Soy protein is utilized heavily in human and animal nutrition, but the gross energy (GE) and amino acid (AA) content of soy dietary ingredients can vary based on soybean plant genetics, agronomic conditions and processing procedures. Knowing the AA and energy content of a soy product being used in a diet helps ensure that formulated diets meet nutrient requirements necessary for optimal performance and well-being. As such, the goal of the current research was to determine if near-infrared reflectance spectroscopy (NIRS) could be used to rapidly determine the GE and essential AA content of different types of soybean meal (SBM), as well as, isolated and concentrated soy protein products. For this research over 250 different soy samples were obtained including full fat SBM, mechanically and solvent extracted SBM, soy protein concentrates, and isolates with 68% of the samples being solvent extracted SBM, the most utilized dietary soy product. Each sample was uniformly ground before obtaining a complete near-infrared spectral analysis using a Bruker MPA: FT- NIR Spectrometer equipped with OPUS software. Approximately half of the samples were used to construct calibration curves to predict the GE and essential AA content of the soy products, while the remaining samples were used to validate the calibration models. The crude protein content of the samples ranged from 36 to 88%. The coefficient of determination (R2) between the NIRS predicted values and the high performance liquid chromatography (HPLC) determined amino acid values or bomb calorimeter determined GE values were all 0.98 or greater except for tryptophan which had a value of 0.80. Furthermore, the NIRS- predicted values for all samples within the validation curves for the GE and essential AA methods deviated by less than 5% of the laboratory determined values, except for tryptophan. Due to the biochemical properties of tryptophan, the precision of determination via HPLC is reduced, which is reflected in decreased NIRS predictability. Overall, the results indicate that NIRS can be used to accurately predict the GE and total AA content of all the essential AA in SBM and soy protein concentrates and isolates with a comparable margin of error expected from traditional laboratory procedures.

Moss, D., T. Jones and A. Davis. 2025. The determination of gross energy and total essential amino acid content in soybean meal and soy protein concentrates and isolates by near-infrared reflectance spectroscopy. 2025 International Poultry Scientific Forum, Abstract M137.