The effect of cowpea (Vigna unguiculata) flour as an extender on the physic-chemical properties of beef and hamburgers

This study was conducted in search of meat extenders/filler, which would minimize excessive bulging (swelling at the centre) of beef and hamburgers so as to enhance their use in sandwiches. The potential of dehulled cowpea flour was evaluated in beef and hamburgers, to determine its effects on the sensory, physical and chemical characteristics of these products. The Black-eyed cowpea (Vigna unguiculata) variety was steam treated at 100°C, dehulled, sundried for 48 hours and ground into flour. Boneless beef and pork (6kg each) were minced and apportioned into four groups of 1.5kg each for the preparation of the burgers. The beef and hamburgers were formulated separately at four levels of cowpea flour inclusions; T1 (control; no cowpea flour), T2 (5%), T3 (7.5%) and T4 (10%) of minced meat, on weight basis. All other ingredients were added in equal amounts to the minced beef and mixed in a mechanical mixer, after which they were moulded manually using a cylindrical tube into uniform shapes and sizes, and stored in a chest freezer for 12 hours to harden, after which they were bagged and stored for analyses. The weights, thicknesses and diameters of the products were taken before, and after cooking to determine the physical changes in them. The crude protein, fat moisture and lipid peroxidation of the products were determined. The burgers were grilled in an oven to a core temperature of 70°C and served to a 15-member taste panel for evaluation. The results indicate that cowpea flour in burgers increases the crude protein content, reduces the crude fat content and has no negative effect on sensory and lipid peroxidation of these products. There were reductions in product bulging and shrinkage with an increase in cowpea flour inclusion. Cowpea flour is recommended for inclusion in beef and hamburgers up to 10% on weight basis.