JP4106800B2

JP4106800B2 - High electric field pulse sterilization method and apparatus

Info

Publication number: JP4106800B2
Application number: JP07567299A
Authority: JP
Inventors: 隆司真島; 秀典秋山; 淳勝木
Original assignee: IHI Corp
Current assignee: IHI Corp
Priority date: 1999-03-19
Filing date: 1999-03-19
Publication date: 2008-06-25
Anticipated expiration: 2019-03-19
Also published as: JP2000262261A

Description

【０００１】
【発明の属する技術分野】
本発明は、飲料などの液体を殺菌するために用いる高電界パルス殺菌方法及び装置に関するもので、特に、熱耐性菌の如き比較的頑強な芽胞菌の殺菌に有利な高電界パルス殺菌方法及び装置に関するものである。
【０００２】
【従来の技術】
飲料などの液体の殺菌方法の一つとして、対峙するよう配した一対の電極間に殺菌対象液体を配置し、上記両電極間に高電界パルスを、１００ｎｓ以上の比較的長いパルス波形の幅で印加し、該高電界パルスによって生じる衝撃波や電場を殺菌対象液体中の微生物に作用させることにより、該微生物の構成物であるＤＮＡや膜を破壊すべく物理的なダメージを与えて、上記殺菌対象液体の殺菌処理を行うようにする高電界パルス殺菌方法が、既に提案されている（特開昭６２−１５１１７４号、特開平１−９５７５１号参照）。
【０００３】
上記高電界パルス殺菌方法では、一般的に、印加される高電界パルスの電界強度と、菌の生存率との関係を図３に示す如く、同一パルス幅（たとえば１０μｓ）で且つ同一ショット数（たとえば１００ｓｈｏｔｓ）ならば、殺菌対象液体に印加する高電界パルスの電界強度が高くなるに従って、生菌率が低くなる、すなわち、殺菌効果が高くなることが確認されている。
【０００４】
【発明が解決しようとする課題】
ところが、上記従来の高電界パルス殺菌方法では、高電界パルスを発生させる際、１００ｎｓ以上となる比較的長いパルス幅の高電界パルスを生じさせるようにしていたため、殺菌効果を高めることを目的として高電界パルスの電界強度を高めようとすると、異常放電による絶縁破壊（放電全路破壊）を起こし易くなることから、電界強度をあまり高いものとすることができず、したがって、殺菌効果をあまり高いものとすることができず、熱耐性菌であるバチルスステアロサーモフィルスの如き比較的頑強な芽胞菌の殺菌を行うことができないという問題があり、又、殺菌処理を行う場合、微生物のみならず、殺菌対象液体自体の質に変化を生じさせ易く、更に、殺菌対象液体に温度上昇を引き起こし易いという問題もある。
【０００５】
そこで、本発明は、殺菌対象液体に変質や温度上昇を引き起こすことなく、上記の如き比較的頑強な芽胞菌の殺菌処理をも行うことのできる高電界パルス殺菌方法及び装置を提供しようとするものである。
【０００６】
【課題を解決するための手段】
本発明は、上記課題を解決するために、所要間隔で対峙させた電界印加電極間に形成される高電界印加領域に殺菌対象液体を注入して配置し、該電界印加電極の対峙間隔を、高電界パルスが立ち上がり時間を１００ｐｓ〜２０ｎｓ未満、パルス幅を１００ｎｓ未満、立ち下がり時間を１００ｐｓ〜１００ｎｓ以下としてあるときに一方の電界印加電極から放電により放出された電子が移動して他方の電界印加電極に達しない距離として、上記高電界印加領域の殺菌対象液体に、立ち上がり時間を１００ｐｓ〜２０ｎｓ未満、パルス幅を１００ｎｓ未満、立ち下がり時間を１００ｐｓ〜１００ｎｓ以下とし、且つ電界強度を３０〜３００ｋＶ／ｃｍとした高電界パルスを印加して殺菌を行わせる方法とし、又、殺菌対象液体を収容できるようにした空間部の両側に所要間隔で対峙させた一対の平板状の電界印加電極を配設して、該電界印加電極の対峙間隔を、高電界パルスが立ち上がり時間を１００ｐｓ〜２０ｎｓ未満、パルス幅を１００ｎｓ未満、立ち下がり時間を１００ｐｓ〜１００ｎｓ以下としてあるときに一方の電界印加電極から放電により放出された電子が移動して他方の電界印加電極に達しない距離として、該電界印加電極間を高電界印加領域とし、且つ上記高電界印加領域に注入されて配置された殺菌対象液体に対して、立ち上がり時間を１００ｐｓ〜２０ｎｓ未満、パルス幅を１００ｎｓ未満、立ち下がり時間を１００ｐｓ〜１００ｎｓ以下とし且つ電界強度を３０〜３００ｋＶ／ｃｍとした高電界パルスを印加させるための短パルス発生装置を備えてなる装置とする。
【０００７】
高電界印加領域に注入された殺菌対象液体に、高電界パルスが印加されるようになると、印加された高電界パルスにより生じる衝撃波や電場により、殺菌対象液体中の微生物には物理的ダメージが与えられて、殺菌されるようになる。この際、印加される高電界パルスは、異常放電による絶縁破壊に至る前の時間でパルスを終わらせることができて、絶縁破壊を引き起こす異常放電の発生を大幅に減少させることができ、絶縁破壊を引き起こすことなく印加する高電圧パルスの電界強度を高めることができる。
【０００８】
又、絶縁体製容器と該絶縁体製容器の外周に連結して一体的とした導体製共振空洞との間に形成される高電界印加領域に、少なくとも５０ＭＨｚ以上としてある周波数のマイクロ波を照射して、上記絶縁体製容器内を通して上記高電界印加領域に導かれた殺菌対象液体に対して、電界強度を３０〜３００ｋＶ／ｃｍとした高電界パルスを印加して殺菌を行わせる方法とし、又、一方向より流す殺菌対象液体を所定時間収容することができるようにしてある絶縁体製容器の外周に導体製共振空洞を一体的に連結して、該導体製共振空洞と絶縁体製容器との間に高電界印加領域を形成し、且つ該高電界印加領域に少なくとも５０ＭＨｚ以上としてある周波数のマイクロ波を照射して該高電界印加領域に導かれた殺菌対象液体に対して電界強度を３０〜３００ｋＶ／ｃｍとした高電界パルスを印加するためのマイクロ波発生装置を備えてなる装置とする。
【０００９】
マイクロ波発生装置により発生させたマイクロ波を高電界印加領域に照射すると、マイクロ波は電界と磁界を含んだ空間伝播波であることから高電界印加領域に高電界パルスが発生させられて、高電界印加領域内の殺菌対象液体に高電界パルスが印加され、殺菌対象液体中の微生物に対して物理的ダメージが与えられる。この際、マイクロ波における５０ＭＨｚ以上の周波数は、印加される高電界パルスにおいては最大で１０ｎｓ程度の短いパルス幅に相当するものとなることから、絶縁破壊を引き起こすことなしに印加する高電界パルスの電界強度を高めることができる。
【００１０】
【発明の実施の形態】
以下、本発明の実施の形態を図面を参照して説明する。
【００１１】
図１（イ）（ロ）は本発明の高電界パルス殺菌方法及び装置の実施の一形態を示すもので、所要の板厚、たとえば５ｍｍ厚としてある絶縁体製の平板３ａの中央部に殺菌対象液体を入れておくことができる大きさの貫通孔１を設けると共に、該貫通孔１の上端内面に開口するように上記平板３ａの上端より板厚中心部を延びる細孔２を穿設して、細孔２を通して貫通孔１部に殺菌対象液体を入れるようにした殺菌容器としてのスペーサ３を形成し、該スペーサ３の中央部分の両側面に、上記貫通孔１を両側から閉塞させるように平板状の電界印加電極４をそれぞれスペーサ３の両側面に接触させて対称的に配置して、上記貫通孔１の内周面と両電界印加電極４との間に形成される空間部を高電界印加領域５とし、更に、上記各電界印加電極４に、所要のパルス幅となり且つ所要強度の電圧パルスを発生させるための短パルス発生装置６を、配線７を介して接続した構成とし、上記スペーサ３の細孔２を通して高電圧印加領域５内に殺菌対象液体８を注入し、且つ上記短パルス発生装置６で発生させた電圧パルスを、配線７を通して各電界印加電極４に導くことにより、上記両電界印加電極４間に配置させた殺菌対象液体８に対して、立ち上がり時間を１００ｐｓ〜２０ｎｓ未満、パルス幅を１００ｎｓ未満、立ち下がり時間を１００ｐｓ〜１００ｎｓ以下とし、且つ電界強度を３０〜３００ｋＶ／ｃｍとした高電界パルスを印加させるようにする。
【００１２】
上記各電界印加電極４は、スペーサ３の貫通孔１の径より大きな径の円盤状とすると共に、反スペーサ３側の面の外周縁部に全周にわたって丸い突部４ａを形成したロゴウスキー電極構造として、両電界印加電極４間に均一な電界を発生させることができるようにしてある。
【００１３】
又、上記配線７としては、１ｍｍ厚程度までの銅板を用いるようにすると共に、各電界印加電極４と短パルス発生装置６との物理的及び３次元構造的な距離をできるだけ減らして接続するようにして、配線７におけるインダクタンス、キャパシタンス、純抵抗を減らして低インピーダンスとなるようにしてある。
【００１４】
なお、９は対向面部に設けた一対の支持装置１０によりスペーサ３と両電界印加電極４とを一体に挟持するための筐体である。
【００１５】
殺菌対象液体８の殺菌処理を行う場合には、先ず、殺菌対象液体８をスペーサ３の細孔２を通して貫通孔１部分の高電界印加領域５に注入した後、短パルス発生装置６により電圧パルスを発生させて、上記高電界印加領域５内における殺菌対象液体８に高電界パルスを印加させるようにする。これにより、印加された高電界パルスにより生じる衝撃波や電場により、上記殺菌対象液体８中の微生物のＤＮＡや細胞膜を破壊させるような物理的ダメージが与えられて、殺菌されるようになる。
【００１６】
上記において、印加される高電界パルスは、立ち上がり時間を１００ｐｓ〜２０ｎｓ未満、パルス幅を１００ｎｓ未満、立ち下がり時間を１００ｐｓ〜１００ｎｓ以下としてある。ここで、一般に５ｍｍのギャップ長を設けて配してある一対の並行平板電極において、数十ｎｓというのは、一方の平板電極から放電により放出された電子が移動して他方の平板電極に達するかどうかという領域の時間単位でしかないことから、本発明で用いる上記高電界パルスは、異常放電による絶縁破壊に至る前、すなわち、放電全路破壊を起こす前に、印加されるパルスを終わらせることができ、したがって、絶縁破壊を引き起こす異常放電が発生する虞を大幅に減少させることができることから、絶縁破壊を引き起こすことなしに印加する高電圧パルスの電界強度を高めることができる。
【００１７】
このように、従来に比してより電界強度の高い高電界パルスを殺菌対象液体８に印加することができることから、殺菌対象液体８中の微生物に付与する物理的ダメージの強度を高めることができて、従来の高電界パルス殺菌法では殺菌し得なかったバチルスステアロサーモフィルスの如き比較的頑強な芽胞菌の殺菌を行うことができ、又、高電界パルスの電界強度を高めることにより、パルス幅を短くしても高い殺菌効果を得ることができることから、従来と同等の殺菌効果を得るために要する、殺菌対象液体８に対して電界を印加している時間の総和を短くすることができて、非加熱的に殺菌処理を行うことができ、更に、高電界パルスのパルス幅を短くしていることから、殺菌対象液体８中の電子やイオンが移動する時間が短くなり、したがって該電子やイオンの動きや反応を制限することができて、殺菌対象液体８自体の変質を防止することできる。
【００１８】
因みに、殺菌対象液体８に印加する高電界パルスの電界強度を３０〜３００ｋＶ／ｃｍとしたのは、３００ｋＶ／ｃｍを空気中で超える場合には、たとえパルス幅を１００ｎｓ未満としても絶縁破壊を防ぐことが難しく、現状の技術では装置が実用的でないものとなり、一方、３０ｋＶ／ｃｍ以下の場合には、微生物に対して、殺菌に至る物理的ダメージを効果的に付与することができず、芽胞菌を殺菌できないからである。
【００１９】
次に、図２は本発明の実施の他の形態を示すもので、一方向より所定流速で流す殺菌対象液体８を所定時間収容することができるよう、所要長さとしてあるセラミックス、ガラス、プラスチック等の絶縁体製容器としての管１１の外周に、該管１１の中間部を取り囲む大径の導体製共振空洞１２と、管１１の両端部をそれぞれ取り囲む小径の導体製導波管１３とをそれぞれ同軸心上に配して一体的に連結し、上記共振空洞１２と管１１の中間部との間に形成される空間部を、高電界印加領域１４とし、更に、共振空洞１２の外周部所要個所に、マイクロ波発生装置１５からマイクロ波１６を導くためのマイクロ波入力部１７を設けた構成とし、マイクロ波発生装置１５にて発生させた少なくとも５０ＭＨｚ以上としてある周波数のマイクロ波１６をマイクロ波入力部１７より共振空洞１２内に導き、該マイクロ波１６により、管１１内を通して上記高電界印加領域１４に導かれた殺菌対象液体８に対して、電界強度を３０〜３００ｋＶ／ｃｍとした高電界パルスを印加させるようにする。
【００２０】
本実施の形態の装置を用いて殺菌処理を行う場合は、先ず、管１１に所定速度で殺菌対象液体８を流しながら、マイクロ波発生装置１５により発生させたマイクロ波１６を、マイクロ波入力部１７を介して共振空洞１２内に入力させるようにすると、マイクロ波１６は電界と磁界を含んだ空間伝播波であることから導波管１３及び共振空洞１２により集束させられて高電界印加領域１４に高電界パルスを発生させるようになり、したがって、高電界印加領域内で管１１内を流れる殺菌対象液体８に順次高電界パルスが印加されるようになり、これにより、上記実施の形態と同様に、殺菌対象液体８中の微生物に対しては物理的ダメージが与えられることから、殺菌対象液体８は連続的に殺菌処理されるようになる。
【００２１】
この際、マイクロ波１６における５０ＭＨｚ以上の周波数は、印加される高電界パルスにおいては最大で１０ｎｓ程度の短いパルス幅に相当するものとなることから、絶縁破壊を引き起こすことなしに印加する高電界パルスの電界強度を高めることができる。
【００２２】
したがって、本実施の形態によっても、上記実施の形態と同様な効果を得ることができる。
【００２３】
なお、本発明は上記実施の形態のみに限定されるものではなく、図１（イ）（ロ）の実施の形態において、高電界印加領域５はスペーサ３に設けた貫通孔１と、ロゴウスキー電極構造とした一対の電界印加電極４とにより形成するものとして示したが、所要間隔で対峙して、均一電界を生じさせるための一対の電界印加電極間に殺菌対象液体８を所定時間配置することができるようにすれば、高電界印加領域５は、自在に形成してよいこと、一対の電界印加電極４間の間隔は、所望する高電界パルスの電界強度と、短パルス発生装置で発生させる電圧パルスの電圧に応じて自在に決定してよいこと、又、図２の実施の形態において、高電界印加領域１４を形成するために、殺菌対象液体８を通す管１１の外周に、導波管１３と、連続した共振空洞１２とを設けてマイクロ波１６を集束させるようにしていたが、殺菌対象液体８を所定時間収容する絶縁体製容器にマイクロ波１６を集束させて照射することができれば、開放型共振空洞や進行波管を用いてもよく、更に、大部屋内にダイポールやパラボラなどのアンテナを設置して殺菌対象液体の収容容器に向けて直接マイクロ波１６を照射するようにしてもよいこと、高電界パルスのパルス幅や、電界強度、ショット数等をコントロールして微生物に作用させることにより、微生物活動を抑制する静菌的作用を発揮させ、これにより食品の長期保存や発酵、醸造の制御に適用することも可能であること、その他、本発明の要旨を逸脱しない範囲内において種々変更を加え得ることは勿論である。
【００２４】
【実施例】
本発明者等の行った実験結果について説明する。
【００２５】
実施例１
図１に示す装置の高電界印加領域に、殺菌対象液体８のサンプルとして、バチルスステアロサーモフィルス（ＡＴＣＣ＃１２９８０）の培養液を注入し、電界印加電極に短パルス発生装置にて発生させた電圧パルスを流すことにより、上記サンプルに対して、立ち上がり時間を１ｎｓ、パルス幅を８０ｎｓ、立ち下がり時間を２ｎｓとし、且つ電界強度を１２０ｋＶ／ｃｍとした高電界パルスを、ショット数１００００ｓｈｏｔｓとして印加させた。
【００２６】
本実施例により、サンプル中のバチルスステアロサーモフィルスに対する殺菌効果が確認された。
【００２７】
【発明の効果】
以上述べた如く、本発明の高電界パルス殺菌方法及び装置によれば、所要間隔で対峙させた電界印加電極間に形成される高電界印加領域に殺菌対象液体を注入して配置し、該電界印加電極の対峙間隔を、高電界パルスが立ち上がり時間を１００ｐｓ〜２０ｎｓ未満、パルス幅を１００ｎｓ未満、立ち下がり時間を１００ｐｓ〜１００ｎｓ以下としてあるときに一方の電界印加電極から放電により放出された電子が移動して他方の電界印加電極に達しない距離として、該高電界印加領域の殺菌対象液体に、立ち上がり時間を１００ｐｓ〜２０ｎｓ未満、パルス幅を１００ｎｓ未満、立ち下がり時間を１００ｐｓ〜１００ｎｓ以下とし、且つ電界強度を３０〜３００ｋＶ／ｃｍとした高電界パルスを印加して殺菌を行わせる方法、及び、殺菌対象液体を収容できるようにした空間部の両側に所要間隔で対峙させた一対の平板状の電界印加電極を配設して、該電界印加電極の対峙間隔を、高電界パルスが立ち上がり時間を１００ｐｓ〜２０ｎｓ未満、パルス幅を１００ｎｓ未満、立ち下がり時間を１００ｐｓ〜１００ｎｓ以下としてあるときに一方の電界印加電極から放電により放出された電子が移動して他方の電界印加電極に達しない距離として、該電界印加電極間を高電界印加領域とし、且つ上記高電界印加領域に注入されて配置された殺菌対象液体に対して、立ち上がり時間を１００ｐｓ〜２０ｎｓ未満、パルス幅を１００ｎｓ未満、立ち下がり時間を１００ｐｓ〜１００ｎｓ以下とし且つ電界強度を３０〜３００ｋＶ／ｃｍとした高電界パルスを印加させるための短パルス発生装置を備えてなる装置としてあり、又、絶縁体製容器と該絶縁体製容器の外周に連結して一体的とした導体製共振空洞との間に形成される高電界印加領域に、少なくとも５０ＭＨｚ以上としてある周波数のマイクロ波を照射して、上記絶縁体製容器内を通して上記高電界印加領域に導かれた殺菌対象液体に対して、電界強度を３０〜３００ｋＶ／ｃｍとした高電界パルスを印加して殺菌を行わせる方法、及び、一方向より流す殺菌対象液体を所定時間収容することができるようにしてある絶縁体製容器の外周に導体製共振空洞を一体的に連結して、該導体製共振空洞と絶縁体製容器との間に高電界印加領域を形成し、且つ該高電界印加領域に少なくとも５０ＭＨｚ以上としてある周波数のマイクロ波を照射して該高電界印加領域に導かれた殺菌対象液体に対して電界強度を３０〜３００ｋＶ／ｃｍとした高電界パルスを印加するためのマイクロ波発生装置を備えてなる装置としてあるので、絶縁破壊を引き起こすことなしに印加する高電圧パルスの電界強度を高めることができ、これにより、従来に比してより電界強度の高い高電界パルスを殺菌対象液体に印加して、殺菌対象液体中の微生物に付与する物理的ダメージの強度を高めることができ、従来の高電界パルス殺菌法では殺菌し得なかった比較的頑強な芽胞菌の殺菌を行うことができ、又、高電界パルスの電界強度を高めることで、パルス幅を短くしても高い殺菌効果を得ることができることから、殺菌対象液体に対して電界を印加している時間の総和を従来に比して短くすることができて、殺菌処理を非加熱的なものとすることができ、更に、電子やイオンの動きや反応を制限することができて、殺菌対象液体自体の変質を防止することできるという優れた効果を発揮する。
【図面の簡単な説明】
【図１】本発明の高電界パルス殺菌方法及び装置の実施の一形態を示すもので、（イ）は概略切断正面図、（ロ）は（イ）のＡ−Ａ矢視図である。
【図２】本発明の他の実施の形態を示す一部切断概略斜視図である。
【図３】高電界パルス殺菌方法における印加される高電界パルスの電界強度と菌の生存率との関係を示すグラフである。
【符号の説明】
４電界印加電極
５高電界印加領域
６短パルス発生装置
８殺菌対象液体
１１管（絶縁体製容器）
１５マイクロ波発生装置
１６マイクロ波[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high electric field pulse sterilization method and apparatus used for sterilizing liquids such as beverages, and in particular, a high electric field pulse sterilization method and apparatus advantageous for sterilization of relatively robust spore bacteria such as heat resistant bacteria. It is about.
[0002]
[Prior art]
As one method for sterilizing liquids such as beverages, a liquid to be sterilized is placed between a pair of electrodes arranged to face each other, and a high electric field pulse is applied between the electrodes with a relatively long pulse waveform width of 100 ns or more. By applying a shock wave or electric field generated by the high electric field pulse to the microorganism in the liquid to be sterilized, causing physical damage to destroy the DNA or film that is a component of the microorganism, A high electric field pulse sterilization method for sterilizing a liquid has been proposed (see Japanese Patent Laid-Open Nos. 62-151174 and 1-95751).
[0003]
In the high electric field pulse sterilization method, generally, the relationship between the electric field intensity of the applied high electric field pulse and the survival rate of the bacteria is shown in FIG. 3, with the same pulse width (for example, 10 μs) and the same number of shots ( For example, in the case of 100 shots), it has been confirmed that as the electric field strength of the high electric field pulse applied to the liquid to be sterilized increases, the viable bacteria rate decreases, that is, the sterilizing effect increases.
[0004]
[Problems to be solved by the invention]
However, in the conventional high electric field pulse sterilization method, when a high electric field pulse is generated, a high electric field pulse having a relatively long pulse width of 100 ns or more is generated. If an attempt is made to increase the electric field strength of the electric field pulse, dielectric breakdown (discharging whole-path breakdown) is likely to occur due to abnormal discharge, so the electric field strength cannot be made very high, and therefore the sterilization effect is too high. There is a problem that it is not possible to sterilize relatively robust spore bacteria such as Bacillus stearothermophilus that is a heat-resistant bacterium, and when performing sterilization treatment, not only microorganisms, There is also a problem that the quality of the liquid to be sterilized itself is easily changed, and further, the temperature of the liquid to be sterilized is easily increased.
[0005]
Therefore, the present invention intends to provide a high electric field pulse sterilization method and apparatus capable of performing sterilization treatment of relatively robust spore bacteria as described above without causing alteration or temperature rise in the liquid to be sterilized. It is.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention injects and disposes a liquid to be sterilized in a high electric field application region formed between electric field application electrodes confronting each other at a required interval . When a high electric field pulse has a rise time of 100 ps to less than 20 ns, a pulse width of less than 100 ns, and a fall time of 100 ps to 100 ns or less, electrons emitted from one electric field application electrode move and the other electric field application As the distance that does not reach the electrode, the liquid to be sterilized in the high electric field application region has a rising time of 100 ps to less than 20 ns, a pulse width of less than 100 ns, a falling time of 100 ps to 100 ns or less, and an electric field strength of 30 to 300 kV / In order to sterilize by applying a high electric field pulse of cm, so that the liquid to be sterilized can be accommodated It was by arranging a pair of plate-shaped electric field applying electrodes were opposed at predetermined intervals on both sides of the space portion, the opposed spacing of the field application electrode, less than 100ps~20ns the rise time high electric field pulse, a pulse width When the fall time is less than 100 ns and the fall time is set to 100 ps to 100 ns or less, an electron discharged from one electric field application electrode moves and does not reach the other electric field application electrode. With respect to the liquid to be sterilized that is applied and disposed in the high electric field application region , the rise time is set to 100 ps to less than 20 ns, the pulse width is set to less than 100 ns, the fall time is set to 100 ps to 100 ns and the electric field strength. to become equipped with short-pulse generator device for applying a high electric field pulses and 30~300kV / cm to .
[0007]
When a high electric field pulse is applied to the liquid to be sterilized injected into the high electric field application region, the microorganisms in the liquid to be sterilized are physically damaged by the shock wave or electric field generated by the applied high electric field pulse. And become sterilized. At this time, the applied high electric field pulse can finish the pulse at a time before breakdown due to abnormal discharge, and can greatly reduce the occurrence of abnormal discharge causing breakdown. It is possible to increase the electric field strength of the high voltage pulse to be applied without causing the phenomenon.
[0008]
Also, microwaves having a frequency of at least 50 MHz or more are applied to a high electric field application region formed between the insulator container and the conductor resonant cavity connected to the outer periphery of the insulator container. to, for the sterilized liquid guided into the high electric field application region through the insulator steel vessel, and how to perform the sterilization by applying a high electric field pulses the field strength and 30~300kV / cm, Further, a conductor made resonant cavity outside periphery of the insulator made of container that is as a sterilized liquid can be accommodated given time to flow from one direction integrally connected, conductor made resonant cavity and the insulator made of A high electric field application region is formed between the container and the high electric field application region is irradiated with microwaves having a frequency of at least 50 MHz, and the electric field strength is applied to the liquid to be sterilized guided to the high electric field application region. 3 Device that made comprises a microwave generator for applying a high electric field pulses and ~300kV / cm.
[0009]
When the microwave generated by the microwave generator is irradiated to the high electric field application region, the microwave is a spatially propagated wave including an electric field and a magnetic field, so that a high electric field pulse is generated in the high electric field application region, A high electric field pulse is applied to the liquid to be sterilized in the electric field application region, and physical damage is given to microorganisms in the liquid to be sterilized. At this time, the frequency of 50 MHz or more in the microwave corresponds to a short pulse width of about 10 ns at the maximum in the applied high electric field pulse, and therefore the high electric field pulse applied without causing dielectric breakdown. The electric field strength can be increased.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0011]
FIGS. 1 (a) and 1 (b) show an embodiment of a high electric field pulse sterilization method and apparatus according to the present invention. The sterilization is performed at the center of a flat plate 3a made of an insulator having a required plate thickness, for example, 5 mm. A through hole 1 having a size capable of holding the target liquid is provided, and a pore 2 extending from the upper end of the flat plate 3a to the center of the plate thickness is formed so as to open on the inner surface of the upper end of the through hole 1. Then, a spacer 3 is formed as a sterilization container in which the liquid to be sterilized is put into one part of the through-hole through the pore 2, and the through-hole 1 is closed from both sides on both side surfaces of the central portion of the spacer 3. A flat electric field applying electrode 4 is arranged symmetrically in contact with both side surfaces of the spacer 3, and a space formed between the inner peripheral surface of the through hole 1 and both electric field applying electrodes 4 is formed. A high electric field application region 5 is provided. A short pulse generator 6 for generating a voltage pulse having a required pulse width and a required intensity is connected via a wiring 7 and is sterilized in the high voltage application region 5 through the pores 2 of the spacer 3. The target liquid 8 is injected, and the voltage pulse generated by the short pulse generator 6 is guided to each electric field application electrode 4 through the wiring 7, so that the sterilization target liquid 8 disposed between the two electric field application electrodes 4. On the other hand, a high electric field pulse with a rise time of 100 ps to less than 20 ns, a pulse width of less than 100 ns, a fall time of 100 ps to 100 ns or less, and an electric field strength of 30 to 300 kV / cm is applied.
[0012]
Each electric field applying electrode 4 has a disk shape having a diameter larger than the diameter of the through hole 1 of the spacer 3 and a Rogowski electrode structure in which a round protrusion 4 a is formed on the outer peripheral edge of the surface on the side opposite to the spacer 3. As described above, a uniform electric field can be generated between the two electric field applying electrodes 4.
[0013]
Further, as the wiring 7, a copper plate up to about 1 mm thickness is used, and the physical and three-dimensional structural distance between each electric field applying electrode 4 and the short pulse generator 6 is reduced as much as possible. Thus, the inductance, capacitance, and pure resistance in the wiring 7 are reduced to achieve a low impedance.
[0014]
Reference numeral 9 denotes a casing for integrally holding the spacer 3 and both electric field applying electrodes 4 by a pair of support devices 10 provided on the opposed surface portions.
[0015]
When the sterilization target liquid 8 is sterilized, first, the sterilization target liquid 8 is injected into the high electric field application region 5 of the through hole 1 through the pores 2 of the spacer 3, and then the voltage pulse is generated by the short pulse generator 6. And a high electric field pulse is applied to the sterilization target liquid 8 in the high electric field application region 5. As a result, the shock wave or electric field generated by the applied high electric field pulse causes physical damage that destroys the DNA or cell membrane of microorganisms in the liquid 8 to be sterilized, thereby sterilizing.
[0016]
In the above, the applied high electric field pulse has a rise time of 100 ps to less than 20 ns, a pulse width of less than 100 ns, and a fall time of 100 ps to 100 ns or less. Here, in a pair of parallel plate electrodes generally arranged with a gap length of 5 mm, tens of ns means that electrons emitted by discharge from one plate electrode move to reach the other plate electrode. Therefore, the high electric field pulse used in the present invention ends the applied pulse before breakdown due to abnormal discharge, that is, before breakdown of the entire discharge occurs. Therefore, since the possibility of occurrence of abnormal discharge that causes dielectric breakdown can be greatly reduced, the electric field strength of the high-voltage pulse applied without causing dielectric breakdown can be increased.
[0017]
As described above, since a high electric field pulse having a higher electric field strength than before can be applied to the sterilization target liquid 8, the strength of physical damage imparted to the microorganisms in the sterilization target liquid 8 can be increased. In addition, relatively strong spore bacteria such as Bacillus stearothermophilus that could not be sterilized by the conventional high electric field pulse sterilization method can be sterilized, and by increasing the electric field strength of the high electric field pulse, Since a high sterilization effect can be obtained even if the width is shortened, the total time during which an electric field is applied to the sterilization target liquid 8 required to obtain the same sterilization effect as before can be shortened. In addition, since the sterilization treatment can be performed without heating and the pulse width of the high electric field pulse is shortened, the time for the movement of electrons and ions in the liquid 8 to be sterilized is shortened. Be able to restrict the electron and ion movements and reactions Therefore, it possible to prevent the deterioration of the sterilized liquid 8 itself.
[0018]
Incidentally, the reason why the electric field intensity of the high electric field pulse applied to the liquid 8 to be sterilized is set to 30 to 300 kV / cm is to prevent dielectric breakdown even if the pulse width is less than 100 ns when exceeding 300 kV / cm in the air. However, in the case of 30 kV / cm or less, physical damage leading to sterilization cannot be effectively imparted to microorganisms, and the spore is difficult. This is because the bacteria cannot be sterilized.
[0019]
Next, FIG. 2 shows another embodiment of the present invention. Ceramics, glass, and plastic having a required length so that a liquid to be sterilized 8 flowing at a predetermined flow rate from one direction can be stored for a predetermined time. A large-diameter conductor resonant cavity 12 surrounding the intermediate portion of the tube 11 and a small-diameter conductor waveguide 13 surrounding both ends of the tube 11 are provided on the outer periphery of the tube 11 as an insulator container such as A space portion formed between the resonance cavity 12 and the intermediate portion of the tube 11 is formed as a high electric field application region 14 on the coaxial core and integrally connected thereto. A microwave input unit 17 for guiding the microwave 16 from the microwave generator 15 is provided at a required location, and a microwave having a frequency of at least 50 MHz generated by the microwave generator 15 is provided. 6 is introduced into the resonant cavity 12 from the microwave input unit 17, and the electric field strength is set to 30 to 300 kV / with respect to the liquid 8 to be sterilized guided to the high electric field application region 14 through the tube 11 by the microwave 16. A high electric field pulse of cm is applied.
[0020]
When performing the sterilization using the apparatus of the present embodiment, first, the microwave 16 generated by the microwave generator 15 while flowing the liquid 8 to be sterilized through the tube 11 at a predetermined speed, When the microwave 16 is a spatially propagated wave including an electric field and a magnetic field, the microwave 16 is focused by the waveguide 13 and the resonant cavity 12 and is applied to the high electric field applying region 14. Thus, a high electric field pulse is generated, and accordingly, a high electric field pulse is sequentially applied to the liquid to be sterilized 8 flowing in the tube 11 within the high electric field application region, and as a result, as in the above embodiment. In addition, since the microorganisms in the sterilization target liquid 8 are physically damaged, the sterilization target liquid 8 is continuously sterilized.
[0021]
At this time, the frequency of 50 MHz or more in the microwave 16 corresponds to a short pulse width of about 10 ns at the maximum in the applied high electric field pulse, and thus the high electric field pulse applied without causing dielectric breakdown. The electric field strength can be increased.
[0022]
Therefore, the present embodiment can provide the same effects as those of the above embodiment.
[0023]
The present invention is not limited only to the above-described embodiment. In the embodiment shown in FIGS. 1A and 1B, the high electric field application region 5 includes the through hole 1 provided in the spacer 3, the Rogowski electrode. Although shown as being formed by a pair of electric field applying electrodes 4 having a structure, the liquid 8 to be sterilized is disposed for a predetermined time between a pair of electric field applying electrodes for generating a uniform electric field at a required interval. The high electric field application region 5 may be formed freely, and the distance between the pair of electric field application electrodes 4 is generated by the desired electric field strength of the high electric field pulse and the short pulse generator. It may be determined freely according to the voltage of the voltage pulse, and in the embodiment shown in FIG. Tube 13 and continuous resonance The cave 12 is provided so as to focus the microwave 16. However, if the microwave 16 can be focused and irradiated on an insulating container that contains the liquid 8 to be sterilized for a predetermined time, an open-type resonant cavity, A traveling wave tube may be used, and an antenna such as a dipole or a parabola may be installed in a large room so that the microwave 16 is directly irradiated toward the container for the liquid to be sterilized. By controlling the pulse width, electric field strength, number of shots, etc. of the pulse to act on microorganisms, it exerts a bacteriostatic action that suppresses microbial activity, thereby applying it to long-term storage of food, fermentation, and brewing control Of course, various modifications can be added without departing from the scope of the present invention.
[0024]
【Example】
The results of experiments conducted by the inventors will be described.
[0025]
Example 1
A culture solution of Bacillus stearothermophilus (ATCC # 12980) was injected as a sample of the liquid 8 to be sterilized into the high electric field application region of the apparatus shown in FIG. 1, and the electric field application electrode was generated by a short pulse generator. By applying a voltage pulse, a high electric field pulse with a rise time of 1 ns, a pulse width of 80 ns, a fall time of 2 ns, and an electric field strength of 120 kV / cm is applied to the sample as a shot number of 10000 shots. It was.
[0026]
By this example, the bactericidal effect against Bacillus stearothermophilus in the sample was confirmed.
[0027]
【The invention's effect】
As described above, according to the high electric field pulse sterilization method and apparatus of the present invention, arranged to inject sterilized liquid in the high electric field application region formed between the electric field application electrode is confronted at required intervals, the electric field Electrons released by discharge from one electric field application electrode when the opposing spacing of the application electrodes is such that the high electric field pulse has a rise time of 100 ps to less than 20 ns, a pulse width of less than 100 ns, and a fall time of 100 ps to 100 ns or less. As a distance that does not reach the other electric field application electrode, the liquid to be sterilized in the high electric field application region has a rise time of 100 ps to less than 20 ns, a pulse width of less than 100 ns, a fall time of 100 ps to 100 ns, and Method of applying sterilization by applying a high electric field pulse with an electric field strength of 30 to 300 kV / cm, and sterilization target By disposing the pair of plate-shaped electric field applying electrodes were opposed at predetermined intervals on both sides of the space portion so as to accommodate the body, the opposed distance of the field application electrode, a high electric field pulse rise time 100ps~ When the electric field emitted from one electric field application electrode moves and does not reach the other electric field application electrode when the pulse width is less than 20 ns, the pulse width is less than 100 ns, and the fall time is 100 ps to 100 ns or less, A high electric field application region is defined between the application electrodes, and the rise time is 100 ps to less than 20 ns, the pulse width is less than 100 ns, and the fall time is 100 ps to the liquid to be sterilized which is injected and arranged in the high electric field application region. short pulse generation instrumentation for applying the following and by and high electric field pulses the field strength and 30~300kV / cm 100ns There a device including a also a high electric field region formed between the conductor made of the resonant cavity and integrally coupled to the outer periphery of the insulator made of container and the insulator made of container, at least 50MHz or higher there is irradiated with microwaves of a frequency as, for the sterilized liquid guided into the high electric field application region through the insulator steel vessel, the electric field strength by applying a high electric field pulses and 30~300kV / cm how to perform sterilization Te, and a conductor made resonant cavity outside periphery of the insulator made of container that is as a sterilized liquid can be accommodated given time to flow from one direction integrally connected, conductor A high electric field application region is formed between the resonance cavity and the insulator container , and the high electric field application region is irradiated with microwaves having a frequency of at least 50 MHz or more and is sterilized guided to the high electric field application region versus Since it is an apparatus comprising a microwave generator for applying a high electric field pulse with an electric field strength of 30 to 300 kV / cm to an elephant liquid, the electric field of the high voltage pulse applied without causing dielectric breakdown Strength can be increased, thereby applying a high electric field pulse having a higher electric field strength to the liquid to be sterilized compared to the conventional case, thereby increasing the strength of physical damage imparted to microorganisms in the liquid to be sterilized. It is possible to sterilize relatively robust spore bacteria that could not be sterilized by the conventional high electric field pulse sterilization method, and it is high even if the pulse width is shortened by increasing the electric field strength of the high electric field pulse. Since the sterilization effect can be obtained, the total time during which the electric field is applied to the liquid to be sterilized can be shortened compared to the conventional case, and the sterilization treatment can be made non-heating. Can be further it can limit the electrons and ions movements and reactions, there is exhibited an excellent effect that can be to prevent the deterioration of the sterilized liquid itself.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 shows an embodiment of a high electric field pulse sterilization method and apparatus of the present invention, in which (A) is a schematic cut front view, and (B) is an AA arrow view of (A).
FIG. 2 is a partially cut schematic perspective view showing another embodiment of the present invention.
FIG. 3 is a graph showing the relationship between the electric field intensity of the applied high electric field pulse and the survival rate of the bacteria in the high electric field pulse sterilization method.
[Explanation of symbols]
4 Electric field application electrode 5 High electric field application region 6 Short pulse generator 8 Liquid to be sterilized 11 Tube (insulator container)
15 Microwave generator 16 Microwave

Claims

The liquid to be sterilized is placed in a high electric field application region formed between the electric field application electrodes confronted with each other at a required interval, and the confrontation interval of the electric field application electrodes is set so that the rising time of the high electric field pulse is less than 100 ps to 20 ns, When the pulse width is less than 100 ns and the fall time is 100 ps to 100 ns or less, the high electric field application region is defined as a distance where electrons discharged from one electric field application electrode do not move and reach the other electric field application electrode. Is sterilized by applying a high electric field pulse with a rise time of 100 ps to less than 20 ns, a pulse width of less than 100 ns, a fall time of 100 ps to 100 ns and a field strength of 30 to 300 kV / cm. A high electric field pulse sterilization method characterized by performing.

A microwave having a frequency of at least 50 MHz is irradiated to a high electric field application region formed between the insulator container and the conductor-made resonant cavity connected to the outer periphery of the insulator container. , for the sterilized liquid guided into the high electric field application region through the insulator steel vessel, characterized in that to perform sterilization by applying a high electric field pulses the field strength and 30~300kV / cm High electric field pulse sterilization method.

A pair of flat electric field application electrodes opposed to each other at a required interval are arranged on both sides of the space where the liquid to be sterilized can be accommodated , and the high electric field pulse increases the rising time of the electric field application electrode. As a distance at which electrons emitted from one electric field application electrode move and do not reach the other electric field application electrode when the pulse width is less than 100 ns, the fall time is 100 ps to 100 ns or less when the pulse width is less than 100 ns and less than 100 ns, With respect to the liquid to be sterilized arranged between the electric field application electrodes as a high electric field application region and injected into the high electric field application region , the rise time is less than 100 ps to less than 20 ns, the pulse width is less than 100 ns, and the fall time is short pulses for the following and to and field strength 100ps~100ns applied high electric field pulses and 30~300kV / cm High electric field pulse sterilization apparatus characterized in that it comprises a generator.

The sterilized liquid flow from one direction to integrally connect the conductor made resonant cavity outside periphery of the insulator made of container that is to be able to accommodate a predetermined time, the conductor made of the resonant cavity and the insulation container made A high electric field application region is formed between the two , and a microwave having a frequency of at least 50 MHz is applied to the high electric field application region to irradiate the liquid to be sterilized led to the high electric field application region with an electric field strength of 30. A high electric field pulse sterilizer comprising a microwave generator for applying a high electric field pulse of ˜300 kV / cm .