**8. Processing impacts**

The diversity in food, feed, and industrial used for soybean require the whole seed or seed components to be processed. Processing can affect the nutritional value of soybean protein and presence of amino acids in food and feed. Processing procedures can either separate seed components for different purposes or convert the entire seed into a product (usually human food). Some human soy foods such as edamame and soybean sprouts need little to no processing. Others including soymilk, tofu, natto, and soy sauce involve more processing. Soymilk and tofu processing are interconnected. Soymilk is a water-extract of whole or crushed soybeans that is coagulated and pressed into tofu [48]. While not all seed proteins convert into protein in tofu, 11S/7S storage protein ratios have been shown to be both positively and negatively correlated with tofu hardness [79, 80]. Natto is a soy food created by fermenting whole soybeans with *Bacillus subtilis.* Fermentation time affects final amino acid concentrations, and proper fermentation length could potentially increase nutritional values [81]. Soy sauce is produced by traditional and commercial methods, but both are based around whole seed or meal fermentation with *Aspergillus* sp. However, commercial methods have a lower amino acid to nitrogen ratio [48].

Soybean meal processing also impacts the level of amino acids in livestock feed. The first step in soybean meal processing is essentially separating protein from oil. A variety of methods exist including solvent extraction, screw pressing, and extruding [48, 82, 83]. All three processes have three final products: oil, meal (usually toasted to lessen anti-nutritional factors), and hulls. Over processing of solvent extracted soymeal has been shown to decrease lysine, cysteine, and arginine levels [84, 85]. Protein solubility and dispersibility measurements may be a useful indicator of over processing [86, 87]. Soybean hulls are sometimes added to livestock feed for additional fiber, however an increase in hull/meal ratios decrease the digestibility of amino acids [88]. While soybean is renowned for its protein and amino acid content, actual nutritional values can be decreased through certain processing methods.
