Ezekiel Tejumola Otunola, Johnson Adejuyitan, Ayoola Oluwagbenga Ojo:
Effect of Fermentation on some Properties of Sweet Potato Flour


Ladoke Akintola University of Technology, Department of Food Science and Engineering, Nigeria

Sweet potato, a potentially veritable and emerging source of valuable nutrients to many countries, and especially in the developing ones including Nigeria and many west African countries, was fermented in the laboratory by a modification of the traditional method usually employed in the southwestern part of Nigeria. Some of the properties of the resulting flour from fermentation were evaluated by standard and established methods, and then compared with those of the unfermented samples. Results obtained indicated that, while the crude protein and moisture contents of the flour from the fermented samples were significantly higher than found in unfermented samples, the contents of crude fat, fibre, ash and carbohydrate were less. Flour from the fermented samples had lower values of peak and final viscosities, water absorption capacity (WAC), bulk density and swelling power, but lower values with respect to the solubility and reconstitution indices, than those from the unfermented counterpart. The fermented sample also gave flour that was slightly more acidic. Flours from both samples took approximately the same time to reach peak viscosity and their pasting temperatures were not significantly different. Microbiological analysis indicated a predominance of lactic acid bacteria (LAB) in the fermented sample. The flour of the fermented sample, with its far greater load of LAB, but a significantly lower load of coliform bacteria than the unfermented counterpart, had no faecal coliforms. Sensory evaluation of the meals prepared from the two types of flours also indicated that the fermented sample was rated better in terms of overall acceptability. Fermentation could therefore lead to significant improvement in the nutritional status of sweet potato as revealed by the proximate composition. The products of such fermentation could also be safer microbiologically as revealed by the low coliform counts and the total lack of faecal coliforms. The fermented products also scored better generally in terms of sensory attributes. The pasting properties however revealed that more of the fermented samples may be needed to produce meals of comparable consistency to the unfermented samples.

Keywords: fermentation, flour, pasting, properties, sensory, sweet potato


Contact Address: Ezekiel Tejumola Otunola, Ladoke Akintola University of Technology, Department of Food Science and EngineeringOgbomoso, Nigeria, e-mail: eotunola@yahoo.com
Andreas Deininger, October 2010