パルス キョウデンカイ ト オンネツ オ クミアワセタ エキラン ノ コウヒンシツ サッキン ニ カンスル ケンキュウ

博士(工学)熊本大

Inactivation of Enterobacter Aerogenes in Carboxymethyl Cellulose Solution using Intense Pulsed Electric Fields (iPEF) Combined with Moderate Thermal Treatment

This paper describes low-temperature sterilization of Enterobacter aerogenes incarboxymethyl cellulose solution using intense pulsed electric fields (iPEF) combinedwith moderate thermal energy. The bacterial suspension was exposed to moderatetemperatures of up to 55ºC for 2 minutes after tens of 530 ns-long, 50 kV/cm pulses in asingle-pass continuous flow system. Suspension temperatures at the entrance and exit ofthe iPEF exposure chamber were maintained at 40ºC by means of an electrode coolingsystem. The iPEF combined with subsequent thermal energy of 55ºC reduced bacterialpopulation by 6.6 Log10 cycles or more, compared with a reduction of only 2.1 Log10cycles by iPEF without heat treatment. Sterilization effects increased with increasingthermal treatment temperature and pulse number. Results obtained after culturing theiPEF-exposed bacteria in NaCl rich agar, which hinders the reorganization of thedamaged membrane, implies that even bacteria surviving the iPEF exposure aredamaged to some extent though may later recover. Bacteria were made vulnerable tosubsequent thermal treatment by iPEF-induced membrane damage. This indicates thatmoderate thermal stress after iPEF exposure increases sterilization effects