| As a kind of vegetable oil squeezed from coconLit pulp,coconut oil(CO)has been widely used in food,chemistry industry and other fields for its antibacterial,anti-oxidant and anti-viral properties.Generally,CO is used to being emulsified for utilization but the stability of the emulsion is a key technical problem need to be solved yet.To inhibit the aggregation of small droplets in oil-in-water(O/W)emulsions,polysaccharides have been utilized to stabilize emulsions depend on some properties in terms of formation of gel-like network structure in water or modification into amphiphilic molecules.In this study,we used water soluble polysaccharides as emulsifiers or stabilizers to prepare O/W coconut oil emulsions assisting by ultrasonic treatments.Following this,the lutein was loaded into the oil phase of emulsions and the properties of the emulsions were investigated.The aim of this study is to expand the application of polysaccharides for preparing O/W emulsions and the utilization of lutein in emulsion systems for medicine and food industry.The main findings and conclusions of the research are as follows:(1)Properties of polysaccharidesBy means of dissolving different polysaccharides including methylcelluIose(MCC),propylene glycol alginate(PGA),xanthan gum(XG)and PGA-XG complex to prepare polysaccharide solutions as water phase,interfacial tensions between CO and water phase were determined and compared each other.It was found that the ability of polysaccharides to reduce the interfacial tensions remained some differences.MCC,PGA and PGA-XG complexes apparently reduced the interfacial tension between oil and water phase.Among these polysaccharides,PGA-XG complex showed the highest decrease to interfacial tension while XG appcared to not able to reduce the interfacial tension.In addition,at the same percent concentration(w/w),PGA-XG complex solution showed the highest apparent viscosity.Furthermore,the results of isothermal differential titration experiments suggested that PGA and XG might be bound each other to present interactions in solutions.Therefore,we decided to use PGA-XG as an emulsifier to stabilize the W/O CO emulsions.(2)Properties of polysaccharides treated by ultrasonic treatmentsThe effect of the ultrasonic treatments on the polysaccharide solutions was investigated.The results showed that the ultrasonic treatments was able to significantly lower the apparent viscosity of polysaccharide solutions.It was also found the apparent viscosity of polysaccharide solutions by ultrasonic treatments could be reduced more quickly in the initial stage than in the later stage.The determination of molecular weight suggested that ultrasonic treatments could narrow the molecular weight distribution of polysaccharides which indicated polysaccharide degradation,and the deeper degradation occurred by the ultrasonic treatment of 390w power compared to 270w power.Through stability investigations,it was found that 270w ultrasonic treatment for 7 min led to the best emulsifying stability for preparing emulsions.(3)The stability of emulsion prepared with PGA-XG complexUsing a series of mass ratio of PGA/XG(3:7?4:6?5:5?6:4?7:3)as emulsifiers to stabilize O/W emulsions,5%(w/w)CO content emulsions were prepared by 270w ultrasonic treatment for 7min.To study the stability of emulsions,the average particle size and particle size distribution of emulsions were measured.In addition,the oil droplets in the emulsions were observed by microscope,and the stability of the emulsion was analyzed by means of stability analyzer,and the zeta-potential of the emulsions was determined.The results showed that the emulsions with PGA/XG of mass ratio of 3:7 or 4:6 presented the best stability which characterized the smallest particle size and narrow particle size distribution.According to determination of stability analyzer,the emulsions prepared with polysaccharide complexes indicated better stability and smaller instability coefficient than using the single polysaccharide for preparing emulsions.(4)Comparative study on ultrasonic and high pressure homogenization process for preparing emu sionsUsing polysaccharide complex as emulsifier for emulsion stability,emulsions were respectively prepared at 30 C by processes of 7 min ultrasonic treatment and high pressure homogenization of 30 MPa and 50 MPa.To compare the stability of emulsions by two processes,EAI and ESI of emulsions were measured.The results showed that both processes could reduce the apparent viscosity of the polysaccharide complexes while the emulsion prepared by ultrasonic treatments possessed better stability than high pressure homogenization owing to its smaller average particle size.The ultrasonic treatment for emulsions obtained higher EAI and ESI than high pressure homogenization treatment,which indicated that helped the polysaccharide complexes to play more effective emulsifier roles.(5)Study on liposoluble lutein loaded by CO emulsionsBased on a good stability of CO emulsions prepared with PGA-XG complex,liposoluble lutein was dissolved in oil phase of emulsions and then the and anti-oxidation characteristics of emulsions during storage were determined.The results showed that the emulsions loaded lutein could keep apparent stability for less particle size changes.According to ABTS free radical scavenging and iron ion reduction experiments,the lutein loaded in emulsions were proved to have a good antioxidant ability.Thus,the advantages of O/W emulsions provided potential application values for loading lutein. |
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