The gel properties of sodium alginate (SA) have been revealed to be strongly correlated with its ratio of D-mannuronate to L-guluronate (M/G ratio). Herein, we focused on SA with different M/G ratios to conduct an in-depth study on the effect of the M/G ratio difference on physicochemical stability and calcium release behavior of the Pickering emulsion stabilized by calcium carbonate (CaCO3). The oil phase was added to the aqueous phase, prepared by SA with different M/G ratios (2.23, 0.89, and 0.56) and CaCO3, for one-step shearing to obtain the E1, E2, and E3 emulsions, respectively. The results of the particle size, microstructure, long-term stability, rheological, and microrheological properties of the emulsions showed that the E3 emulsion, prepared by SA with a smaller M/G ratio, had a smaller particle size and has remained in a flow condition during the long-term storage, while the E1 and E2 emulsions had a gelation behavior and a stronger viscoelasticity. Moreover, the emulsion, as a liquid calcium supplement, is not only convenient for oral intake while meeting the calcium needs of the body, but also controls the release of Ca2+. The calcium release of the emulsions in a simulated gastric environment demonstrated that the calcium release ratio increased with the decrease of SA concentration, with the increase of M/G ratio, and with the decrease of oil phase volume.
Our lab’s studies have found that heavy calcium carbonate (CaCO3) with sodium alginate (SA) can synergistically stabilize Pickering emulsion. However, there were significant differences in the flow characteristics of the emulsions obtained by different preparation methods during storage. Herein, in this current work, Pickering emulsions were prepared by two-step emulsifying method (SA was added into the primary emulsion stabilized by CaCO3 for secondary shearing, M1) and one-step emulsifying method (oil phase was added to homogeneous dispersed CaCO3-SA solution for one-step shearing, M2), respectively. The particle size, microstructure, rheology and microrheological properties of these two kinds of emulsions and the interaction of CaCO3 with SA were analyzed. The results showed that the droplet size of M1 emulsion was 21.78–49.62 μm, and that of M2 emulsion was 6.50–11.87 μm. M1 emulsion had stronger viscoelasticity, and could transform into a gel state during storage. However, M2 emulsion remained in flow condition all the time which was related to the interaction between SA and CaCO3 in the aqueous phase.
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