Quality attributes of sweet potato flour as influenced by variety, pretreatment and drying method

The effect of pretreatment methods (soaking in water, potassium metabisulphite solution, and blanching) and drying methods (sun and oven) on some quality attributes of flour from ten varieties of sweet potato roots were investigated. The quality attributes determined were chemical composition and functional properties. Data obtained were subjected to descriptive statistics, multivariate analysis of variance, and Pearson's correlation. The range of values for properties of sweet potato flour were: moisture (8.06-12.86 ± 1.13%), starch (55.76-83.65 ± 6.82%), amylose (10.06-21.26 ± 3.92%), total sugar (22.39-125.46 ± 24.68 μg/mg), water absorption capacity (140-280 ± 26), water solubility (6.89-26.18 ± 3.80), swelling power (1.66-5.00 ± 0.50), peak viscosity (24.50-260.92 ± 52.61 RVU), trough (7.08-145.83 ± 34.48 RVU), breakdown viscosity (11.00-125.33 RVU), final viscosity (10.21-225.50 ± 60.55 RVU), setback viscosity (3.04-92.21 RVU), peak time (6.07-9.06 min) and pasting temperature (69.8-81.3°C). Variety had a significant (P < 0.001) effect on all the attributes of sweet potato flour. Pretreatment did not significantly (P > 0.05) affect moisture, fat and lightness (L*). Drying method did not significantly (P > 0.05) affect fiber and L*. The interactive effect of variety, pretreatment and drying method had a significant (P < 0.001) effect on all the attributes except fat and fiber. Total sugar correlated significantly (P < 0.01) with water solubility (r = 0.88) of the flour samples. Variety was a dominant factor influencing attributes of sweet potato flour and so should be targeted at specific end uses.