Abstract: The paper systematically studied the residual activities of POD, PPO and LOX enzymes in Hami melon juice pressurized at 500MPa for 3～20min, and its bacteria total count, target spore bacteria and E.coli as safety index bacteria were also treated at the same condition. The results showed that at 500MPa for 20min treatment, the pressure tolerance of POD was greater than that of PPO and LOX, their residual activities were 81%, 8.06% and 6.84% respectively, the spores were pressure- resistant, E.coli was sensitive to ultra high pressure and the pressurized melon juice reached the safety standards of FDA on fruit and vegetable juice nonthermal processing and the domestic beverage standards.

Key words: Hami melon juice, ultra high pressure, enzyme activity, bacteria, safety evaluation