Effects of High Pulsed Magnetic Field On Enzymes and Microorganisms In Strawberry Juice

This work is to evaluate the effects of high pulsed magnetic field (PMF) on enzymes, microorganisms and nutrient ingredient in strawberry juice, and discuss the mechanisms of PMF for sterilization and enzyme inactivation. Different HPMFs with the field strengths ranging from 9.3 to 19.0 tesla (T) for 3 to 12 pulses were applied. A maximum inactivation for polyphenol oxidase (PPO) was achieved by PMF at 17.3 T for 9 pulses, while for peroxidase (POD) was at 17.3 T for 12 pulses that 60 % of the enzyme was inactivated. Total bacterial number in strawberry juice reduced less than 100 cfu/mL without nutrition destroying at 17.3 T for 9 pulses or more, among them molds and yeasts were totally killed. In order to explore the mechanism of inactivating enzyme by high PMF, circular dichroism (CD) spectra and the fluorescence chromatography were applied to analyze the enzyme structure. They proved that alteration of the tertiary structure is the reason for the inactivation of POD under high PMF. Fluorescence microscope observation also proved that the damaged Aspergillus genus was increased with the increasing of magnetic field strength.