In Vitro Digestion of caseinate and Tween 20 Emulsions

In vitro digestion experiments are set-up with emulsions stabilized either with sodium caseinate and/or Tween 20, in the presence of mucin in the simulated GI fluids. The progress of charge alterations, focculation and coalescence are continuously monitored during the emulsions’ translation in the different stages of the model mouth–stomach–intestine cascade. Caseinate-stabilized emulsions become heavily flocculated and eventually coalesced into the gastric area. The causes of flocculation can be differentiated from those of coalescence: The former is due to electrostatic charge screening below the protein pI; while the latter is due to the action of gastric pepsin. Tween 20 is largely insensitive to pH changes and pepsin action, so its emulsion remains stable throughout the gastric area. Emulsions with mixed tween 20 and caseinate interfacial layers coalesce due to enzymic cleavage of caseinate, decreasing their interfacial area until the surface concentration of Tween 20 becomes large enough as to provide stabilization. The above can provide insight for the functionalization of protein and small-molecule emulsifier emulsions.