Fabrication of encapsulated oil powders from starch granule stabilized W/O/W Pickering emulsions by freeze-drying

The process stability of water-in-oil-in-water (W/O/W) double emulsions stabilized with food-grade OSA modified quinoa starch granules was investigated. The effect of oils with differing melting points, as well as the effect of in situ partial gelatinization of the granules, on stability of emulsions was also investigated. The physical stability and release of a tracer (carmine) from the internal aqueous phase of double emulsions were characterized after each process stage using particle size analysis, light microscopy and spectrophotometry. When liquid shea oil was used the particle sizes varied in mode of D[4,3] from 28 +/- 2 mu m for initial fresh double emulsions to 90 +/- 7 mu m for heat treated and 210 +/- 11 mu m for heat treated, freeze-dried and reconstituted emulsions. Non-heat treated emulsions collapsed on freeze-drying due to high susceptibility of liquid oil droplets towards destabilization, when the external aqueous phase is crystalized. When solid shea oil was used the mode of D[4,3] varied from 48 +/- 0 mu m in initial emulsions to 118 +/- 3 mu m for heat treated emulsions and the freeze-dried and reconstituted emulsions showed 62 +/- 3 mu m or 85 +/- 11 mu m for non-heat treated and heat treated samples respectively. Reconstituted freeze-dried emulsion retained the encapsulated marker to over 97%. Overall, application of oil phase solid at room temperature and in situ heat treatment had a positive impact on process stability towards freezing and freeze drying. The result of this study revealed the feasibility to develop food-grade oil filled powders from OSA modified starch Pickering emulsions with approximately 70 wt% oil content by freeze-drying. (C) 2015 Elsevier Ltd. All rights reserved.