Effect of pulsed electric fields on inactivation of microbe and quality of freshly-squeezed pear juice

To evaluate the application of non-thermal processing technology on the processing of freshly-squeezed pear juice, the effects of pulsed electric fields on inactivation of microbe and quality of freshly-sequeezed pear juice were investigated.The results showed that E. coli and S. cerevisiae inoculated in pear juice reduced by 4.6 and 2.7 in logarithm when exposed to Pulsed Electric Fields(PEF) at 200 Hz, 30 kV/cm, 10℃, for 240 μs, respectively. With the promotion of temperature from 10 to 40℃, the reduction of E. coli and S. cerevisiae innoculated in pear juice, the total count of bacteria colonies, yeast and mold in the freshly-squeezed pear juice increased by 1.4, 2.0, 2.0 and 1.0 in logarithm, respectively by PEF treatment at 200 Hz, 30 kV/cm for 200 μs. The pear juice after PEF treatment was more close to untreated pear juice than the pasteurized pear juice in physico-chemical properties and nutrition .The result of Gas Chromatography-Mass Spectrometric(GC-MS) showed that the main volatile aroma compounds in pear juice was ester, and the treatment of PEF brought less influence on juice flavor than conditional thermal sterilization. It is concluded that PEF treatment can effectively inactivate the microbe and maintain the flavor and quality of pear juice.