Oral behaviour of emulsions stabilized by mixed monolayer

Controlled flavour release is highly important for the formulation of food emulsions. However, manipulating oral behavior and maintaining the stability of the flavoured emulsion is quite challenging. Hence, this study aims to investigate the effect of emulsion stability and oral behaviour using mixed emulsifier monolayers of different nature for their controlled flavour release. Orange oil flavoured (0.1% orange oil +10% sunflower oil) oil-in-water emulsions were prepared by microfluidization through modified starch (MS) and whey protein isolate (WPI) with different mass ratios (0.5:0.5, 0.5:1, 1:0.5, 1:1, 1:0 and 0:1) of emulsifiers. The fabricated emulsions were <0.13 μm in size (d₃₂) with stable oil droplets having strong negative charges. The 0.5:0.5 and 0:1 emulsion were depicted an increase in size d₃₂ (1.17 and 0.93 μm) and unstable during storage at 28 ± 1 °C than the emulsions stored at 4 ± 0.1 °C. All the emulsions were exhibited Newtonian flow; however once mixed with artificial saliva, the 1:0 emulsion showed shear thinning behaviour. During oral processing, in-vitro and in-vivo exhibited flocculation and coalescence; subsequently, structural deformation was observed with an increase in size (d₃₂) and weak negative charge in 1:0.5 and 1:0 emulsions. Backscattering profile revealed more destabilization for 1:0 and less for 1:0.5 emulsions. Contrarily, other emulsions did not show any changes. Therefore, oral processing of emulsions results suggested that 1:0 had quick destabilization and 1:0.5 changed gradually. Thus, mixed emulsifier monolayer contributed significantly to the behavior of emulsions when interacting with saliva and it can be useful for controlled flavour release.