Effects of Temperature and Steeping Time on the Proximate Compositions and Selected Physical Properties of Soybean Flour

Abstract

A study to investigate the effect of temperature (80, 85, 90, 95, and 100^oC)  and steeping time (12, 15, 18, 21, and 24 hours) on the proximate composition (ash, crude fibre, fat , protein, and carbohydrate) values (%) and physical properties (bulk density, packed density (g/ml), angle of repose (degrees), and particle size (µm)) on soybean flour was conducted. Response surface Methodology (RSM) was used for the work. Central Composite Design in Design Expert (version 6.0, 2002, Minneapolis, United States) computer software package was used to design the experiment. Analysis was also done and all results were presented with a three dimensional plot. The results showed that the moisture content of the soybeans flour ranged from 3.26 – 7.35, 3.40 – 4.50 for ash, 3.15 – 4.82 for crude fibre, 31.32 – 35.21 for protein, 19.37 – 22.65 for fat, and 29.66 – 35.19% for carbohydrate. Angle of repose for soybeans flour samples ranged from 33.15 – 38.16o, bulk density varied between   0.30-0.36, packed density varied between 0.52 – 0.57g/ml and   particle size distribution varied between 0.44 – .98µm for the different samples. It was observed that longer steeping time and drying temperature resulted to an increase in the protein content and decrease in crude fibre content. Conversely shorter steeping time and lower drying temperature resulted in an increase in the fat content. A nine-point hedonic scale on sensory and acceptability tests showed that sample soaked for 24 hours and dried at 90oC was most preferred in taste and overall acceptability.