In-vitro oral digestion of microfluidically produced monodispersed W/O/W food emulsions loaded with concentrated sucrose solution designed to enhance sweetness perception

Monodispersed W1/O/W2 emulsions consisting of sunflower oil droplets containing a single large internal droplet or numerous small internal droplets of concentrated sucrose solution were prepared by microfluidic emulsification. The external droplet interface was stabilized by waxy rice starch, which hydrolyzes during oral processing thereby releasing the encapsulated sucrose solution to the proximity of taste receptors imparting a higher sweetness perception compared to adding the same amount of sugar to the bulk phase. The sucrose release was tracked by adding NaCl to the internal phase as a conductivity tracer. Core/shell droplets containing 50 wt% sucrose and 1.5 wt% NaCl in the internal phase, 1.40–2.86 wt% polyglycerol polyricinoleate (PGPR) in the middle phase, and 4 wt% gelatinized waxy rice starch in the external phase were produced with 100% encapsulation efficiency and showed stability against coalescence for at least two months, because the gelatinized starch acted as a highly efficient Pickering stabilizer. The sucrose release from the inner droplets during in-vitro oral processing at 37 °C for 30 s with 50 U/mL α-amylase increased from 16% to 49% when the PGPR concentration in the oil phase was reduced from 2.86 wt% to 0.7 wt%. Core/shell droplets were less stable during storage when the surface-active molecularly dissolved octenyl succinic anhydride (OSA) modified starch was selected as stabilizer although the oil droplets were smaller due to the lower interfacial tension at the external interface. W1/O/W2 emulsion consisting of numerous internal droplets coalesced during storage in one day and released 91% of sucrose during in-vitro oral processing.