Abstract: The effects of medium parameters such as temperature, pH and initial number of microorganism on the inactivationof Escherichia coli, Staphylococcus aureus, Saccharaomyces cerevisiae & Bacillus subtilis subjected to pulsed magnetic fields wasstudied. Results showed: The survival rate of microorganism ran down with an increase in temperature. Furthermore, thetemperatures employed in the present study were far below pasteurization temperature. The survival rate was maximum at pHfrom 6 to 7, while the bactericidal effect became better with pH less than 5. The survival rate of microorganism ran down withan increase in the concentration of Na+. The higher the concentration of Na+ was, the better the bactericidal effect. The survivalrate of microorganism ran down with an increase in the initial number of microorganism. The higher the initial number ofmicroorganism was the better the bactericidal effect. The bactericidal effect was different to different species of microorganism.As a whole, the survival rate of S.cerevisiae was low while, the survival rate of B.subtilis was high. The survival rate of S.cerevisiaeran up with an increase in the content of dextrose or lactose. The higher the content of dextrose or lactose was, the poorer thebactericidal effect. The survival rate of S.cerevisiae ran down with an increase in the content of alcohol. The higher content ofalcohol was, the better the bactericidal effect. The survival rate of S.cerevisiae ran up with an increase in the content of peptone.The higher the content of peptone was, the poorer the bactericidal effect. The survival rate of S.cerevisiae ran down with an increasein the content of casein. The higher the content of casein was, the better the bactericidal effect.

Key words: pulsed magnetic field, temperature, pH, initial number of microorganism