Effect of Processing Techniques on Functional, Rheological and Sensory Properties of Different Varieties of Yam Flour (Water Yam, White Yam and Aerial Yam)

Yam (Dioscorea spp.) is an important tropical root crop widely cultivated in West Africa, serving as a major source of dietary energy, food security, and income. However, rapid postharvest deterioration and limited processing options restrict its utilization and commercial value. This study evaluated the effects of different processing techniques on the functional, rheological, and sensory properties of flours produced from water yam (Dioscorea alata), white yam (Dioscorea rotundata), and aerial yam (Dioscorea bulbifera). Fresh yam tubers were sorted, washed, peeled, sliced, and subjected to three processing methods: untreated (control), blanching, and natural fermentation before drying, milling, and sieving into flour. Functional properties, including bulk density, water absorption capacity, oil absorption capacity, swelling capacity, and solubility, were determined using standard analytical methods. Rheological properties, namely volumetric flow rate, viscosity, mass flow rate, specific volume, and specific weight, were evaluated using standard laboratory procedures, while sensory quality was assessed by a 20-member semi-trained panel using a nine-point Hedonic scale. Data were analyzed using one-way analysis of variance (ANOVA), and treatment means were separated using Duncan's Multiple Range Test at p < 0.05. Processing techniques significantly (p < 0.05) influenced the functional, rheological, and sensory properties of the yam flours. Fermentation improved bulk density and sensory quality, producing flours with the highest overall acceptability, particularly from water yam. Blanching enhanced oil absorption capacity and solubility, whereas untreated samples generally exhibited higher water absorption and swelling capacities. Rheological characteristics varied significantly among processing methods and yam varieties, reflecting differences in flour flow behaviour and handling properties. Overall, fermented water yam flour recorded the best quality attributes, including superior colour, taste, texture, flavour, and consumer acceptability, while aerial yam flour generally received lower sensory scores. The study demonstrates that fermentation is the most effective processing technique for improving the quality and utilization potential of yam flours. These findings provide valuable information for food processors and researchers seeking to develop high-quality flour-based products and promote the utilization and value addition of both conventional and underutilized yam species.