Effect of hot air temperature on drying kinetics of palmyra (Borassus aethiopum Mart.) seed-sprout fleshy scale slices and quality attributes of its flour
Joseph Kudadam Korese, Matthew Atongbiik Achaglinkame, Solomon Kofi Chikpah
Abstract
This study investigated the influence of different drying air temperatures (40, 50, 60 and 70 °C) on moisture removal ratio and drying rate of pre-cooked and uncooked palmyra (Borassus aethiopum) seed-sprout fleshy scale (SFS) slices and quality of the resultant flours. Through drying kinetic analysis, it was found that the drying process of pre-cooked and uncooked palmyra SFS slices took place in the falling rate period and the drying time decreased with increasing air temperature in all samples. The colour parameters (L*, a* and b*) were affected by the drying air temperature and treatment type (pre-cooked and uncooked), with significantly higher ΔE values in uncooked samples compared to the pre-cooked samples. Drying of uncooked SFS slices maintains relatively high total antioxidant activity and low content of vitamin C compared to the pre-cooked samples. Beta-carotene, total phenol and total flavonoid contents however showed no specific trend in pre-cooked and uncooked SFS samples. Generally, pre-cooking palmyra SFS before drying significantly (P ˂ 0.05) improved their water absorption capacity, swelling index and swelling capacity while decreasing bulk density. However, treatment type and drying air temperature was observed to greatly (P ˂ 0.05) influenced all pasting properties without any observable trend. Based on the results, the quality of palmyra SFS flour showed opposite behaviours, thus indicating a compromise decision on processing conditions involved to meet the quality properties of interest.