Extraction and Nutritional Value of Soybean Meal Protein Isolate

The increasing protein demand driven by global population growth necessitates the search for an alternative protein source. Soybean meal (SM), with approximately 47–49% proteins, is a viable option. Soymeal protein isolate (SMPI) is a cost-efficient protein source with a well-balanced amino acid profile, making it suitable for addressing this demand. This study attempts to address the lack of information regarding the extractability and nutritional potential of SMPI obtained utilizing a weak base and recoverable solvent. In this work, the structural and compositional studies of SMPI, as well as the aqueous extractability of ammonium hydroxide (NH4OH), are investigated. Furthermore, we examined the effects of heat treatment during oil extraction, where a comparison between protein isolates from soymeal and whole soybeans was carried out. The maximum extraction yield of 24.1% was achieved by increasing the concentration of NH4OH from 0.25–1%. In comparison to the soy protein isolate from whole soybeans (SPI), the compositional analysis report revealed that SMPI had higher levels of crude protein, moisture, and ash content, but lower levels of fat and carbohydrates. Furthermore, the examination of the amino acid composition confirms the existence of vital amino acids in SMPI. The amino acid score indicates that methionine, lysine, and threonine are the limiting amino acids. SMPI and SPI share structural and functional group similarities, as demonstrated by Fourier-transform infrared spectroscopy. Gel electrophoresis using sodium dodecyl sulfate–polyacrylamide shows that the protein molecular weight distributions of SPI and SMPI are similar. This in-depth evaluation emphasizes the advantages of SM by advocating its application in other sectors beyond conventional animal feed, such as nutritional supplements and bio-based products, and by improving the environmental sustainability and global food chains.