###### Abstract
As mentioned above, amphoteric chitosan was prepared to replace sodium acrylates copolymer as an emulsifier for the preparation of emulsions to increase the properties of moisturizing, antibacterial activity and stability. Emulsion stability can be determined according to the method of CIPAC MT 36.3. For instance, the water of different hardness was considered to examine emulsion stability [20]. The result showed that the emulsifiability capacity could be affected when emulsifiable concentrates are exposed to high temperatures. Extended from this method and according to WHO's standard, the emulsion is diluted 20 times and stood for 1 h. The hygienic standards are met when no oil floats on the top and no water sinks at the bottom. The chitosan has been used as a copolymer, a surfactant, an additive, or an emulsifier by some studies to examine the stability of emulsions. For example, chitosan was used as a copolymer (weak polyelectrolyte), and lecithin was used as a surfactant. Chitosan in different molecular weights and degrees of acetylation were adsorbed on lecithin-stabilized nanoemulsion droplets to examine how the stability was affected by the electrophoretic mobility [21]. Since the cationic surfactants could be generated from chitosan with amine and amino groups in combination with H+ ions, it was used as a cationic emulsifier to examine the suitability in preparing cationic bitumen emulsions [22]. Generally speaking, acetic acids were used to disperse chitosan in aqueous media. To modify their flavor, the oil-in-water emulsions were prepared by dispersing chitosan in lactic acid aqueous solutions first to evaluate their stability [23]. Some studies have found that long-term stable emulsions and Pickering emulsions of food-grade oil could be obtained by using chitosan as an emulsifier at different pH values [24; 25]. Besides examining the stability of emulsions, some studies have endeavored toward improving the emulsification efficiency. To obtain a more hydrophobic substrate for bacterial cell surfaces, association of the chitosan solution with _Escherichia coli_ was studied, and the results indicated that the emulsification efficiency was increased with increases in chitosan concentration [26]. In addition, a tapioca-starch suspension with addition of hydrophobic substance, such as a combination of chitosan-palm olein emulsion, was used to stabilize the PO (palm olein) droplets, and their stabilization was verified by elongation at break and water vapor permeability [27]. Other emulsion properties including antimicrobial activity, water-binding sites, nanostructural evolution, and emulsion breakdown were also discussed in the literature. For example, chitosan in different molecular weights and degrees of deacetylation was used in preparing oil-in-water emulsions, and their antimicrobial efficiencies were tested [28]. Carboxymethyl-hexanoyl chitosan amphiphilic hydrogel was synthesized as a carrier for delivering amphipatic agents, and results showed that the water-absorption ability was affected by the number of water-binding sites and the state of water under low humidity and the fully swollen state, respectively [22]. In addition, their water-absorption ability and drug encapsulation efficiency were defined to assess their performance. Similarly, the self-assembly capability of carboxymethyl-hexanoyl chitosan was employed to increase encapsulation efficiency [29]. Therefore, how the nanostructural stability was affected by the self-assembly mechanism was investigated by the critical aggregation concentration and zeta potential of the amphiphilic chitosan. To explore the mechanism of chitosan binding with fat, images of chitosan-oil aggregation were captured to examine the interaction between chitosan and oil-in-water droplets during the emulsification process [30]. Experimental results showed that the emulsion breakdown was enhanced with increases in viscosity and the degree of deacetylation of chitosan.