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

The potential food applications of water-in-oil-in-water(WI/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 W-1/O/W-2 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 degrees C and 79% relative humidity for 4 days. Water-in-oil-in-water (W-1/O/W-2) 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 W-1/O/W-2 double emulsions on formation and after their storage under accelerated shelf life testing conditions at 45 degrees C for up to 7 days. Inner phase encapsulation and stability were characterised by monitoring the level of entrapped Vitamin B-12 in the inner aqueous phase on formation of the double emulsions and after storage at 45 degrees 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 B-12 encapsulation efficiency in the inner aqueous phase on emulsion formation and improved encapsulation stability following storage of the emulsions. (C) 2009 Elsevier Ltd. All rights reserved.