Construction of a water-in-oil-in-water (W/O/W) double emulsion system based on oyster peptides and characterisation of freeze-dried products

In order to broaden the range of applications for oyster peptides in the food field, the amino acid composition of oyster peptide was analysed, after which the peptide sequence was identified using liquid-mass spectrometry technology. A W-1/O/W-2 double emulsion was prepared by the two-step shear emulsification method. The W-1/O/W-2 double emulsion was further freeze-dried after addition of alginate to obtain the final product, and the characteristics of the related product were analysed. The results show that oyster peptides are mainly composed of short peptides with molecular weights between 459.3 Da and 2716.3 Da. Polyglycerol polyrinoleate (PGPR) was selected as the emulsifier and added at 5% of the mass of the oil phase. The mass ratio of the oil phase to the water phase was O:W = 6:4, and optimal stability of the W-1/O emulsion was obtained by shearing and emulsifying for 2 min at 12 000 rpm. A superior W-1/O/W-2 double emulsion can be obtained by secondary emulsification in which the hydrophilic emulsifier Tween 80 was added at 0.8% (w/w) of the mass of the external water phase (W-2). The mass ratio of the emulsion to the external water phase was 5:5. The lyophilised product has good re-solubility, with the reconstituted emulsion maintaining the double-emulsion structure. Electronic nose results showed that the peculiar smell of the reconstituted emulsion was significantly lower than that of the oyster peptide solution. The results of this research provide a reference for the development and application of oyster peptides in the field of functional health foods.