Some quality properties of yellow-fleshed sweet potato flour as affected by different drying methods

Abstract

This study compared some quality properties of yellow-fleshed sweet potato flour samples as affected by pretreatments (0.02% sulfite; blanching 85 °C for 3 min 30 s and steam blanching 100 °C for 2 min) and drying methods (oven, sun, and drum drying). The physicochemical composition, functional properties, pasting profile, and least gelation concentration of the flours were determined. Before pretreatment, the sweet potato tubers were sorted, weighed, rinsed, peeled, and diced. The smallest particle size (58 μm) was recorded for samples blanched at 85 °C followed by oven drying while drum-dried samples had the largest particle size (119.5 μm). The pH values (5.58 - 5.90) of the pretreated sun- and oven-dried samples were significantly (p<0.05) impacted by 0.02% sulfite. Compared to other drying methods. drum-dried samples had low bulk density (0.36 g/ml), the highest water (531%) and oil absorption capacities (168.5%,) and the least dispersibility (35%). Drum-dried samples had the highest swelling capacities at 60 – 80 °C but the values decreased at 80 – 90 °C compared to samples from other drying methods that had low swelling capacity at 60 - 70 °C but the values increased as the temperature increased from 70 – 90 °C. Results of the sample pasting profiles showed that pretreatment and drying techniques were significant on the various viscosities measured. Drum-dried samples had the lowest trough viscosity (18.13 RVU), final viscosity (24.88 RVU), setback viscosity (6.75 RVU), peak time (1.07 min), and pasting temperature (0 °C). This study concluded that the pretreatment and drying methods affected the quality properties of the yellow-fleshed sweet potato flour samples differently, consequently altering their functionality.Graphical