| Emulsion,as one of the widely used forms in the food industry,plays significant roles in improving food flavour,forming special texture and delivering nutrients.Compared with traditional emulsions that are stabilized by chemical surfactants,Pickering emulsion has shown the advantages of strong stability,safety and easy preparation.The construction of Pickering particles(solid particles)is vital for the preparation of Pickering emulsion.As a natural bioactive polysaccharide,chitosan has excellent characteristics such as low price,wide sources,and easy modification.However,there are some drawbacks when chitosan is solely used as Pickering stabilizers.In this study,an ion gel method was used to prepare chitosan-sodium tripolyphosphate-tea polyphenol(CS-TPP-GTP)composite particles.The particle size distribution,Fourier infrared spectroscopy(FTIR),scanning electron microscope(SEM),and three-phase contact angle and other indicators was determined.Afterwards,a O/W type Pickering emulsion was prepared using the CS-TPP-GTP particles.Effects of different preparation conditions on the particle size and stability of the emulsion were investigated.Finally,the emulsion system was used to load quercetin,and its effect on the storage stability and digestion stability of quercetin was studied.These results may contribute to broadening the application of chitosan as Pickering particles and improving the stability of quercetin.The main contents and results are summarized as follows:(1)Construction and characterization of chitosan-sodium tripolyphosphate-tea polyphenol composite particles(CS-TPP-GTP).CS-TPP-GTP particles were prepared by electrostatic adsorption,and the composite particles were characterized by measuring FTIR,three-phase contact angle,particle size distribution,SEM and PDI values and other indicators.FTIR showed that tea polyphenols were successfully bound to CS-TPP particles.The addition of tea polyphenols improved the hydrophobicity of CS-TPP composite particles,making the three-phase contact angle closer to 90°.The results of particle size analysis show that the particles are uniformly distributed within the range of 1140 nm to 1810 nm.(2)The effect of preparation conditions on the stability of the CS-TPP-GTP-stabilized emulsion.The influence of different preparation conditions(i.e.,pH value,particle addition,salt ion concentration and oil phase fraction)on the stability of the emulsion(storage stability,centrifugal stability,thermal stability),droplet morphology and emulsification index were studied.Also,the rheological properties of the emulsion were analysed.It is found that the emulsion can exist stably in a low-pH environment,a high-salt ion concentration(0.2 mol/L),and a low particle concentration(0.25%).With the oil phase fraction increases,the performance of the emulsion increases.When the oil phase fraction reached 70%,the emulsification index approaches 100%,and most emulsions can be stored stably for 30 days.The emulsion has good centrifugal stability and thermal stability against pasteurization treatment.Rheological experiments show that when the oil phase fraction reached 70%,the emulsion is pseudoplastic fluids with solid gel characteristics.(3)Application of CS-TPP-GTP-stabilized emulsion for loading quercetin.The CS-TPP-GTP-stabilized emulsion was used to load quercetin.The appearance,microstructure,dynamic oscillation and steady-state rheological properties of the emulsion before and after loading were studied.The treatment with quercetin directly dissolved in the oil phase served as a control.Effects of the emulsion on the storage stability and digestion stability of quercetin were analysed.The results showed that after 15-day storage,the retention rate of quercetin in the emulsion group was as high as 58.23%,while it was only 12.86% in the control.In addition,the emulsion can also significantly improve the digestive stability of quercetin. |
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