Zheng and Zhu (2003) found the effectiveness of chitosan (withthe molecular weight of less than 300 KDa) against Staphylococ-cus aureus [33]. Bacterial strain, incubation temperature and foodsubstrate are the main variables greatly determine the antimicro-bial activity of chitosan [34]. Previous works on chitosan revealedthat gram negative bacteria seemed to be more resistance againstchitosan probably due to their outer membrane [13,35].