Extraction methods and nutritional characterization of protein concentrates obtained from bean, chickpea, and corn discard grains

Protein concentrates obtained from discarded grain flours of white chickpea Sinaloa (Cicer arietinum) (CC), “Azufrazin” bean (Phaseolus vulgaris) (BC), and white corn (Zea mays) (MC), were characterized biochemically through bromatological analyses (protein, lipid, fiber, moisture, ashes, and nitrogen free extract), HPLC techniques (amino acids content), and spectrophotometry (anti-nutrients: phytic acid, trypsin inhibitors, and saponins). The percentage of protein obtained from CC, BC, and MC was 71.23, 81.10, and 55.69%, respectively. Most peptides in the BC and CC flours had a molecular weight of <1.35 kDa, meanwhile, MC peptides were heavier (1.35 to 17 kDa). The amino acids (AA) profile of flours and protein concentrates were similar; however, all the protein concentrates showed an increased AA accumulation (300 to -400%) compared with their flours. The protein concentrates from BC registered the highest AA accumulation (77.4 g of AA/100 g of protein concentrates). Except for the phytic acid in CC and trypsin inhibitor in CC and MC, respectively, the rest of the protein concentrates exhibited higher amounts of the anti-nutrients compared with their flours; however, these levels do not exceed the reported toxicity for some animals, mainly when used in combination with other ingredients for feed formulations. It is concluded that CC and BC protein concentrates showed better nutritional characteristics than MC (level of protein, size of peptides, and AA profile). After biochemical characterization, protein concentrates derived from by-products have nutritional potential for the animal feed industry.