【摘要】 近年来新兴的非热食品加工技术高压脉冲电场(PEF)处理温度低、节能、货架期长且能较好保持果蔬汁中的营养成分,而人们对食品品质的要求逐渐提高。为此,采用一套自行研发的高压脉冲食品非热处理系统,研究了PEF对植物乳杆菌和扩展青霉菌残活率的影响。当外加峰值为17 kV、420个脉冲电压时,乳酸杆菌和扩展青霉的对数残活率最大分别降低了约4.135和3.810。在处理室出口处放置热电偶来监测物料温度,测得数据表明,PEF处理会导致菌液温度升高。随电场强度增强和脉冲数增加,不冷却回路处理后比冷却回路处理后菌液温度增加幅度增大,在外加峰值电压分别为8、13和15 kV时前者比后者的菌液温度增加幅度分别在2-8、3-10、3-17°C。在电压峰值为15 kV、420个脉冲时菌液温度最高增加了30°C。试验结果表明,随着外加脉冲电压及脉冲数的增加,两种细菌的残活率都有显著下降,且微生物对PEF的敏感性增强,乳酸杆菌对PEF敏感性强于扩展青霉。更多还原

【Abstract】 The effect of high Pulsed Electric Field treatment on lactobacillus plantarum and Penicillium expansum is studied in this paper.A continuous laboratory-size system for the nonthermal pasteurization of liquid foods with PEF technology is used in the experiment which can provide monopolar exponentially-decaying wave pulse with pulsed duration ranged 0.1~50 μs and peak pulsed voltage ranged 1~50 kV and the repetition rate is 1Hz.The treatment chamber of this experiment is a coaxial-electrodes shape chamber with a volume of 60mL.The fraction of surviving cells of both bacteria in various conditions is tested through changing electric field intensity and pulse number.There is a about 4.135 log reduction of surviving lactobacillus plantarum cells achieved with a peak pulsed voltage of 17 kV at 420 pulses,for Penicillium expansum,there is a about 3.810 reduction.During the experiment,fluid temperature i monitored by a thermocouple set in the outlet end of the treatment chamber.The data show that the temperature of the fluid increases after the treatment when there is no cooling system and the temperature increases with the increase in the applied pulsed voltage and pulsed number.When the applied pulsed voltage is 8 kV,13 kV and 15 kV,the temperature increased by 2~8°C,3~10°C and 3~17°C,respectively,a highest temperature addition of 30°C is achieved after the PEF treatment for 15 kV and 420 pulsed number.The experimental results indicate that the surviving rate(S) of lactobacillus plantarum and Penicillium expansum decrease when the applied electric field intensity and pulse numbers increase,and the two bacteria become more sensitive to PEF as the electric field intensity increasing and the lactobacillus plantarum is more sensitive to PEF treatment than the Penicillium expansum.更多还原