Physicochemical and sensory properties of wheat-cassava composite biscuit enriched with soy flour

Abstract

Cassava (Manihot palmata) and soybean were processed into flours and used to substitute wheat flour as a composite flour. The wheat flour (WF) was substituted by cassava flour (CF) at levels of 0, 10, 20, 30, 40, 50, 60, and 70%; while the resulting composite flours at levels above 40% were replaced with 10% soy flour (SBF) to increase their protein levels for biscuit production. This study evaluated the physicochemical and sensory qualities of biscuits baked from the various formulations of the flours. The proximate composition, hydrocyanic acid (HCN), spread ratio, biscuit weight and sensory properties of the biscuits were measured. Trained panellist evaluated the differences in organoleptic properties using a consumer sensory panel. Colour, crispiness, taste and flavour of biscuit reduced with increase in cassava flour but the diameter, spread ratio and shape of the biscuit improved. Increase in the levels of cassava flour resulted in decrease in the protein content progressively from 13.04% in 100%WF to 8.4% in biscuit with 40% cassava flour. However, addition of 10% soybean flour to composite flour above 40% CF resulted in progressive rise in the protein content of the biscuit from 8.41% in the 40% cassava flour biscuits to 11.39% in biscuits with 50%CF with subsequent reduction as the cassava flour increased to 70% level. The hydrogen cyanide content of the biscuits was increased with the increase in level of cassava flour in the formulations with maximum level of 0.20 mg/kg and in biscuit with 70% cassava flour. There was no significant difference in the overall acceptability between the biscuit from the control (100% wheat flour) and the composite flours up to 7040% cassava substitution level. Further addition of soy flour above 40%CF levels also improved the overall acceptability and there was no significant difference in the overall acceptabilitysensory qualities and other biscuit without soy flour enrichment up to 60% cassava flour. This indicates the feasibility of producing nutritious biscuits with desirable organoleptic qualities from cassava/wheat/soy composite flour up to 7060% cassava substitution level. Key words: Cassava, soybean, composite flours, biscuits, physicochemical and organoleptic qualities.