Casein structures differently affect postprandial amino acid delivery through their intra-gastric clotting properties

We aimed to assess if casein structure affects its digestion and its subsequent amino acid delivery kinetic. Higher nitrogen levels were recovered in dialysates after in vitro digestions of sodium caseinate (SC, formed of small aggregates) compared to micellar casein (MC, native form of casein) and calcium caseinate (CC, intermediate structure). Likewise, plasma indispensable amino-acid concentration peak was higher after SC compared to MC or CC ingestion in healthy volunteers in a randomized, double blind, cross-over study. In pigs, gamma -scintigraphy using labelled meals revealed that SC was mainly localized in the proximal part of the stomach whereas MC was distributed in the whole gastric cavity. Caseins were found in both solid and liquid phases and partly hydrolyzed casein in the solid phase shortly after SC drink ingestion. These data support the concept of slow (MC) and rapid (SC) casein depending of casein structure, likely due to their intra-gastric clotting properties.

Automated summary

This study aimed to evaluate the impact of casein structure on its digestion and subsequent amino acid delivery. The results showed that sodium caseinate (SC), formed of small aggregates, had higher nitrogen levels after in vitro digestion compared to micellar casein (MC) and calcium caseinate (CC). In a randomized, double blind, cross-over study with healthy volunteers, the peak concentration of indispensable amino acids in plasma was higher after SC ingestion than after MC or CC ingestion. γ-scintigraphy using labelled meals in pigs revealed that SC was mainly localized in the proximal part of the stomach while MC was distributed in the entire gastric cavity. Caseins were found in both solid and liquid phases, and partly hydrolyzed shortly after SC drink ingestion. These findings support the concept of slow digestion for MC and rapid digestion for SC, likely due to their intra-gastric clotting properties.