High-internal-phase emulsions (HIPEs) for co-encapsulation of probiotics and curcumin: enhanced survivability and...

Synergistic biological activities of probiotics and curcumin can be achieved based on the gut-brain axis. However, it is still a challenge for utilizing both of them in actual food products due to their high sensitivity to environmental conditions. In the present study, high-internal-phase emulsions (HIPEs) were fabricated to co-encapsulate the probiotics and curcumin in response to the customer demand for convenience. β-Lactoglobulin-propylene glycol alginate composite hydrogel particles (β-lgPPs) with proper size and intermediate wettability were prepared at β-lg to PGA mass ratio of 2 : 1 and employed as particulate emulsifiers. Stable HIPEs with a fixed oil fraction (φ = 0.8) could be formed within a wide range of β-lgPPs concentrations, ranging from 0.1 to 2.0 wt%. Confocal laser scanning microscopy (CLSM) images indicated that the interfacial structure of the oil droplets was composed of both β-lg nanoparticles and a PGA network, which jointly contributed to the gel-like structures in HIPEs. An increase in elasticity and gel strength, as well as centrifugal stability, could be achieved by elevating the particle concentration as determined by diffusing wave spectroscopy and Lumisizer analysis. HIPEs with high particle concentrations showed a high resistance against pasteurization since no obvious flocculation or coalescence could be observed in these emulsions. HIPEs also provoked a significant reduction in the death of LGG as well as the chemical degradation of curcumin: up to 7.91 log CFU cm^-3 of LGG and 93.0% of curcumin were retained after pasteurization treatment. Moreover, the HIPEs could also retard the release of curcumin and protect the LGG in simulated gastrointestinal tract conditions. The results from this work provide useful information for developing a promising delivery system for the co-encapsulation of curcumin and probiotics.