Convective drying and quality attributes of elephant foot yam (Amorphophallus paeoniifolius)

The study evaluated the effects of convective hot air drying temperatures (40, 50, 60 and 70 degrees C) with different pre-treatments (Potassium metabisuiphite (KMS) and KMS + Citric acid) on drying as well as rehydration kinetics, color, texture and calcium oxalate content of elephant foot yam (EFY) cubes. Moisture diffusivity (6.69 x 10(-8)-3.41 x 10(-7) m(2)/s) and activation energy (25.18-32.46 kJ/mol) increased with pre-treatments and increase in drying temperature. Rehydration ratio increased with increase in drying as well as rehydration temperature compared to room temperature. Page and modified peleg models suited the best to describe drying and rehydration kinetics of EFY cubes, respectively. Color value 'L' decreased with increase in drying temperature and opposite trend was observed for 'a' and 'b' value. However the dried samples treated with KMS + blanching showed higher value and the highest L value (90.35) was observed at 50 degrees C. Sample hardness (94.34-349.57 N) and rupture energy (18.42-191.35 N/mm(2)) decreased with increase in drying temperature. Significant (p < 0.05) reduction in calcium oxalate (120-13.5 mg/100g) was observed during drying. Sample dried at higher temperatures had lower oxalate content and hardness which can be potentially used in curry making, bakery and confectionary products.