Abstract
Microwave and steam blanching as pretreatments to hot air drying of orange-fleshed sweet potato (OFSP) were studied. The air-drying experiment was performed at constant temperature of 70°C and airflow of 1.0 m/s. The effective moisture diffusivity varied from 1.5 × 10−9 to 4.4 × 10−9 m2/s, and 1.1 × 10−10 to 7.9×10−10 m2/s, for the microwave and blanched assisted hot air drying, respectively. The activation energy obtained for the various microwave-assisted hot air drying was 29.1 W/mm for 4 min, 68.1 W/mm for 3 min, and 79.7 W/mm for 2 min. Ascorbic acid degradation and formation of brown pigments in the OFSP slices were lower in microwave than in steam blanch-assisted drying. Microwave-assisted drying of OFSP is best governed by Page model, MR = exp(−ktn), while the blanch-assisted followed the logarithmic model, MR = a exp(−kt) + c. To produce better quality OFSP flour, it is recommended to cut the tubers into 3 mm slices, microwave at a power of 630 W for 2 min or blanch for 1 min, 43 seconds prior to hot air drying.
Highlights
Ghana is the third poorest country in the world with severe vitamin A deficiency (VAD) problems
Drying is among the best-known technologies used to produce quality products, which can be used as ingredients for the preparation of bread, banku, kenkey, and yoghurt, and to reduce postharvest losses associated with orange-fleshed sweet potato (OFSP) [6]
The objective of the present study was to investigate the effect of microwave and steam blanching pretreatment prior to air drying kinetics and quality attributes such as beta-carotene, ascorbic acid, and nonenzymatic browning of different slices of dried OFSP
Summary
Ghana is the third poorest country in the world with severe vitamin A deficiency (VAD) problems. Through an integrated agricultural and nutrition intervention biofortification programmes, the orange-fleshed sweet potato (OFSP) was introduced with the sole aim of combating the VAD problems in Ghana and many African countries. There are unsold orange-fleshed sweet potato roots by farmers who produce them especially during bumper harvest, because consumers complain of its undesirable soft texture after boiling, rendering boiled OFSP unappealing, making the produce go waste and unavailable year-round. The carotenoid in the OFSP is heat sensitive, and as a result, an appropriate method is required to preserve the orange color to produce high-quality products. The objective of microwave drying is to speed up drying process, increase mass transfer, and produce good quality products, while blanching prior to processing fruits and vegetables accelerates drying rate, prevents color changes, softens the texture, denatures enzymes, and destroys contaminating microorganisms. The objective of the present study was to investigate the effect of microwave and steam blanching pretreatment prior to air drying kinetics and quality attributes such as beta-carotene, ascorbic acid, and nonenzymatic browning of different slices of dried OFSP
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