Fabrication Of Food-grade Pickering Emulsions Stabilized By Cyclodextrins

The development of food grade Pickering emulsion is a new research field in the food industry.Pickering high internal phase emulsion is an important part of Pickering emulsion,which has potential application as the solid fat substitute and food nutrient carrier.The search for edible particle stabilizers has always been a hot topic in the research of food-grade Pickering emulsions.Cyclodextrin（CD）has the ability to construct Pickering emulsions,but there are few related studies.In this study,cyclodextrin was taken as the main research object,and the effects of CD structure,CD concentration,oil phase properties and oil phase volume fraction on the formation and stability of O/W Pickering emulsions were studied systematically.Then,the O/W Pickering high internal phase emulsions（HIPEs）stabilzed byβ-CD particles,were successfully constructed for the first time,and the microstructure,mechanical properties and stability of HIPEs were analyzed.The results of this study can not only enrich the theory of Pickering emulsion,but also promote the green and efficient preparation of new food grade Pickering HIPEs.The main research contents and relevant conclusions of this paper are as follows:（1）The effects of CD structure,CD addition amount,oil phase and oil phase volume fraction on the formation of oil-in-water（O/W）Pickering emulsions were investigated.The microstructures,microrheological properties and stabilities of medium-chain triglyceride（MCT）-based Pickering emulsions stabilized byα-,β-andγ-CD were systemically compared.In order to clarify the difference of CDs in emulsifying capacity,the formation of CD/MCT inclusion complexes were simulated using molecular docking.It was found that bothα-andβ-CD exhibited the good emulsifying stabilities,which could be further enhanced with the increasing oil phase volume fraction and CD addition amount.The obvious effect of oil phase could be also observed.Bothα-andβ-CD could reduce the O/W interfacial tension with the similar performance.For its stronger interaction with MCT,α-CD was easier to form the supramolecule with MCT,which led to its higher emulsifying stability than that ofβ-CD at low addition amount（0.5%）.Althoughβ-CD had the lower adsorbing capacity at O/W interface thanα-CD,it could not only play the emulsifying role at the interface but also prevent the collision and coalescence of oil droplets through its precipitation aggregation in the aqueous phase,which contributed to its stronger performance at high addition amount（1.5%and 2.5%）.（2）The application ofβ-CD as a particle stabilizer for Pickering HIPEs with sunflower seed oil as dispersed phase was studied.It was found that the oil-in-water（O/W）Pickering HIPEs could be fabricated at the oil phase volume fraction（φ）of 75%（v/v）andβ-CD concentration（c）of 0.5-2.5%（w/v）.The microstructure observation of HIPEs indicated thatβ-CD not only played the emulsifying role on the oil-water interface,but also prevented the coalescence of oil droplets of HIPEs through its 3D network in aqueous phase.With the increasingβ-CD concentration,the oil droplet size of HIPEs declined while their mechanical properties gradually strengthened,which coincided with their centrifugation stabilities.The light stability of lutein against UV irradiation could be enhanced by encapsulation into these HIPEs,and the protective effects of HIPEs were close at all testβ-CD concentrations.（3）The feasibility of food-grade Pickering HIPEs stabilized by a mixture ofβ-CD and sugar beet pectin（SBP）was evaluated.The factors affecting the microstructures,mechanical properties,and stabilities of the Pickering HIPEs were systematically investigated.The corresponding hybrid particles were also separated and characterized to reveal the formation mechanism.The results indicated that the mixture could induce the formation of HIPEs with an oil phase volume fraction（φ）of 75%using a one-step high-speed shearing process at room temperature.The composition(the mass ratio ofβ-CD to SBP,R_c/s)and concentration（W）of the mixture had significant effects on the formation and properties of HIPEs.When W≥1.0%and Rc/s=2:2 or 3:1,HIPEs had smaller oil droplets,higher gel strengths,better centrifugation stabilities and lutein protection effects.The spectral analysis suggested that SBP could adhere to the surface ofβ-CD particles to form hybrid particles during the homogenization.Compared with nativeβ-CD particles,these hybrid particles had higherζ-potential absolute values,and the SBP could also increase the viscosity of the aqueous phase,which contributed to the formation and properties of these HIPEs.