Functional and antioxidant properties of whey protein hydrolysate/pectin complexes in emulsions and spray-dried microcapsules

• Enzymatic hydrolysis enhances antioxidant effect of the protein.
• Oxidative stability of encapsulated oil is improved by using β-LG hydrolysates.
• Electrostatic attachment of pectin to protein layers further inhibits lipid oxidation.
• Pectin increases thickness of the interfacial layer and immobilises prooxidants.

The aim of the present study was to investigate the potential of partially hydrolysed whey proteins to microencapsulate fish oil by spray-drying bilayer feed emulsions containing pectin, an oppositely charged biopolymer. Microcapsules were composed of fish oil, β-lactoglobulin (β-LG) or hydrolysates thereof produced by trypsin (DH6) and glucose syrup (DE38) as the matrix component. Pectin was attached to protein single-layer emulsions via electrostatic interactions using the layer-by-layer technique at pH 4.0. All emulsions exhibited good process stability during atomisation and drying as indicated by oil droplet size distribution and accordingly the microencapsulation efficiency was high (≥ 95.2 %) for all samples. The hydroperoxide formation in fish oil microcapsules prepared from single-layer feed emulsions was reduced in the presence of DH6 due to increased accessibility of antioxidant amino acids. The attachment of pectin to protein- or peptide-stabilised single-layer emulsions yielded bilayer microcapsules with increased stability (lower hydroperoxide content during storage). Increased thickness of the interfacial layer and the immobilisation of prooxidative ions by pectin may add to the antioxidative effect of the hydrolysate.