Physico-chemical Characteristics and the Effects of Processing Methods on the Nutritional and Anti-nutritional Quality of Soybean (Glycine max (L.) Merrill)

Abstract

The present investigation was carried out to determine the physico-chemical characteristics and effects of processing methods on the nutritional and anti-nutritional quality of soybeans. Soybean seeds were analysed using physico-chemical approaches, in order to obtain a detailed profile on these qualities. The effects of processing methods on the nutritional and anti-nutritional quality of soybean had an impact on the nutritional and anti-nutritional values. Soybeans were subjected to different processing methods which were sorted, washed, dried, and milled into flour (Sample A- Control), soaked in water (1:3) for 12h, mechanically dried at 60 ± 2 oC for 10 h and milled into flour (Sample B), soaked in water (1:3) for 12h, sprouted 72 h, mechanically-dried at 60 ± 2 oC for 10 h, roasted for 3 min and milled into flour (Sample C), boiled for 30 min in an open lid, mechanically-dried at 60 ± 2 oC for 10 h, roasted for 3 min and milled into flour (Sample D). The study revealed that raw soybean seeds had 90.43 ±3.93 g seed weight, 6.31 ± 0.41 mm length, 5.50 ± 0.29 mm breadth,4.58 ± 0.35 mm height, 0.88 ± 0.04 mm sphericity, 753.01 ± 6.62 kg/ m3 bulk density, 1181.03 ± 11.72 kg/ m3 true density, 36.33 ± 0.79 % porosity, 0.13 ± 0.005 g/seed hydration capacity, 1.25 ± 0.07 hydration index, 0.12 ± 0.01 mL swelling capacity, 1.62 ± 0.05 swelling index. The colour was recorded to be (L* 59.52, a* 8.97, b* 34.01), Chroma (c*) 35.17, and hue angle (ho) 9.84. After processing, moisture content increased (10.61 - 12.43 %), crude protein (42.97– 47.87 %), crude fibre (9.44 - 11.57 %), ascorbic acid (5.38 - 11.65 mg/ 100 g), and ash content (4.84-5.99 %) while total carbohydrates and total energy decreased significantly (17.70 - 15.92 %) and (439.69 - 397.82 %), respectively. Similarly, the phytic acid content decreased from 8.12 to 5.19 mg/100 g while the tannin decreased from 25.34 to 18.57 % and the protease inhibitor decreased from 7.12 to 5.01 %. The overall results of the current study revealed that the processing methods of soybeans had an impact on the nutritional and anti-nutritional values.  Further, the study showed that processing methods can significantly improve the nutritional qualities of soybeans while substantially reducing their anti-nutritional properties, thereby boosting the nutrients' bioavailability.