Physicochemical Properties and Drying Characteristics of Pre-treated Okra Slices

Abstract

Okra (Abelmosclus esculentus) of regular slices (2mm) were pre-treated with NH₄HCO₃, sodium metabisulphite, trona, blanched and dried using  three drying methods – sun, solar and cabinet (at 55^oC, 65^oC, 75^oC). Two per cent (w/v) solution strength of each pre-treatment was used. Fick’s  diffusion and Arrhenius equations were used to model the drying characteristics and behaviour. Results showed that drying rate was highest at 75^oC in cabinet dryer and least at 55^oC. Pre-treatment did not affect  drying characteristics significantly but enhanced colour retention,  stabilization of vitamin C, texture softening and reduction in drying time. Ammonium bicarbonate was the most effective of all the pre-treatments in chemical retention irrespective of the drying method used. Activation  energy for control samples was the highest (10986.719 Cal/mol) while that of blanched samples was the lowest (6765.337 Cal/mol). The higher the temperature, the lower the equilibrium moisture content, the higher the angles of slide and repose. There was variation in high values of bulk density depending on the type of pre-treatment used with respect to drying method.