Characterization of a casein-sodium alginate emulsion gel

Stable emulsion gels based on micellar casein (MC) and sodium alginate (SA) have been achieved by one-pot homogenization. Sodium caseinate (SC) has a similar protein composition but different conformation to MC. It is unclear whether SC is a viable alternative to MC for fabrication of emulsion gels, or whether the preparation method affects the characteristics of the gel. This study aimed to explore the effect of one-step, or two-step homogenization on the properties of emulsion gels stabilized by MC or SC at oil volume fraction of 0.65–0.80 (mL/mL), combined with SA. The stability, moisture distribution, rheological properties and 3D printing characteristics of the emulsion gels were determined. Light microscopy showed that the oil droplet size was influenced by the preparation method and decreased with increasing oil content, more so after the one-step homogenization. The emulsion gels had excellent storage stability and no phase separation was seen after storage for 230 days; they also had high pH- and heat-stability, regardless of fabrication method. SC-SA emulsion gels contained more immobilized water than MC-SA gels, but the free water was mostly removed by centrifugation. The storage and loss moduli (G′ and G″) of the gels increased markedly after centrifugation; the resulting, more concentrated gels had better self-supporting properties. The emulsion gels were highly resistant to simulated gastric digestion, but were almost completely disrupted after simulated intestinal digestion. Emulsion gels based on MC/SC-SA appear to have great potential for use in 3D food printing. • Micellar casein (MC)-emulsion gel need lower oil phase than sodium caseinate (SC). • MC-sodium alginate (SA) emulsion gels had lower G′ and G″ values than SC-SA gels. • SC-SA emulsion gel contained more immobilized water than MC-SA gels. • Emulsion gels were resistant to degradation during simulated gastric digestion. • Concentrated emulsion gels had good self-supporting properties for 3D printing.