) cormels into flour with the attendant benefits of improved shelf life and better storability. Information on the drying kinetics of the cormels will foster a good understanding of its behaviour during drying. Rate of moisture loss during the process can also be described by appropriate models. This study therefore, investigated the thin layer drying kinetics of two cultivars of tannia cormels at different temperature levels and determined the most suitable model for its prediction. White and pink-fleshed cormel slices of 3mm thickness were dried at 60, 70 and 80oC temperature levels. Data obtained from the drying experiments were fitted into ten selected models namely Newton, Page, modified Page, Logarithmic, Henderson and Pabis, Midilli, Verma, Two term, Thompson, and Wang and Singh models. The highest and the lowest drying rates were obtained at 80 and 60oC respectively. Page and modified Page models were the most suitable models for describing the drying behaviour of both tannia cultivars with highest R2 in excess of 0.9941 and lowest error estimates (RMSE≤0.0251; χ^2≤0.0008; MBE≤0.0060). The drying took place predominantly in the falling rate period which indicated that moisture removal from tannia cormels occurred mainly by diffusion mechanism.