| Ulva fasciata is a kind of abundant green alga resources.Researches have investigated that polysaccharide extracted from Ulva fasciata has gelling and emulsifying activities.In this research Ulva fasciata polysaccharide?UFP?recognized as natural hydrophilic colloid was chosen to incorporate lipophlic functional compounds?essential oils which are volatile and not easily to emulsification and nutraceuticals with low solubility and crystallization?into emulsion system.The rheological properties of UFP solution and the physicochemical properties of emulsions prepared with UFP would be evaluated.Thereafter,the correlative relationship between various properties of emulsifiers and their influence on the characteristics of emulsions would be established.At first,the molecule and solution characteristics of UFP related to the emulsification properties were measured.The main constituent of Ulva fasciata were determined.It was suggested UFP existed in the form of sulfuric acid ester.The rheology of UFP solution has been investigated by steady shear and small amplitude oscillatory experiments.The effects of concentration,temperature,and time were systematically investigated.Steady-shear rheological measurement in a range of shear rate(1-1000s-1)exhibited that UFP has Newtonian behavior in diluted solutions?<0.5%,w/v?,pseudoplastic flow behavior at higher concentrations?>0.5%,w/v?.Speci?cally,UFP solution?4%,w/v?exhibited antithixotropic behavior.In small amplitude oscillatory experiments,both the storage modulus?G??and the loss modulus?G"?of UFP solution?1%,w/v?increased with frequency swept but G?increased more quickly.As a consequence,G?tends to overcome G”at 2.8 Hz.The research was carried out by choosing cinnamaldehyde as a model of essential oil to prepare emulsions stabilized by UFP.The mixtureofcinnamaldehydewithMCTbeforehigh-pressure homogenization was a useful method to inhibit the Ostwald ripening.Emulsion with particle size about 0.93?m were prepared by using UFP as emulsifier,with pressure at 75 MPa and 3 cycles.EmulsifyingpropertiesofUFPwereevaluatedin cinnamaldehyde/water emulsions in terms of droplet size distribution,rheological properties,visual phase separation,and zeta-potential.The cinnamaldehyde/water?10%,wt/wt?emulsions were formulated and stabilized by different concentrations of UFP?0.1-4%,wt/wt?.The obtained emulsions showed monomodal droplet size distributions with average droplet size?D[3,2]?below 1.0?m,when 1%?wt/wt?UFP was added as the emulsifying agent under a homogenization pressure of 75MPa.The rheological properties and zeta-potential of the emulsions appeared to be dependent on the UFP concentration.Furthermore,the UFP exhibited better emulsifying and stabilizing properties in the investigated system when compared to other commercial polysaccharides of gum Arabic and gum Ghatti.The results also suggested that the emulsifying and stabilizing mechanism of the UFP may not only be ascribed to its surface-active protein moiety,but also to the hydrophobicity of the polysaccharide itself.These findings provided a theoretical basis for potential utilization of UFP as a novel hydrocolloid emulsifying agent. |
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