Emulsifying properties of Ghanaian grewia gum

Grewia gums were extracted with phosphate (PB) and sodium metabisulphite buffers (SMB) and their emulsification properties in acidic oil-in-water emulsions on ageing were studied by means of droplet size distribution, zeta-potential measurements, interfacial composition analysis and viscometry. PB extracts showed smaller droplet sizes (similar to 10 mu m) than SMB isolates (>35 mu m) and greater long-term stability. PB-stabilised emulsions also demonstrated the least polysaccharide (similar to 0.6 mg m(-2)) and protein (similar to 0.2 mg m(-2)) interfacial coverage compared with SMB counterparts (similar to 1.5 mg m(-2) for polysaccharide and similar to 1 mg m(-2) for protein). zeta-Potential measurements revealed negative interfacial charge for all emulsions confirming the presence of polysaccharide-laden interfaces. Droplet size distribution also varied among emulsions during ageing indicating a complex relationship between interfacial composition and stability. The present work shows that different emulsifying properties may be obtained depending on the extraction technique employed that could be exploited in preparation of emulsions for flavour or bioactive-delivery applications.