Physicochemical and microbial properties of orange-fleshed sweet potato flour produced with sun-drying and sulphiting agent

Abstract

Many local Nigerian processors of sweet potato flour use sun-drying of the sliced roots in place of modern mechanical drying. This study used carotene-rich UMUSPO3 orangefleshed sweet potato (OFSP) variety that was newly bred at National Root Crop Research Institute (NRCRI), Umudike, Nigeria to evaluate the possible effect of sun-drying and sulphiting on the physicochemical and microbial properties of OFSP flour samples. Data were obtained for OFSP sun-dried flour samples processed by different pretreatment methods (blanching, sulphiting with sodium metabisulphite and a control). Results showed that the bacterial and fungal load of the sulphite-flour sample was 8.5×104 CFU/g and 4.00×104 CFU/g while that of the control flour sample was 12.00×104 CFU/g and 6.50×102 CFU/g respectively. The total carotenoid content (TCC) of the flour samples ranged from 10.73 – 11.68 mg/100 g while the TCC of the fresh (unprocessed) OFSP was 40.20 mg/100 g on dry matter basis. The proximate composition of the flour samples was 10.21 – 10.95% moisture, 8.18 – 8.20% protein, 2.40 -2.55% fibre, 0.95 -1.11% fat and 1.73 – 1.85% ash. Obtained physico-functional properties were 13.17 – 13.23 g/mL swelling power, 2.70 – 3.4 g/mL oil absorption capacity, 2.65 – 2.85 g/mL water absorption capacity, 77.50 – 88.000C gelatinization temperature and 0.65 – 0.66 g/mL bulk density