Chitosan powder

A process according to any preceding claim wherein the chitosan powder has a moisture content of less than about 20% and a concentration of impurities of less than about 12% by weight thereof.

A process according to any preceding claim wherein the chitosan powder has a volume mean particle size of from about 5 to about 50 μm.

A process according to any preceding claim wherein the chitosan powder has a porosity, as calculated by mercury porosimetry, of from about 0.45 cm3/g to about 0.8 cm3/g and wherein at least 80% by volume of the pores have a radius of from about 200 nm to about 5,000 nm.

A process for making nano-sized chitosan by wet milling micro-sized chitosan in a mill comprising an apertured screen and a grinding medium of uniform size and wherein the process comprises at least two size reduction steps wherein the mean size of the medium of the first step is at least three times the mean size of the medium of the second step and wherein preferably the size of the screen apertures in each step is smaller than the corresponding mean size of the medium and at least twice the mean starting size of the micro-sized material.

A process for making nano-sized chitosan by wet milling micro-sized chitosan having a mean volume particle size of less than 50 μm and less than 5% of particles having a particle size greater than 100 μm.

Micro-sized chitosan powder wherein the Minimum Inhibitory Concentration for Malassezia furfur and for Staphylococcus epidermidis is less than about 100 ppm.