THIN-LAYER DRYING CHARACTERISTICS OF TIGER NUT (CYPERUS ESCULENTUS) SEEDS

ABSTRACT The thin‐layer drying behavior of tiger nut seeds dried using hot air, solar drier and open sun drying was investigated. The drying took place in the falling rate period. Six thin‐layer drying equations were used to fit the drying data. For oven drying, the parabolic model had the highest correlation coefficients, R2 of 0.972 to 0.990 and the lowest Chi‐square value (χ2) of 0.000941 to 0.001463 and root mean square error (RMSE) of 0.028213 to 0.034594. The logarithmic model had the highest R2 (0.995 and 0.994) and the lowest χ2 (0.000446 and 0.000417) and RMSE (0.019869 and 0.019051) for sun and solar drying of tiger nut. The effective moisture diffusivity coefficient varied from 2.39 × 10−10 to 7.23 × 10−9 m2/s while the activation energy was 28.14 kJ/mol for oven drying of tiger nuts. This indicates that the diffusion process requires lower energy hence ease of drying of the tiger nut. PRACTICAL APPLICATION Tiger nut can be categorized as one of the lesser known and underutilized crops, which are potentially valuable as human and animal foods. Its proper processing will produce products that can be used to maintain a balance between population growth and agricultural productivity. Drying is a fundamental unit operation in the processing of this seed, which influences the physicochemical and quality characteristic of the product. An increase in the utilization of the crop and the formulation of a wide range of possible products from tiger nut will require that the traditional open‐air sun‐drying method be replaced with efficient drying systems. Therefore, an evaluation of the drying characteristics as a function of different drying conditions could help in predicting suitable drying conditions for good quality products.