Surfactants and proteins have hydrophobe/hydrophilic segments and therefore they are surface active and can stabilise emulsion. As far as I am aware, chitosan does not have a hydrophobe segment (unless modified) and it is not surface active. Thus, you need to initially produce emulsion and then add chitosan to achieve the required property. 

I'm not that sure, as Elijah, because chitosan has amino groups which have positive charges at low pH, hence very hydrophilic, not very surface active, but become uncharged, above their pKa, which lies around pH 6 (you'd better check it up - my memory . . ). If you like to make an o/w emulsion, the emulsifier must be more soluble in the organic phase. Then, why not try with the uncharged version of chitosan ?  You're right about that some polymers (a good example is polyvinyl alcohol) and proteins(which all are surface active) are excellent emulsifier, since they also contribute to the physical stability by their high viscosities. Just keep in mind that the emulsifying efficacy is also dependent on their Molecular weights. I'd be very interested of your progress, if you try with chitosans. - I've never heard of someone trying that before. You could maybe become a pioneer in that field ! Good Luck !  / Johan Carlfors at:  www.ontargetchemistry.com

I agree with Elijah and Johna's answers.  Do watch the solubility of chitosan if you try this --- as the charge is reduced via pH change on those amino groups the material will become insoluble.  Degree of acetylation variation do exist for chitosan, plus the potential to use bulky anions -- so maybe enough variation exists to find a corner of the phase space where you could make an O/W emulsion.  Good hunting!

Mike

The short answer is "No". Chitosan is a polysaccharide - a string of sugar molecules. Sugar is highly water soluble. The acetyl groups are insufficient to make it surface-active. Polysaccharides that are emulsifiers, gum Arabic for instance, contain significant amounts of protein, which make the amphiphilic.

Thanks for your inputs. @Johan and Mike: When I try with uncharged version of chitosan, its insoluble in water. So I dissolved the Chitosan at acidic pH and then brought the pH for around 6-6.5 to make it neutral charge. When I moved for emulsification (high speed), emulsion is not stable. Probably the concentration of Chitosan may not be sufficient to make stable emulsion. I've to optimize the Chitosan amount. 

@ Alan: Yea, its a polysaccaride, but its merely insoluble in water. 

Besides many opinions that are already published and valuable, it is need kep in mind that different chitosans have different molecular weights  with different solubilities. Maybe it is not unreasonable to make experiments with chitosans that have low molecular weight

Chitosan is a good stabilizer for emulsions, but cannot behave as a suitable emulsifier like protein or surfactants, basically because chitosan does not reduce the interfacial tension. Some authors have reported certain interfacial properties for chitosan, although very weak to favour the emulsification process (they may be due to the presence of some residual protein in commercial chitosan). However, chitosan seems to contribute an enhancement of the interfacial elasticity of O/W layers, such that the combination of protein and chitosan has proven to be a good strategy for emulsion formation and stabilization.

I agree with Dr. Antonio Guerrero in every respect.

I'm nor that sure, even being a polysaccharide, chotosan or chitin, may have surface activtivity. It all depedns on its differences between the hydrophobic / hydrophilic domains of the molecule. Those are surely present, even being a polysaccharide.

Thank you all.