Microencapsulation of salmon oil using fish gelatin/gum acacia complexes as wall materials for spray drying: Effect of gelatin source and processing on interfacial tension and oxidative stability

Fish gelatins (FG) are increasingly studied and implemented as substitutes for mammalian tissue-derived gelatins in microencapsulation owing to dietary, religious and health considerations. In this study, gelatin extracted from salmon skin (including two different hydrolysates), salmon bone and cod head were screened with respect to composition, molecular weight distribution and interfacial tension. Gelatins were used in combination with gum acacia (GA) and maltodextrin (FG:MD:GA = 1:2:1 and 2:1:1) for the microencapsulation of salmon oil via spray drying and the resulting oxidative stability of the oil was analysed. The effects of FG:GA ratio, oil to wall ratio and wall composition were investigated. All the fish gelatins and FG:GA combinations were found to lower interfacial tension and to form stable microcapsules after spray drying, with microencapsulation yields >85 % for all systems. The morphology of the microcapsules varied from mononuclear via multicore structures to grape-like aggregates depending on the source of the fish gelatin used and the FG:GA ratio. For example, microcapsules made using salmon bone gelatin showed a mononuclear morphology, compared to graping observed when using salmon skin gelatin under the same conditions. Overall, salmon bone and cod head gelatins were found to provide better protection against oxidation than the gelatins from salmon skin, both directly after spray drying and after storage for 6 months. For example, the peroxide values using salmon bone and cod head gelatin were 80 % and 71 %, respectively of the values obtained with salmon skin gelatin after 6 months storage. The differences in performance are discussed in terms of gelatin source, molecular weight and FG:GA interactions, with gelatin source having the most significant impact on oxidation. • Fish gelatin was derived from different species (cod and salmon) and parts of the fish. • Interfacial tension measurements reveal differences in film-forming ability of the gelatins. • Microencapsulation yields were >85 % for all systems studied. • Salmon bone and cod head gelatins outperform salmon skin gelatins in terms of oxidation. • Source of fish gelatin was found to have the most significant impact on oxidation over time.