Effect of Roasting on the Nutritional and Anti-nutritional Properties of Soybean Seeds Grown in Kogi State, North Central Nigeria

Soybean is one of the most nutritionally complete legumes available to Nigerian food processors and consumers, yet its content of anti-nutritional factors, including trypsin inhibitors, haemagglutinins, and phytates, limits raw consumption. Roasting is a traditional processing technique widely used in rural communities to improve palatability and safety. This study investigated the effect of roasting temperatures of 150, 175, and 200 degrees Celsius at durations of 10, 15, and 20 minutes on the nutritional and anti-nutritional properties of soybean seeds sourced from Lokoja, Kogi State. Samples were roasted using an electric oven and analysed for crude protein, crude fat, crude fibre, ash, trypsin inhibitor activity, phytic acid, haemagglutinin activity, and protein digestibility. A factorial experimental design was applied. Results showed that roasting at 175 degrees Celsius for 15 minutes achieved the greatest reduction in trypsin inhibitor activity (76 percent) and phytic acid (48 percent) while preserving crude protein content at 36.2 percent. Higher temperatures caused significant protein denaturation and browning reactions that reduced digestibility. In vitro protein digestibility was highest at 175 degrees Celsius for 15 minutes (84 percent). The study recommends 175 degrees Celsius for 15 minutes as an optimal roasting protocol for soybean processing in cottage food industries across Kogi State. Keywords: soybean, roasting, anti-nutritional factors, protein digestibility, Kogi.