Studies on drying characteristics and physical quality evaluation of green peas

Fresh and blanched green pea (Pisum sativum L.) was dried at 55, 60 and 65°C in a through flow tray dryer with loading of 5.0 kg/m2. Physical characteristics of the peas were measured before and after dehydration. Four statistical models, which are semi-theoretical and/or empirical, describing thin-layer drying of biological materials have been investigated. A non-linear regression analysis using a standard statistical program was used to evaluate the constants of models. The results were compared for their goodness of fit in terms of coefficient of determination (r2), root mean square error (RMSE) and mean square of the deviation (χ2). The Midilli and Kucuk drying model was found most suitable for describing the convective drying curves of peas with a higher coefficient of determination varying from 0.997 - 0.999, lower RMSE from 0.0019 to 0.0165 and χ2 from 0.44E-06 to 4.90E-04 for different treatments. Blanching of peas in hot water prior to drying gave better rehydration ratio, coefficient of rehydration and percent of water assimilation. The colour change of peas during drying at different air temperatures followed first order reaction kinetics with a rate constant of 0.206 and 0.271/°C for blanched and unblanched samples, respectively. Sensory quality of blanched peas was better than unblanched samples.