Studies on functionality of plantain-cowpea blends for extruded snacks

Abstract

Influence of functional and proximate properties of flour and blends of plantain and cowpea flour were determined to assess their suitability for making extruded snacks. The proximate and functional characteristics (Water absorption index, water solubility index and pasting) of the flour were determined. The rheological properties , protein, crude fiber and fat contents of blends of 90:10, 80:20, 70:30, 60:40 and 50:50 from the plantain and cowpea flours were determined. The influence of drying and extrusion on the functional properties of dried plantain and cowpea flours from different varieties was determined, along with their suitability for making extruded snacks. The varieties are: plantain (Apantu and Apem) and cowpea (Nhyira and Asetenapa), and there were significant differences (P<0.05) in both product varieties. The proximate composition, functional uniqueness, and rheological properties of dried plantain and cowpea blends (plantain: cowpea) 90:10, 80:20, 70:30, 60:40 and 50:50 were evaluated with the Brabender amylograph before extrusion cooking. For example, the rheological property peak paste viscosity in Brabender Units (BU) decreased from 595.5 BU for plantain, to 281.5 BU for plantain and cowpea (75:25%). Cowpea peak paste values were Nhyira 6 BU and Asetenapa 13BU. As the amount of cowpea in the plantain blends increased, the BU decreased. The extruded snacks were formulated from the plantain and cowpea flours at ratios of, plantains (75 to 100%), cowpea (0 to 25%), and oat fiber (0 to 25%) and extruded through a ZSK 30 twin-screw extruder at temperatures of 90 to 140 °C into half- and expanded- products. Pasting properties of the extruded blends determined with a Rotovisco Analyzer (RVA) were significantly different (P<0.05) among varieties. The peak viscosity for the extruded plantain was 6719.5 cP, blending with cowpea at 25 wt% reduced peak paste viscosity values to 4511.0 cP. Differences in rheological properties depended on plantain and cowpea varieties, and the paste property of extruded products was affected by the level of cowpea