Abstract: The preservative effects of chitosa ns with different concentrations an d solubility and modified atmosphere packaging(MAP)with different gas ratio on the chilled fresh pork were studied in this pap er.The result showed that chitosan hada distinct preservativ e effect.The higher concentration,the better preservationeffect.The acid -soluble chitosan had a better effect than water -soluble chitosan.The meat treated with1.5percent acid -soluble chitosan could be preserved for6days,but the meat had a sourness flav our.Comparedwithchitosan,MAPhad a better preser-vative effectandthe meathada bette r sensory quality.The meatpackaged withthe gas ratio of50%O 2 +25%CO2 +25% N2 couldbepreservedformorethan7days.ThehighertheratioofCO2 ,thebettertheeffect.Themeatpack agedwithanO 2 ratio of more than50%had a good freshredcolor.

Key words: Chilled freshpork , Preservation , Chitosan , Modufied atmosphere packaging