Comparison of physical and chemical properties of wheat flour, fermented yam flour, and unfermented yam flour

Yam is a root and tuber climbing plant and main calorie source in some tropical regions of Africa. In this study, properties of fermented (brown) yam flour (FYF) and unfermented (white) yam flour (UYF) were compared with refined wheat flour (RWF). The yam flours were lower in protein (3.3%-5.9%), arabinoxylans (0.93%-1.40%), phytic acid (0.17-0.53mg/g), phenolic acids (0.57-2.28mg FAE/g), amylose (17.3%-22.6%), and fat (0.2%-0.4%) but higher in potassium 119-845mg/100g), ash (1.70%-2.21%), total starch (73.8%-74.2%) and fiber contents (6.8%-7.0%). All the samples exhibited high (>90) estimated glycemic index (eGI) values. However, FYF and UFY had significantly (p<0.05) lower eGI than RWF. Thermal studies showed that FYF and UYF required more energy for gelatinization than RWF. Compared to RWF, FYF swelled more rapidly and retrograded faster. FYF had significantly (p<0.05) higher gel firmness than RWF and UYF. Overall, the flours exhibited different characteristics which will impact functional and nutritional properties. Practical applicationsYam is a staple crop grown in tropical and subtropical Africa, the Caribbean, South Pacific, and Asia. Increased utilization of local staple crops in production of composite flours or in food products can increase economic gain for farmers and local economies. The study of the functional characteristics of the yam flours would allow for the development of tailor-made composite flours for production of many unique food products. These yam flours may also be of use in formulation of gluten-free products, especially products such as cakes and pastry that don't require high gluten strength.