| Pickering Emulsion is stabilized by one or more kinds of colloid particles instead of low-molecular-weight surfactants or surface-active polymers.Pickering emulsions present greater advantages than traditional emulsion,due to their high stability.Cellulose is the most abundant carbohydrate polymer resource produced in the biosphere available.Nano-cellulose,a key materials based on cellulose are highly promising as stabilizers for Pickering emulsion in food,cosmetics and pharmaceutical industries on account of their sustainability,biodegradability,and nontoxicity.Several characteristics of the cellulose nano-particles have been reported to play an important role in the properties of the emulsions stabilized by particle,such as source,morphology,surface chemistry and particle concentration.In this work,nano-cellulose with different crystalline allomorph or aspect ratios were investigated as stabilizers for oil-water Pickering emulsion.Furthermore,corn oil Pickering emulsions were prepared and investigated their properties in vitro gastrointestinal digestibility.Finally,ASA Pickering emulsions were prepared by lonely nano-cellulose and their properties were studied.These work may be contribute to stabilization mechanisms of non-spherical particle as stabilizers for Pickering emulsion and providing theoretical guidance for practical production.These work may expanded the potential application of its stable emulsion in various industries.(1)The effect of nano-cellulose crystalline allomorph on properties of Pickering emulsions have been studied.At first,CNCs-I and CNCs-II with various crystalline allomorph were prepared and chartered and then Pickering emulsions stabilized by them were prepared and chartered.The emulsion ratios of Pickering emulsions stabilized by CNCs-I were higher than that by CNCs-II.Pickering emulsions stabilized by CNCs-I presented about two times smaller droplets size and were more stable after centrifugation than CNCs-II.Thus,CNCs-I presented a superior ability to stabilize O/W interface of Pickering emulsion compared to CNCs-II.Different crystalline allomorph resulted in the difference of hydrophilicity of CNCs,consequently affected their ability to stabilize O/W Pickering emulsions.This point was supported by analysis of crystalline structure of nano-cellulose,which showed that hydrophilicity of CNCs-I was weaker than that of CNCs-II,and the contact angle and surface energy of the self-standing CNCs films studies also supported this point.(2)The effect of nano-cellulose aspect ratios on properties of Pickering emulsions have been studied.At first,CNCs and CNFs with different aspect ratios were prepared and chartered and then Pickering emulsions stabilized by them were also prepared and chartered.The emulsions stabilized by CNCs showed smaller emulsion droplets diameter than stabilized by CNFs,but showed worse stability after storage long time.Furthermore,they showed the similar emulsion volume ratios at the same dosage of CNCs and CNFs.Furthermore,the effect of salt concentration on the emulsion stability was studied,In present of salt in the system,Pickering emulsions stabilized by CNFs showed smaller emulsion droplets diameters、higher emulsions volume ratios and better stability,which shows that CNFs presented the better ability to stabilized Pickering emulsions.This may be attributed to the conversion of emulsions to gels occur at a salt concentration of 50 mmol/L and higher.These difference may be mostly resulted from distribution of nano-cellulose at the interface of oil and water.CNFs could be connected emulsion droplets,forming a loose network.This loose network may lead to steric hindrance,responsible for the good performance of CNFs as Pickering emulsion stabilizers especially in the present of salt.(3)To investigate how the aspect ratios of nano-cellulose affects corn oil in vitro digestibility,corn oil in water Pickering emulsions were prepared and characterized.At first,CNCs-I、CNCs-II and CNFs were prepared,which be with aspect ratios of 18、4 and 90(at least)respectively.The variation of particle size in terms of D[4,3],Zeta potential,and microstructure during the gastrointestinal digestion and the free fatty acid(FFA)released in small intestine phase were investigated.The results showed that no significant increase in D[4,3] after oral digestion.After gastric digestion,D[4,3] became larger notably for all emulsions,but have no notably difference between the three emulsions.After gastric digestion,D[4,3] also became larger notably for all emulsions,but also have no significant difference between the three emulsions.During digestion process,the trends of Zeta potential of the three emulsions were similar.After oral digestion,the values of Zeta potential became larger,however became smallest after all emulsions,while there was no notably difference between the three emulsions.After intestinal digestion,all emulsion droplets flocculate and formed flocs with larger size.And the contents of FFA released decreased in the order of emulsions stabilized by CNCs-I、CNCs-II and CNFs.But,both D [4,3] and value of Zeta potential showed no notably difference between the three emulsions.Therefore,there was no obvious relationship between FFA release and D [4,3] or value of Zeta potential.Different distribution of nano-cellulose at the interface of oil and water may be the key factor for FFA release.(4)ASA Pickering emulsions were prepared by alone CNCs or CNFs and characterized in terms of Zeta potential,emulsion droplets diameters(D[4,3]),emulsions volume ratios and rheological behaviors.The results showed that with the increasing of dosage of nano-cellulose,the value of Zeta potential and emulsions volume ratios increased,and D[4,3] reduced.Furthermore,the Pickering emulsions stabilized by CNFs showed higher Zeta potential,smaller D[4,3] and better stability than the emulsions stabilized CNCs.The analysis of rheological behaviors showed that the viscosity of emulsions stabilized by CNFs were high,and the Pickering Emulsion stabilized by CNFs at 2% concentration tended to form gel,which is benefit to form stable ASA Pickering emulsions. |
