Utilization of polysaccharide coatings to improve freeze-thaw and freeze-dry stability of protein-coated lipid droplets

The impact of freezing-thawing and freeze-drying on the physical stability of oil-in-water (O/W) emulsions containing protein-coated and protein/polysaccharide-coated droplets has been studied. O/W emulsions (2 wt% corn oil, 0.12 wt% P-lactoglobulin, pH 3.5) were prepared that contained either 0 or 0.2 wt% pectin or iota-carrageenan, and 0-8 wt% maltodextrin. The emulsions were then subjected to either freeze-thaw cycling (-20 degrees C, 22 h; +30 degrees C, 2 h; x2) or freeze-drying and reconstitution (pH 3.5). The stability of the emulsions to freeze-thaw or freeze-dry processing was then analyzed using particle size, microstructure, and creaming stability measurements. All emulsions were unstable to these processes in the absence of maltodextrin, which was attributed to extensive droplet aggregation during freezing and/or dehydration. In the presence of maltodextrin, the emulsions containing polysaccharide coatings had better stability to droplet aggregation after freeze-thaw cycling and freeze-drying than emulsions containing no polysaccharides. Specifically, considerably less maltodextrin was required to form stable emulsions when the polysaccharide coatings were present. We propose that the anionic polysaccharides formed a protective layer around the lipid droplets that improved their stability to freeze-thaw cycling and freeze-drying. (C) 2007 Elsevier Ltd. All rights reserved.