In vitro gastrointestinal model for the elderly: Effect of high hydrostatic pressure on protein structures and antioxidant activities of whey protein isolate

With the increase in global life expectancy, the research on the specific digestive patterns of the elderly is becoming highly essential. We simulated the digestion process of older individuals in vitro and investigated the effects of various high hydrostatic pressure (HHP) treatments on the protein structure, digestibility, and anti-oxidant activity of whey protein isolate (WPI), as well as the antioxidant peptides produced from its digest. The HHP treatment specifically affected on the secondary and tertiary protein structures along with the free sulf-hydryl content of WPI. Protein microstructure revealed a significant increase in the number and depth of pores. Highest in vitro digestibility and cellular antioxidant activity was observed after HHP treatment at 600 MPa for 30 min. In the intestinal digest, 15 antioxidant peptides were identified whose characteristics matched those of bioactive peptides. Of these, the LGSDMEDLR peptide sequence had the highest "-CDOCKER Energy" and formed the salt bridge, attractive charge, conventional hydrogen bond, carbon hydrogen bond, and van der Waals with Arg380, Arg415, Arg483, Tyr334 and Asn382, which all located in the binding site of the Keap1-Nrf2 interaction. Overall, HHP appeared to be a potential method for the application of dairy products among the elderly.