Intermolecular forces regulate in-vitro digestion of whey protein emulsion gels: Towards controlled lipid release

The utilization of emulsion-filled protein hydrogels for controlled lipid release in the gastrointestinal tract (GIT) displays great potential in drug delivery and obesity treatment. However, how intermolecular interactions among protein molecules influence lipid digestion of the gels is still understudied.

Differently structured whey protein emulsion gels were fabricated by heating emulsions with blocking of disulfide bonds (the "noncovalent" gel), noncovalent interactions (the "disulfide" gel), or neither of these (the "control" gel). The intermolecular interactions-gel structure-lipid digestion relationship was investigated by characterizing structural/mechanical properties of the gels and monitoring their dynamic breakdown in a simulated GIT.

Although the disulfide-crosslinked protein network formed thick interfacial layers around oil droplets and resisted intestinal proteolysis, the "disulfide" gel had the fastest lipolysis rate, indicating that it could not inhibit the access of lipases to oil droplets. In contrast, the "noncovalent" gel was more susceptible to in-vitro digestion than the "control" gel because of lower gel strength, resulting in a faster lipolysis rate. This demonstrated that intermolecular disulfide bonds and noncovalent interactions played distinctive roles in the digestion of the gels; they represented the structural backbone and the infill in the gel structure, respectively.