Abstract
In order to impart emulsifying ability to gel-forming polysaccharides that have not been used as emulsifying agents, three kinds of polysaccharides, agar, curdlan, and gellan gum were converted to microgels by different gelation methods via the bottom-up and top-down approaches. We clearly demonstrated that agar and curdlan acquired the ability to emulsify an edible oil by microgel formation. Among the colloidal properties of microgel suspensions such as microstructure, particle size, zeta-potential, viscosity, and surface hydrophobicity, we pointed out the importance of particle size on the emulsifying ability of polysaccharide-based microgels. The creaming behavior of the microgel-stabilized emulsions depended on the polysaccharide types and microgel preparation methods. The emulsion stability against oil droplet coalescence was extremely high for agar and curdlan microgel-stabilized emulsions during storage in the static condition, whereas different stability was observed for both the emulsions, that is, the curdlan microgel-based ones were more resistant to dynamic forcible destabilization by centrifugation than the agar ones, which can be attributed to the surface hydrophobicity of the microgels.
Highlights
Many food products such as dressings, coffee creams, and white sauces exist as an oil-in-water (O/W) emulsion where small oil droplets are dispersed in an aqueous continuous phase.[1]
Many kinds of polysaccharides play a major role in stabilizing the interface between oil and water in combination with proteins, they are not usually used for food emulsions as a sole emulsifying agent because typical hydrophilic polysaccharide molecules are surface inactive in principle unless they include protein moieties responsible for emulsifying ability like gum arabic and soluble soybean polysaccharide (SSPS) for emulsions designed as flavor products.[1,12,18,19,20]
We investigated effects of microgelation on emulsifying ability of agar, curdlan, and gellan gum that have been scarcely utilized as stand-alone emulsifying agents
Summary
Many food products such as dressings, coffee creams, and white sauces exist as an oil-in-water (O/W) emulsion where small oil droplets are dispersed in an aqueous continuous phase.[1]. The emulsifying agents applied to formation of the system are at the same time required to delay progress of these phenomena once oil and water are emulsified. Whereas smallmolecule emulsifiers adsorb to the oil–water interface to efficiently stabilize the system to oil droplet coalescence throughout the Gibbs–Marangoni effects,[1,11] macromolecules like proteins form elastic layers on the oil droplet surfaces during emulsification processes to provide the effective steric and electrostatic effects responsible for stability against coalescence.[1,12] Despite these favorable properties of proteins to stabilize emulsions, the adsorbed proteins are intrinsically highly susceptible to pH value change, salt addition, and processing such as heat and freeze-thaw treatments,[1,13] and they are often covered with oppositely charged polysaccharides such as pectin, soluble soybean polysaccharide (SSPS), and carrageenan.[14,15,16,17] many kinds of polysaccharides play a major role in stabilizing the interface between oil and water in combination with proteins, they are not usually used for food emulsions as a sole emulsifying agent because typical hydrophilic polysaccharide molecules are surface inactive in principle unless they include protein moieties responsible for emulsifying ability like gum arabic and SSPS for emulsions designed as flavor products.[1,12,18,19,20]
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