**9. Evaluation methods**

All previously mentioned aspects of soybean production in regard to amino acid levels and human and animal nutrition depend on a single common denominator: amino acid quantification. Amino acids must be reliably, effectively, and accurately identified, measured and evaluated. A Google Scholar search of "amino acid analysis" will display over 1 million results. Several reviews have been published regarding the development of amino acid analysis [89–91]. In general, contemporary analysis of amino acids from any source will be performed by chromatography or near-infrared reflectance spectroscopy. Chromatography is the common method with specific techniques including ion exchange chromatography (IEC), high-performance liquid chromatography (HPLC), and gas chromatography (GC). HPLC is the more validated method for soybean amino acid analysis. It is more efficient than IEC, and it does not require the transformation into volatiles like GC [91–94]. Near-infrared reflectance spectroscopy (NIRS) is a more recent addition to amino acid analysis, and it has the potential to drastically improve the efficiency in soybean feed evaluation [19]. The inability to actually measure amino acid levels is main hindrance for NIRS amino acid analysis. NIRS methods must be developed from a calibration set of raw data (often from HPLC) [95–97]. Nonetheless, efficiency improvements should persuade researchers to continually explore future NIRS amino acid analysis applications.
