| Food-grade Pickering emulsions stabilized by edible solid particles have attracted more and more attentions due to their wide potential applications in food,pharmaceutical and other industries.However,it has been found that food-grade particles are mainly used to stabilize oil-in-water emulsions,while food-grade particles for stabilizing water-in-oil emulsions are extremely inadequate.Phytosterols are known as natural substances with cholesterol-lowering bioactivity,and their water insolubility and low oil solubility make phytosterols great application potential in stabilizing water-in-oil Pickering emulsions.Therefore,in the present work,phytosterol particles for stabilizing water-in-oil Pickering emulsions were fabricated using anti-solvent precipitation method,and the structure-function relationship was investigated.Besides,the potential applications of phytosterol-based Pickering emulsions in food industry were also studied.The main results are as follows:(1)The water-dispersed phytosterol(PS)particles were fabricated through simple anti-solvent precipitation method and then characterized.Compared with native phytosterols,those treated by anti-solvent precipitation could be well dispersed in water phase.SEM results showed that the microstructure of PS particles was disc-like morphology,compared to the sheet-like native phytosterols.Besides,both the particle size and aspect ratio were significantly decreased.The water-dispersed PS also showed reduced crystallinity.The contact angle decreased with decreasing organic/aqueous-phase ratio,but all larger than 90 deg,which indicated that they had great potential for stabilizing water-in-oil emulsions.(2)The ability of PS particles(dispersed in water phase)stabilizing emulsions was investigated.Water-in-oil(W/O)Pickering emulsions were successfully fabricated by water-dispersible phytosterol(PS)particles formed through simple antisolvent precipitation.The emulsion type was demonstrated as W/O type by droplet test and confocal laser scanning microscopy.The properties of W/O emulsions were significantly influenced by changing the water-phase fractions or particle concentrations.No emulsion was formed at a PS particle concentration lower than phytosterol solubility in oil.When particle concentration of PS exceeded its oil solubility,PS particles probably acted as a stabilizer involved in emulsification.The droplet size decreased with the increase of particle concentration,and then reached a plateau.Besides,W/O emulsions with up to 80% water fraction could be stabilized by 1% PS particles in the aqueous phase.(3)The ability of PS particles(dispersed in oil phase)stabilizing emulsions was also investigated.Results showed that antisolvent pretreatment of phytosterols in ethanol/water system facilitated the dispersion of disc-like phytosterol particles in oil phase and transformation into microcrystals.Water-in-oil Pickering emulsions with droplet sizes of 80 μm-100 μm could be fabricated at phytosterol concentrations of 1.5%-3.0% w/v in oil and water phase fractions of0.2-0.6.The phytosterol molecules dissolved in oil phase contributed to emulsion stabilization through interfacial crystallization during emulsification,evidenced by polar microscopic observation.Synergistic stabilization of oil-water interface both by pre-existed PS crystal particles and instantaneously formed by dissolved PS molecules at the interface were found.Besides,emulsions stabilized by microcrystalline phytosterols showed higher freeze-thaw stability than that of polyglycerol polyricinoleate(PGPR)emulsions.(4)The microcrystalline phytosterols stabilized water-in-oil emulsions were applied as encapsulation system for Na Cl,and the release profile was investigated.Compared to PGPR emulsion,phytosterols stabilized emulsion was more stable against osmotic pressure.Moreover,with the increase of particle concentration,the release of Na Cl was decreased.Besides,the salt release from phytosterols stabilized Pickering emulsions showed a temperature-dependent profile which could have potential application in controlled-release system.(5)The ability of microcrystalline phytosterols stabilized water-in-oil emulsions applied as solid fat substitute in biscuits was preliminary investigated.The results showed that the hardness of biscuits both in emulsion group and shortening group had no significant change.The color of the biscuits turned paler with the increase of the emulsion substitute ratio.Moreover,compared to the control group via fluorescence detection,the level of fluorescent advanced glycation end products(AGEs)and protein oxidations in biscuits was decreased probably owing to the antiglycation of phytosterols,introduction of unsaturated fatty acids and reduction in total fat content. |
PDF Full Text Request