Physicochemical properties and metabolic effects of cowpea protein isolate

This study aimed to characterize the physicochemical properties, protein quality, and metabolic and intestinal parameters associated with the consumption of cowpea protein isolate (CPI). CPI was obtained by alkaline extraction, followed by isoelectric precipitation and freeze-drying. Its proximate composition, bioactive compounds content, and thermal, morphological, optical, and color properties were evaluated, along with amino acid profile, chemical score, and true digestibility. Male Wistar rats were fed with experimental diets containing 9% protein for 30 days. CPI showed high protein content (86.46%), total phenolics (1.79 mg GAE·g^-1), and 0.36 IU·mg^-1 of trypsin inhibition. Electrophoresis revealed predominant bands between 50 and 75 kDa and an endothermic peak at 83 °C. Tryptophan, methionine, and cysteine were identified as limiting amino acids, supplying approximately 70% of nutritional requirements. In vivo analyses showed that CPI presented protein efficiency ratio higher than 2.75, net protein ratio of 3.55, True Digestibility of 89%, decreased LDL-c, triglycerides, and Castelli Index II. Regarding intestinal health, CPI preserved acetic and propionic acid production and reduced butyric acid, aminopeptidase, sodium-glucose cotransporter 1, and sucrase-isomaltase gene expression while maintaining Peptide transporter 1 levels. Further, CPI decreased superoxide dismutase activity and malondialdehyde content, increased claudin and zonulin gene expression, and decreased occludin gene expression. Overall, CPI demonstrated good nutritional properties, supported efficient protein utilization, and improved lipid and oxidative parameters. However, some intestinal effects suggest potential limitations related to bioavailability and epithelial function under the conditions tested.