Chitosan solutions were prepared by dissolving chitosan flakes (0.5, 1 and 1.5 g) in distilled water (80 mL) containing 0.7 mL of lactic acid (Sigma) under agitation using a magnetic stirrer, incubated over night at room temperature (22C). The pH of the solution was adjusted to 5.5 with 0.46 M K2HPO4 (Sigma–Aldrich) and the solution was made up to 100mL with distilled water. Glycerol (25% p/p of chitosan) was added and the solution was stirred at ambient temperature for 30 min.