Sodium caseinate–maltodextrin conjugate stabilized double emulsions: Encapsulation and stability

The potential food applications of water-in-oil-in-water (W₁/O/W₂) double emulsions are great, including the encapsulation of flavours or active ingredients. However, the stability of these emulsions restricts their applications in food systems. Sodium caseinate (NaCN)–maltodextrin (Md40 or Md100) conjugates were investigated for their potential to improve the stability of W₁/O/W₂ double emulsions compared to NaCN. NaCN–Md40 and NaCN–Md100 conjugates were prepared by a Maillard-type reaction by dry heat treatment of mixtures of NaCN–Md40 or NaCN–Md100 at 60 °C and 79% relative humidity for 4 days. Water-in-oil-in-water (W₁/O/W₂) double emulsions with NaCN, NaCN–Md40 or NaCN–Md100 as outer aqueous phase containing emulsifier were prepared using a two-step emulsification process. General emulsion stability was characterised by determining the droplet size distribution, viscosity characteristics and by confocal microscopy of the W₁/O/W₂ double emulsions on formation and after their storage under accelerated shelf life testing conditions at 45 °C for up to 7 days. Inner phase encapsulation and stability were characterised by monitoring the level of entrapped Vitamin B₁₂ in the inner aqueous phase on formation of the double emulsions and after storage at 45 °C for up to 7 days. Conjugate stabilized emulsions were more generally stable than NaCN stabilized emulsions. In comparison to NaCN stabilized emulsions, conjugate stabilized emulsions showed improved Vitamin B₁₂ encapsulation efficiency in the inner aqueous phase on emulsion formation and improved encapsulation stability following storage of the emulsions.