In vitro simulated digestion and Caco-2 cell absorption to explore potential of soy protein isolates as whey protein substitutes in canine and feline food

Digestive properties and bioavailability of soy protein isolate and whey protein in canine and feline were evaluated using in vitro simulated digestion and cell absorption experiments. The amino acids and peptides in soybean protein isolate and whey protein after digestion were detected by high-performance liquid chromatography and liquid mass spectrometry. Gastrointestinal digestion rates of soy protein isolate and whey protein were analyzed by fitting digestive kinetics curves. The degree of absorption and utilization of amino acids and peptides from the digestive products was evaluated by establishing a Caco-2 cell model. The results demonstrated that soy protein isolate, like whey protein, could produce large amounts of free amino acids and peptides distributed 100-1500 Da. The gastrointestinal digestion speed of soy protein isolate was similar with whey protein. It is worth noting from the intestinal absorption of Caco-2 cell that more than 15 amino acids produced by soy protein isolate and whey protein could be absorbed, and a large number of peptides were also utilized by Caco-2 cell. The bioavailability of soy protein isolates and whey protein for dogs respectively reached 6.30% and 9.00%, and it reached 7.40% and 16.40% in cats, respectively. Soy isolate proteins can be digested and absorbed by pets like whey proteins. These findings may provide significant strategies and support for the application of plant-based proteins in pet foods.