Enzyme triggered release of aroma molecules from oil-in-water emulsions

The goal of this work is to demonstrate enzyme-triggered release of a hydrophobic compound from a supercooled oil-in-water emulsion. Ethyl octanoate (EO, 100 ppm) is added to a dispersion of crystalline or supercooled liquid eicosane droplets (10 wt%, d = 200 nm) stabilized with sodium caseinate (1 wt%) and incubated either with or without trypsin. In the absence of trypsin, the dispersions were stable and the headspace EO concentration in equilibrium with the liquid droplets is less than that in equilibrium with the solid droplets. In the presence of trypsin, the emulsions physically destabilize over 6 h as the caseinate is hydrolyzed and the supercooled liquid eicosane crystalizes initially rapidly but then more slowly. Incubation with trypsin does not affect the headspace EO concentration in equilibrium with solid droplets but for supercooled liquid droplets the headspace concentration increases from a low to a high plateau after 16 h incubation consistent with the droplets having crystalized. The equilibrium data are modeled in terms of the air–oil and air–caseinate solution partition coefficients of EO (9.0 × 10−5 and 4.6 × 10−3 respectively) assuming no interaction between crystalline fat and EO. This work shows that a digestive enzyme can trigger crystallization in an emulsion and be used to control the release of an entrapped hydrophobic compound.

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► Emulsions are widely used to delivery drugs, flavors and other chemicals.
► Emulsion droplets release hydrophobic solutes when they crystalize.
► Crystallization of supercooled droplets is induced by trypsin.
► Enzyme treatment can trigger controlled release of a hydrophobic solute.