The role of the drying method on fish oil entrapment in a fish muscle protein ̶ κ-carrageenan ̶ fish protein hydrolysate wall matrix and the properties of colloidal dispersions

Abstract

In an attempt to produce a dry functional ingredient from marine origin, salt-soluble fish muscle protein (MP), κ-carrageenan (C) and a fish protein hydrolysate (H) were used as wall material for fish oil (FO) microencapsulation, which was performed comparing two drying methods (spray-drying and heat-drying). Dry powders were initially obtained from MP and C separately and from the mixture of both (CMP), without and with addition of fish hydrolysate (MP-H, C–H, CMP-H). Finally, fish oil was entrapped in the most complex formulation (CMP-HFO). Composite powders with relatively low water solubility (≈50%) were obtained with both drying methods. The drying method strongly influenced the drying yield, as well as the rheological flow properties of the rehydrated dispersions. The mixture of fish muscle protein and/or fish hydrolysate with κ-carrageenan led to the formation of protein-polysaccharide interactions, deduced from the ζ potential, rheological properties, and submicron particle size analyses, which varied depending on the wall composition and drying method. Fish oil strongly interfered with such interactions, leading to highly heterogeneous microparticles and particle aggregates, which were much smaller when spray-dried than when heat-dried (D 4,3 = 8.13 ± 7.41 and 263.9 ± 15.08 μm, respectively). Fish oil remained highly entrapped by both methods (≥84%) and led to stable colloidal dispersions, the heat-dried sample presenting lower water resistance, noticeable higher viscosity and lower extent of lipid oxidation. Traces of residual heavy metals in the dry powders could be a limiting factor when using these marine-origin preparations as functional ingredients, depending on the quantities employed. • Stronger protein-carrageenan interactions in heat-dried samples. • Fish oil strongly interfered protein-carrageenan interactions in both dry powders. • Heat-dried CMP-HFO had lower water resistance and higher viscosity after dispersion. • Spray-drying induced higher lipid oxidation compared with heat-drying. • Trace amounts of heavy metals in both dry powders.