Physico-chemical Characteristics and the Effects of Processing Methods on the Nutritional and Anti-nutritional Quality of Soybean (Glycine max (L.) Merrill)
Caresma Chuwa
Tanzania Agricultural Research Institute (TARI) Ukiriguru, P.O. Box 1433, Mwanza, Tanzania.
Anju K Dhiman
Department of Food Science and Technology, Dr Yashwant Singh Parmar University of Horticulture and Forestry, Nauni, India.
Paul Saidia
Tanzania Agricultural Research Institute (TARI) Ukiriguru, P.O. Box 1433, Mwanza, Tanzania.
Abdulsudi Issa-Zacharia
*
Department of Food Science and Agro-processing, School of Engineering and Technology, Sokoine University of Agriculture, P.O. Box 3006, Chuo Kikuu, Morogoro, Tanzania.
*Author to whom correspondence should be addressed.
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.
Keywords: physico-chemical characteristics, processing methods, nutritional values, anti-nutritional quality, soybean