Shear flow behaviour and emulsion-stabilizing effect of natural polysaccharide-protein gum in aqueous system and oil/water (O/W) emulsion

The main objective of the current work was to characterize the shear rheological flow behaviour and emulsifying properties of the natural biopolymer from durian seed. The present study revealed that the extraction condition significantly affected the physical and functional characteristics of the natural biopolymer from durian seed. The dynamic oscillatory test indicated that the biopolymer from durian seed showed more gel (or solid) like behaviour than the viscous (or liquid) like behaviour (G′ > G″) at a relatively high concentration (20%) in the fixed frequency (0.1 Hz). This might be explained by the fact that the gum coils disentangle at low frequencies during the long period of oscillation, thus resulting in more gel like behaviour than the viscous like behaviour. The average droplet size of oil in water (O/W) emulsions stabilized by durian seed gum significantly varied from 0.42 to 7.48 μm. The results indicated that O/W emulsions showed significant different stability after 4 months storage. This might be interpreted by the considerable effect of the extraction condition on the chemical and molecular structure of the biopolymer, thus affecting its emulsifying capacity. The biopolymer extracted by using low water to seed (W/S) ratio at the low temperature under the alkaline condition showed a relatively high emulsifying activity in O/W emulsion.

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► Durian seed gum exhibited the shear-thinning rheological behaviour.
► Durian seed gum showed more gel like behaviour rather than viscous behaviour (G′ > G″).
► Durian seed gums from different extraction conditions showed different emulsion stability.
► pH showed the most significant effect on the emulsifying activity of the biopolymer from durian eed.
► Emulsions containing durian seed gums from different conditions showed different droplet size.