JP3561734B2 - Method for cleaning membrane for taste sensor - Google Patents

Description

【００１０】
前記明細書にいう味覚センサは正に味覚センサであって、人の味覚器官である舌に近い物理化学的性質を持ち、呈味物質が異なっても同様な味であれば同様な出力が得られるし、異なる味に対してもなんらかの出力がえられる。色に例えてこれをいえば、カラーで検出できるセンサである。
【００１１】
この味覚センサを用いてアジを測定する方法として、本願出願人は他と共同して、「アジ検出方法」（特開平４−０６４０５３号）を特許出願した。この発明によりビール等の食品の銘柄差やロット差等の微細なアジの差まで識別可能となった。概略を以下に述べる。
脂質性分子を用いた味覚センサによるアジの検出、測定を再現性よく行うために、基準液として被測定サンプル液に近いものを用いることとし、味覚センサを基準液に十分に浸漬することとし、味覚センサに測定ごとに同様な刺激を加えることとし、測定時刻を表面電位の安定後であって内部電位が緩慢に変化する時に選ぶこことし、基準液と被測定サンプル液の測定値の差を計算することとした。測定対象がビールならビールまたはビールに近いアジの物を基準液とし、センサを予め前記基準液に漬けて、センサを前記基準液になじませておく。これにより、ビール中に含有する脂質膜に吸着性のある物質を予め吸着させておいて、各種のビールを測定した時、吸着性物質の影響を少なくするものである。脂質膜に吸着した物質に対する感度は低くなるものの、再現性が非常に向上する効果がある。
【００１２】
また、本願出願人の一部は上記「アジ検出方法」をより進めた検出方法として「アジの検出方法」（特願平４−３４９６８８）を特許出願した。
この中の第１の発明のアジの検出方法によれば、両親媒性物質または苦味物質の分子膜（以後、分子膜と略記する）を用いた味覚センサによるアジの検出、測定を再現性よく行うために、第一の基準液及び第二の基準液としてサンプル液と近いものを用いることとし、第一の基準液（Ｖ０ ）→第二の基準液（Ｖｋ ）→第一の基準液（Ｖ０ ´）→サンプル液（Ｖｓ ）の順に測定しサンプル液測定値の基準値からの相対値｛（Ｖｓ −Ｖ０ ´）−（Ｖｋ −Ｖ０ ）｝を計算することにより味覚センサの継続的なドリフトにおける相対値のばらつきを無くし、第一の基準液を用いることによって第一の基準液の味が変化しても測定値への影響を無くした。
【００１３】
つぎに、センサの洗浄について述べる。
味覚センサと同じように、被測定溶液に浸けて、該溶液に含まれる物質についての測定を行うセンサには、半導体センサ、イオンセンサ等があるが、半導体センサ等の、表面が金属のセンサ以外のセンサでは、洗浄ということは行われていない。
半導体センサは、表面が金属であるため、エタノール等の有機溶剤にも強く、洗浄によるセンサの特性変化が無い。
イオンセンサにおいては、サンプルを測った結果、センサ表面が汚れた場合でも、純水にて軽くすすぐ程度で十分であり洗浄の必要性が余り無かった。理由の１つには、測定対象はイオンであり、センサへの吸着性が低く、洗浄の必要が無いことが挙げられる。理由のもう一つは、高選択性であることが挙げられる。イオンセンサは、１つの化学物質を精度よく測ることが目的であり、対象の化学物質に対する選択性が高い。また、対象物質以外への感度を持っている場合でも、サンプルを処理して、それら妨害イオンの影響を無視できるような測定方法を取っている。つまり、１つの対象物質の感度のみが分かっていれば良い。汚染に依って測定対象に対する感度が変化しても、つねに校正液にて検量線を引いて感度を校正して使用するため、洗浄する必要が無い。
【００１４】
分子膜を用いた味覚センサもその一つであるが有機材料から出来ているセンサにおいては、洗浄することで、膜が破壊され、大きく特性が変わり、洗浄は無理と考えられていた。
分子膜を用いた味覚センサの場合、測定対象の味物質には、吸着性の強い、苦味物質、旨味、渋味、油性のもの他が当然含まれ、サンプルを測ることで、膜への吸着による膜の特性変化は避けられない。人の場合も、ブラックコーヒーを飲む前後で、苦味物質が舌に残るため、味覚特性が変化する。また、分子膜を用いた味覚センサでは、イオンセンサと異なり、人の舌と同様、反応する呈味物質の種類が莫大にあり、それら１つ１つの対象の呈味物質の感度を測って校正することは、非常に難しい。これらより、分子膜を用いた味覚センサの場合、洗浄の必要性は大いにあった。しかし、脂質自体が有機材料であるため、洗浄により膜が破壊され、特性が大きく変化すると考えられ、洗浄は困難とされていた。
【００１５】
そこで、従来は、分子膜を用いた味覚センサで分子膜に吸着する物質を含む被測定サンプル液の測定を行う場合、前述のように、被測定溶液の測定を行う前に、基準液として被測定サンプル液と近いものを用意し、味覚センサを基準液に十分に浸漬して、基準液中の分子膜に吸着する物質を予め吸着させて、測定時の吸着物質の影響を少なく（安定化）していた。
【００１６】
【発明が解決しようとする課題】
従来技術では、分子膜を用いた味覚センサの洗浄ができなかったので、再現性を良くするために（安定化させるために）、基準液として被測定サンプル液に近いものを用いることとし、測定の前段階として味覚センサを基準液に十分に浸漬し、膜（分子膜）に吸着する物質は予め吸着させてから測定を行うようにしていた。そのために、次のような問題があった。
▲１▼情報量が少ない。
味覚センサは基準液中の様々な呈味物質をある程度吸着させることにより安定している。したがって、苦味等の吸着性の大きい呈味物質に関する感度が低くなり、アジの情報量が少なくなる。
【００１７】
▲２▼基準液の合成が難しい。
従来は味覚センサの校正に使う基準液に実際の食品を用いていたので、基準液自体にロット間の差や経時変化がありデータの一貫性に問題があった。そこで、常に一定の成分比で経時変化のない基準液の合成が求められた。前記「アジ検出方法」のような測定方法を取る場合、測定対象の食品中に含まれる膜への吸着性のある物質を全て含む基準液に漬けて、センサ表面に十分吸着させる必要があった。吸着性のある物質Ａがその基準液に含まれていない場合、物質Ａを含む被測定溶液を測定したとき、膜に物質Ａが吸着して特性が変化し、安定した測定が出来ない。したがって、基準液は吸着物質を網羅しなければならない。しかし、食品中には脂質膜へ吸着する物質の種類は多く、それらを網羅することは、わずらわしく、食品工場などでその場の作業員にそれぞれが対応をとれるように教育することは事実上困難である。
【００１８】
▲３▼同一のセンサで安定して測定できる範囲が狭い。
これは、特に工場廃液等の汚染物質を測る際に問題である。味覚センサを用いて工場廃液をチェックする場合を考えると、工場廃液には多種類の物質が含まれており、これらの物質が膜に吸着すると、その前後で膜の特性が変わり、もとに戻すのに、長い時間がかかる。事前に廃液に含まれる吸着物質の種類が決まっていれば、その廃液に応じた基準液を作り、センサをなじませておくことが可能であるが、現実には、予期しない物質が排出される可能性が大きい。また、工場廃液等の測定では、特に予期しない物質の検知も重要である。
【００１９】
前述の問題点はいずれも膜への吸着物質を洗浄することができないことから生じている。
この発明の目的は、上記問題点、すなわち、▲１▼情報量が少ない、▲２▼基準液の合成が困難、▲３▼同一のセンサで安定して測定できる範囲が狭い、等の問題を解決するために、味覚センサ用膜の洗浄方法を提供することである。
【００２０】
【課題を解決するための手段】
発明者等は、味覚センサ用膜の洗浄方法について、種々の検討、実験を行い、洗浄により膜が破壊されると考えられていた有機溶剤も希釈したものを用いれば洗浄液として使用できることを見出した。また、表６にその一部が挙げてあるが、味覚センサ用膜は、人の味覚を再現できるような多くの味覚情報を得るために、それぞれ味に対して異なる応答特性を持つものが必要であり、多種類のものがある。中には有機溶剤だけでは十分な洗浄ができないものがあるが、それらに対しては希釈した有機溶剤に酸、塩、アルカリ等の電解質を加えたものが効果的であることを見出した。さらに、ニガリ等が吸着している場合には酸の希釈液が有効であることを見出した。
すなわち、第１の発明では、有機溶剤の希釈液を用いて洗浄を行うこととした。また、第２の発明では、有機溶剤の希釈液に電解質を加えたものを用いて洗浄を行うこととした。さらに、第３、第４、第５、第６の発明では、前記電解質としてそれぞれ酸、塩、酸および塩、アルカリを加えたものを用いて洗浄を行うこととした。そして、第７の発明では、酸の希釈液を用いて洗浄を行うこととした。
【００２１】
【作用】
この発明が採用する各種の洗浄液が有効なセンサ膜について概説する。
１．有機溶剤はほぼ全てのセンサ膜に有効であり、吸着性物質の中で疎水性が強く膜の疎水性部位に吸着するものを有機溶剤の疎水性を利用して洗浄を行う。
２．酸は、リン脂質等のマイナス荷電を帯びた脂質の膜に特に有効であり、吸着性物質の中で、プラスに荷電し脂質のマイナスの官能基と化学反応して塩になるものを、酸の水素イオンの置換作用を利用して行う。その後、基準液での共洗い又は基準液での安定化により水素イオンを離し（脂質の官能基の解離）、元の状態にさせる。この時、酸での洗浄の後に中性または弱アルカリでの簡単なすすぎにより余分な水素イオンを早く離して測定のスピードアップが図れる。この酸の作用は塩化ナトリウムや塩化カリウム等の塩でも考えられるが、ナトリウムイオンやカリウムイオンの置換作用は水素イオンの約１／１００であり、上記の作用に関してはあまり効果が期待できない。
【００２２】
３．塩は、アンモニューム基等のプラス電荷を帯びる基を持つ脂質に特に有効であり、吸着性物質の中で、マイナスに荷電し脂質のプラスの官能基と化学反応して塩になるものを塩の塩素イオン等のマイナスイオンの置換作用を利用して行う。その後、基準液での共洗い又は基準液での安定化により塩素イオンを離し（脂質の官能基の解離）、元の状態にさせる。この時、塩での洗浄の後に純水の簡単なすすぎにより余分な塩素イオンを早く離して測定のスピードアップが図れる。この塩の作用は塩酸等の酸でも考えられるが、マイナスイオンである塩素イオンの濃度を高濃度にしないと置換効果がないため、酸も高濃度が必要であり、実質上扱いが難しい。
【００２３】
４．アルカリは、アンモニューム基を持つ脂質に特に有効である。アンモニューム基はアンモニューム基に水素イオンが配位結合し、その水素イオン部分にマイナスに荷電した吸着性物質が化学反応して塩になって結合している。そこで、アルカリになるとアンモニューム基と水素イオンの配位結合がはずれ、その結果水素イオンといっしょに吸着物質もはずれる。この作用を利用して洗浄を行う。その後、基準液での共洗いまたは基準液での安定化により水素イオンをアンモニューム基と配位結合させて、元の状態にさせる。この時、アルカリでの洗浄の後に酸での簡単なすすぎにより水素イオンを早く配位結合させて測定のスピードアップが図れる。
【００２４】
５．また、同じ種類の膜でもそれに吸着する物質の種類によっては効果のある洗浄液が多少異なるものもある。例えば、家庭塩や天塩と言った”しお”のように無機イオンだけの場合、その苦味の成分のカルシウムやマグネシウムの洗浄では酸のみで効果がある。
これらを請求項毎に表１にまとめる。
【００２５】
【表１】

【００２６】
表１で数字は表２に挙げる分子膜の種類を示す。また、表１から分かるように同じ分子膜でも複数種類の洗浄液が有効なものもある。（ ）付きのものは（
）のないものより多少効果が落ちるが、例えば同じ洗浄液を用いて洗浄してしまいたいときなど適用できる。
【００２７】
【表２】

【００２８】
【実施例】
以下、本発明の実施例を説明する。
第１の実施例は、洗浄液としてエタノールの３０％水溶液を用いた。
第２の実施例は、エタノールの３０％水溶液であり、かつ、塩酸１００ｍＭ（ｍ ｍｏｌｅ）水溶液であるものを洗浄液として用いた。
第３の実施例は、エタノールの３０％水溶液であり、かつ、塩化ナトリウム２Ｍ（ｍｏｌｅ）水溶液であるものを洗浄液として用いた。
第４の実施例は、エタノールの３０％水溶液であり、塩酸１００ｍＭ水溶液であり、かつ、塩化ナトリウム２Ｍ水溶液であるものを洗浄液として用いた。
第５の実施例は、エタノールの３０％水溶液であり、かつ、水酸化ナトリウム１０ｍＭ水溶液であるものを洗浄液として用いた。
第６の実施例は、洗浄液として塩酸１００ｍＭ水溶液を用いた。
前掲の表１は第１〜第６の実施例の洗浄を行ったことによる効果を確認するための実験の結果を示す表でもある。
【００２９】
表１において、左欄の請求項１に対応する実施例は第１の実施例、請求項３に対応する実施例は第２の実施例、請求項４に対応する実施例は第３の実施例、請求項５に対応する実施例は第４の実施例、請求項６に対応する実施例は第５の実施例、請求項７に対応する実施例は第６の実施例である。上欄は被測定溶液（吸着物質を含んだ溶液）を表し、他の欄はそれぞれ対応する被測定溶液を測定したときに吸着した物質を該当する実施例の洗浄液で洗浄して効果のあった膜の種類を示す。
測定は後述する第１のアジの検出方法（図１）によった。５回繰り返してその測定値の標準偏差より効果を判断した。
【００３０】
この結果から、大部分の分子膜および大部分の被測定溶液には第１の実施例の洗浄が有効であることが分かる。だから、大部分の吸着物質は膜の疏水性部位に吸着していると考えられる。また、第１の実施例の洗浄でも効果がない場合は第２の実施例の洗浄が有効であり、特に、表２のＮｏ． １の分子膜（ジオクチルフォスフェート）の官能基はＰＯＯＨでマイナス膜であり作用の欄の２．で述べた効果である。この２つの実施例で全体の９０％についての洗浄は行える。特に、日本酒およびビールの場合、全ての分子膜の洗浄ができる。
実施例では、有機溶剤としてエタノールを用いた。メタノールやアセトン等も有効であるが、味覚センサは主に飲食物を測定対象としているために無毒であるエタノールが適している。
【００３１】
以上のように、味覚センサの洗浄が可能となったことから、アジの検出方法も従来の技術の欄で概略のべた方法とは異なる方法が採れることとなった。
図１は、本発明の洗浄方法をその一部に用いた第１のアジ検出方法のアルゴリズムである。詳しくは、以下に述べる。
１）基準液Ａにて、脂質膜を用いた味覚センサを数時間程度浸ける。基準液Ａは、塩と酸および洗浄作用を持つ化学物質からなる。つまり、センサの校正を行う作用と洗浄作用を兼ねている。基準液Ａは、脂質膜への吸着性の少ない塩と酸から作製すると吸着物質への感度向上効果が大きい。
２）基準液Ａのセンサ電位を測定する。
３）バッチ式測定（被測定溶液を例えばビーカ等に採って行う測定の方式）の場合、味覚センサを空中に一定回数出し入れした後、再度基準液Ａのセンサ電位を測定する。フロー式測定（例えば、味覚センサのセットされた測定用のパイプに被測定溶液および基準液をそれぞれ流して行う測定の方式）の場合、味覚センサに基準液Ａを一定時間流した後、再度基準液Ａのセンサ電位を測定する。
４）一回前に測定して基準液Ａのセンサ電位と比較して、変化の幅が設定値以内に収まっていれば、安定したとみなし、５）へ進みサンプルのセンサ電位を測定する。変化幅が設定値以上であった場合、３）に戻る。この意味は、２つある。１つは、従来技術で述べたようにセンサの出し入れや測定液のフローの影響をチェックし、影響がなくなるまでセンサの出し入れや測定液のフローの操作を周期的に行うものである。もう１つは、洗浄液により、膜表面がリフレッシュされて一定な状態になったかどうかのチェックを行うものである。最終的に安定した基準液のセンサ電位をＶＡ とする。
５）センサが安定した所で、サンプル（被測定溶液）Ｓｉ のセンサ出力（Ｖｉ ）を測る。
６）サンプルＳｉ の測定結果△Ｖｉ ＝Ｖｉ −ＶＡ を算出する。
７）連続してサンプルを測定する場合は２）へ進む。
【００３２】
第１のアジ検出方法は、基準液Ａ自体がセンサの洗浄液を兼ねていたが、図２に示す第２のアジ検出方法では、別に洗浄液を設けた測定方法を示す。
この場合の基準液Ａは、第１のアジ検出方法のように洗浄のための物質を含む必要がない。サンプルを測定した後、センサに吸着した物質の洗浄処理を行う。具体的な洗浄処理としては、例えばバッチ式の場合は、洗浄液にセンサを浸漬して動かす、あるいは洗浄液にセンサを出し入れする、等である。
【００３３】
第２のアジ検出方法では、基準液Ａを脂質膜への吸着性の少ない物質で合成してそれらの物質への感度向上を図っていたが、図３に示す第３のアジ検出方法では、吸着性物質を含む測定対象に近いものもしくは、測定対象そのものを使用する場合の測定方法を示す。この場合、基準液自体に膜への吸着性物質が含まれるため、基準液の測定後にも洗浄処理を行う。
【００３４】
第１〜第３のアジ検出方法は、基準液Ａを、センサ電位の校正という言葉本来の意味の他に、センサの出し入れやフローの影響を除く操作（安定化）にも使用していたが、図４〜６に示す第４〜第６のアジ検出方法は、従来技術に述べたような、安定化のための基準液Ａとセンサ電位の校正のための基準液Ｂの２種類を使用する場合の測定方法を示す。
【００３５】
第４のアジ検出方法（図４）は、第１のアジ検出方法と同様に基準液Ａが洗浄のための物質を含む測定方法である。基準液Ａの内容は、第１のアジ検出方法の場合と同様である。基準液Ｂの内容は第２のアジ検出方法の基準液Ａと同様である。
第５のアジ検出方法（図５）は、洗浄処理をサンプル測定後に行う測定方法である。基準液Ａ、Ｂの内容は第２のアジ検出方法の基準液Ａと同様である。
第６のアジ検出方法（図６）は、センサの校正用基準液Ｂに第３のアジ検出方法の基準液Ａと同様である。
【００３６】
以上述べた検出方法では、以下の処理を行う場合がある。
▲１▼基準液Ａでのセンサの安定性チェックは、数サンプルに１回行ってもよい。
▲２▼基準液Ａでのセンサの安定性チェックにおいて、安定が悪い場合洗浄処理に戻ってもよい（第２のアジ検出方法、第３のアジ検出方法、第５のアジ検出方法、第６のアジ検出方法）。
▲３▼サンプル、基準液Ａ、基準液Ｂの測定前に各々の液で共洗いを行ってもよい。この場合、第１のアジ検出方法および第４のアジ検出方法では、基準液Ａに洗浄のための物質が含まれるため、共洗い自体が、洗浄処理となる。
▲４▼センサの種類や吸着物質の種類により、洗浄方法は異なるため、別々の洗浄処理を行う場合がある。洗浄処理が、いろいろな洗浄処理の組み合わせとなる場合がある。
【００３７】
分子膜を用いた味覚センサを使用し、国産ビール１４銘柄と国産インスタントコーヒー１２種について、本発明の洗浄方法を用いたアジ検出方法による情報量の増加の例を示す。従来方法は、味覚センサを事前にビールに数日漬けて安定化してあるもので、測定手順は前記第１のアジ検出方法とほぼ同じである（但し、基準液は実際のビールを使用）。本発明の洗浄方法を用いたアジ検出方法は、前記第１のアジ検出方法である。測定結果の主成分分析結果を図７〜図１０に示す。図７は、本発明の洗浄方法を適用した検出方法によるビールの主成分分析結果で、図８は従来方法によるビールの主成分分析結果である。図９は、本発明の洗浄方法を適用した検出方法によるコーヒーの主成分分析結果で、図１０は従来方法によるコーヒーの主成分分析結果である。従来方法では、第一主成分の寄与率がビールの場合８６．９％、コーヒーの場合９２．０％で第一主成分が大部分でほぼ１次元の情報しかないが、本発明の洗浄方法を適用した検出方法では、第一主成分と第二主成分が直交し、２次元プラスアルファの情報を得ている。
実際の運用としては、従来の検出方法と本発明の洗浄方法を適用した検出方法の兼用も考えられる。例えば、コーヒーの場合、Ｎｏ．３の膜を用いて従来の検出方法と本発明の洗浄方法を適用した検出方法の両方の結果を用いれば、Ｎｏ．３の膜のみで直行した２次元情報を得ることができる。
【００３８】
エタノールの希釈液での洗浄の効果の例を述べる。
分子膜を用いた味覚センサを使用し、河川の汚水、コーヒー、ビールについて、基準液を簡単な塩と酸とで合成して測定を行った場合でも、再現性の良いことを示す。前記洗浄液と基準液を同一の液で済ました。吸着物質除去の効果をみるため塩と酸のみの基準液Ａ１（３０ｍＭ塩化カリウムと３ｍＭ塩酸）と、基準液Ａ１にエタノール３０％添加した基準液Ａ２の場合を比較した。測定手順は前記第１のアジ検出方法とほぼ同じである。但し、サンプルから基準液の測定に移る前に基準液と同じ成分の液で共洗いを実施した。結果を表３〜表５に示す。表３は河川の汚水、表４はコーヒー、表５はビールを測定した結果である。
【００３９】
【表３】

【００４０】
【表４】

【００４１】
【表５】

【００４２】
繰り返し測定誤差（標準偏差）は、エタノール添加の基準液Ａ２の方がエタノール無添加の基準液Ａ１に比べ表２に挙げたＮｏ．１、Ｎｏ．５、Ｎｏ．６の膜を除いて約１／５〜１／１０になっていてエタノールの洗浄効果が表れている。なお、Ｎｏ．１、Ｎｏ．５、Ｎｏ．６の膜においても、前記第２〜第４の実施例の洗浄を行うことで測定誤差は他の膜と同様に著しく良くなる。
【００４３】
日本酒の場合、３ｍＭこはく酸、３０ｍＭ塩化ナトリウム、かつ４０％エタノールである混合液を洗浄液に、３ｍＭこはく酸、３０ｍＭ塩化ナトリウム、かつ１５％エタノールである混合液を基準液として用いた。測定誤差は約０．２ｍＶ以下であり、日本酒の幅が３０〜４０ｍＶなので、誤差率は１％以下であり非常に高精度である。
【００４４】
【発明の効果】
第１の発明では、有機溶剤の希釈液を用いて洗浄を行うこととし、第２の発明では、有機溶剤の希釈液に電解質を加えたものを用いて洗浄を行うこととし、第３、第４、第５、第６の発明では、前記電解質としてそれぞれ酸、塩、酸および塩、アルカリを加えたものを用いて洗浄を行うこととし、第７の発明では、酸の希釈液を用いて洗浄を行うこととしたから、
従来技術では困難であった味覚センサ用膜の洗浄が可能となった。
また、膜の洗浄が可能となったことによって、以下に述べる効果もある。
すなわち、
▲１▼苦味等の分子膜への吸着物質への味覚センサの感度が向上したことで、味に関する情報量が増加した。
▲２▼基準液の合成が容易になり、データの再現性が向上した。（塩と酸の単純な合成基準液でも再現性よく測定できるようになった。）
▲３▼測定対象の範囲が広くなった。
【図面の簡単な説明】
【図１】本発明の洗浄方法を利用した第１のアジ検出方法を示す流れ図である。
【図２】本発明の洗浄方法を利用した第２のアジ検出方法を示す流れ図である。
【図３】本発明の洗浄方法を利用した第３のアジ検出方法を示す流れ図である。
【図４】本発明の洗浄方法を利用した第４のアジ検出方法を示す流れ図である。
【図５】本発明の洗浄方法を利用した第５のアジ検出方法を示す流れ図である。
【図６】本発明の洗浄方法を利用した第６のアジ検出方法を示す流れ図である。
【図７】本発明の洗浄方法を利用した第１のアジ検出方法でビールを測定した結果を主成分分析した結果を示す図であり、（ａ）は第１主成分と第２主成分とで表した図、（ｂ）は第１主成分と第３主成分とで表した図である。
【図８】従来のアジ検出方法でビールを測定した結果を主成分分析した結果を示す、第１主成分と第２主成分とで表した図である。
【図９】本発明の洗浄方法を利用した第１のアジ検出方法でコーヒーを測定した結果を主成分分析した結果を示す図であり、（ａ）は第１主成分と第２主成分とで表した図、（ｂ）は第１主成分と第３主成分とで表した図である。
【図１０】従来のアジ検出方法でコーヒーを測定した結果を主成分分析した結果を示す、第１主成分と第２主成分とで表した図である。
【図１１】脂質膜を化学物の設計法で使われている表現方法で表した模式図である。
【図１２】味覚センサの模式図であり、（ａ） は正面図、（ｂ） は断面図である。
【図１３】アジの測定系を示す図である。
【符号の説明】
１ 基材（基板）
２ 電極
３ 脂質膜
４ 緩衝層
５ リード線
１１ 被測定溶液
１２ 容器
１３ 味覚センサアレイ
１４ 各々の脂質膜（黒点で示す）
１５ 参照電極
１６ 緩衝層
１７ リード線
１８ リード線
１９ バッファ増幅器
２０ アナログスイッチ
２１ Ａ／Ｄ変換器
２２ マイクロコンピュータ
２３ Ｘ−Ｙレコーダ
３１ 脂質性分子群
３１’脂質性分子群
３２ 膜部材
３３ マトリックス[0001]
[Industrial applications]
The present invention relates to a method for cleaning a membrane used for a sensor capable of detecting and measuring a difference in taste of food and drink, that is, a sensor capable of acting as a substitute for taste, which is one of the five senses of humans, And a cleaning method capable of removing substances adsorbed on the membrane from the membrane.
[0002]
[Definition of terms]
It is said that there are saltiness, sweetness, bitterness, sourness, and umami as basic elements of taste, and each has a degree of magnitude. The difference in taste that can be evaluated by human senses, or the difference in taste (of the same kind) for salty taste, if salty, can be grasped as a physically measurable quantity, and the difference in measurable taste or taste (Comparative or contrasting taste) will be referred to herein as “adzuki”.
In addition, during the operation of washing out substances contained in the solution to be measured attached to the taste sensor, in order to prevent contamination of the solution to be measured next to be measured by another solution to be measured, when the taste sensor is immersed in the solution, An operation that includes the removal of substances adsorbed on lipid membranes is called `` washing '', in contrast to an operation called `` co-washing '', which is used to wash off objects that are easily attached. And
Adsorption may be divided into physical adsorption and chemical adsorption in lectures, but the forces acting between atoms or between molecules are variously used along with the combination of mutual atoms and molecules, and the definition of "adsorption" is difficult, Here, all the ways of attachment that cannot be removed by the above “co-washing” are included.
[0003]
[Prior art]
First, a technique for measuring horse mackerel will be described.
As a technique for measuring horse mackerel, for example, as disclosed in Japanese Patent Application Laid-Open No. 62-187252, each original taste (basic taste) component in a measurement object, that is, a substance from which a selected taste is derived, from output values of a plurality of taste sensors. (E.g., salt, sucrose, quinine, acetic acid, glutamate, etc.) That is, by calculating the concentration of the taste substance and correcting each concentration value to a value representing the strength of each taste corresponding to the taste of human. Some measure horse mackerel.
However, the taste sensor referred to in the above publication is a chemical sensor or a physical sensor that selectively detects a substance exhibiting each basic taste. Specifically, salty taste is measured with a salt concentration meter, sourness is measured with a hydrogen ion index meter, and sweetness is measured. Was a refractometer using the refractive index of the liquid to be measured. Since these sensors are selective, for example, a salt concentration meter that is trying to measure the strength of salty taste can measure the concentration of salt, but cannot measure the concentration of other substances that exhibit salty taste, and it suits human taste There was a limit to the correction. Speaking of color, it is like trying to get a color result using a sensor that only detects a single color.
[0004]
The present applicant has jointly filed a patent application (Japanese Patent Application No. 1-190819) for "taste sensor and method for producing the same" with others, and has described a hydrophobic part and a hydrophilic part in the specification and drawings. A lipid molecular film having a structure in which a lipid substance composed of a molecule having the following structure is fixed in a polymer matrix, and the hydrophilic portion of the lipid molecule is aligned on the surface of the lipid substance, is a sensor for horse mackerel, that is, a human sensor. It was shown that it could be a taste sensor that could replace the taste.
[0005]
FIG. 11 shows the membrane diagram of the lipidic molecular membrane expressed by the expression method used in the method of designing a chemical substance. The globular part shown by a circle in the lipid molecule is a hydrophilic group a, that is, a hydrophilic site a, and there is a hydrocarbon chain structure b (for example, an alkyl group) whose atomic arrangement extends for a long time. In each case, two chains are extended to represent one molecule in each case, and the whole constitutes a molecule group. This part of the hydrocarbon chain is the hydrophobic site b. Such a lipid molecule group 31 is partially dissolved in the matrix 33 (surface structure, microstructure having planar spread) on the surface of the membrane member 32 (for example, 11 ') in FIG. The accommodation is such that hydrophilic sites are arranged on the surface.
[0006]
FIGS. 12A and 12B show a multi-channel taste sensor using this lipid molecular membrane. In this figure, three sensitive parts of the multi-channel array electrode are shown.
In the illustrated example, a 0.5 mmφ hole was penetrated through the substrate, and a silver round bar was inserted into the hole to form an electrode. The lipid molecular membrane is adhered to the substrate via the buffer layer so as to contact the electrode.
[0007]
FIG. 13 shows a horse mackerel measurement system using the multi-channel taste sensor.
An aqueous solution of the taste substance is prepared, and it is used as a solution to be measured 11 and placed in a container 12 such as a beaker. The taste sensor array 13 formed by arranging a lipid membrane and electrodes on an acrylic plate (substrate) as described above was placed in the solution to be measured. Prior to use, the electrode potential was stabilized with a 1 mmol / l aqueous solution of potassium chloride. In the drawing, 14-1,..., 14-8 indicate the respective lipid membranes by black dots.
A reference electrode 15 is prepared as an electrode for generating a potential serving as a measurement reference, and is placed in the solution to be measured. The taste sensor array 13 and the reference electrode 15 are installed at a predetermined distance. Since the surface of the reference electrode 15 is covered with a buffer layer 16 coated with 100 mMole / l of potassium chloride solidified with agar, the electrode system is eventually composed of silver 2 | silver chloride 4 | lipid membrane 3 (14) | The solution to be measured 12 | buffer layer (potassium chloride 100 mmol / l) 16 | silver chloride 4 | silver 2
[0008]
The electrical signal from the lipid membrane becomes an eight-channel signal in the figure, and is led to buffer amplifiers 19-1,..., 19-8 by leads 17-1,. Each output of the buffer amplifier 19 is selected by an analog switch (8 channels) 20 and applied to an A / D converter 21. The electric signal from the reference electrode 15 is also applied to the A / D converter 21 via the lead 18 and converts the difference from the potential from the membrane into a digital signal. This digital signal is appropriately processed by the microcomputer 22 and displayed by the XY recorder 23.
In this example, an 8-channel taste sensor is used, and each channel has a different response characteristic to taste in order to obtain a lot of taste information that can reproduce human taste. It is composed of a molecular film.
[0009]
[Table 6]

[0010]
The taste sensor referred to in the above specification is exactly a taste sensor, which has physicochemical properties close to the tongue which is a human taste organ, and a similar output can be obtained even if the taste substance is different if the taste is similar. And some output for different flavors. Speaking of color, this is a sensor that can detect color.
[0011]
As a method for measuring horse mackerel using this taste sensor, the applicant of the present application has filed a patent application for a Japanese horse mackerel detection method (Japanese Patent Application Laid-Open No. 4-064053) in collaboration with others. According to the present invention, it is possible to identify even small differences in horse mackerel such as brand differences and lot differences of foods such as beer. The outline is described below.
In order to perform the detection and measurement of horse mackerel with a taste sensor using lipidic molecules with good reproducibility, a reference solution close to the sample solution to be measured shall be used, and the taste sensor shall be sufficiently immersed in the reference solution, A similar stimulus is applied to the taste sensor for each measurement, and the measurement time is selected when the surface potential is stable and the internal potential changes slowly, and the difference between the measured values of the reference solution and the sample solution is measured. It was decided to calculate. If the object to be measured is beer, beer or a horse mackerel close to beer is used as a reference liquid, a sensor is pre-soaked in the reference liquid, and the sensor is adapted to the reference liquid. Thus, the effect of the adsorptive substance is reduced when various kinds of beers are measured by previously adsorbing the adsorbable substance to the lipid membrane contained in the beer. Although the sensitivity to the substance adsorbed on the lipid membrane is reduced, the reproducibility is greatly improved.
[0012]
In addition, a part of the applicant of the present application has filed a patent application for a "method for detecting horse mackerel" (Japanese Patent Application No. 4-349688) as a detection method which is an advanced version of the above-mentioned "magnet detection method".
According to the method of detecting horse mackerel according to the first aspect of the present invention, detection and measurement of horse mackerel by a taste sensor using a molecular film of an amphipathic substance or a bitter substance (hereinafter abbreviated as molecular film) are performed with good reproducibility. For this purpose, the first reference liquid and the second reference liquid that are close to the sample liquid are used, and the first reference liquid (V0) → the second reference liquid (Vk) → the first reference liquid ( V0 ′) → sample liquid (Vs) in order and calculate the relative value {(Vs−V0 ′) − (Vk−V0)} of the measured value of the sample liquid from the reference value to continuously drift the taste sensor. And the use of the first reference liquid did not affect the measured value even if the taste of the first reference liquid changed.
[0013]
Next, cleaning of the sensor will be described.
As with the taste sensor, sensors that are immersed in the solution to be measured and measure substances contained in the solution include semiconductor sensors and ion sensors. No cleaning is performed in the sensor of the above.
Since the surface of the semiconductor sensor is made of metal, it is resistant to organic solvents such as ethanol, and there is no change in sensor characteristics due to cleaning.
In the case of the ion sensor, as a result of measuring the sample, even if the sensor surface becomes dirty, it was sufficient to rinse the surface with pure water lightly, and there was no need for cleaning. One of the reasons is that the object to be measured is ions, the adsorptivity to the sensor is low, and there is no need for cleaning. Another reason is high selectivity. The purpose of an ion sensor is to accurately measure one chemical substance, and has high selectivity for a target chemical substance. In addition, even when the sample has sensitivity to substances other than the target substance, the sample is processed and a measurement method is used in which the influence of these interfering ions can be ignored. That is, only the sensitivity of one target substance needs to be known. Even if the sensitivity to the measurement object changes due to contamination, it is not necessary to wash because the sensitivity is always calibrated by drawing a calibration curve with a calibration solution and used.
[0014]
A taste sensor using a molecular film is one of them, but in the case of a sensor made of an organic material, the film is destroyed by washing, and the characteristics are greatly changed, and it was considered impossible to wash.
In the case of a taste sensor using a molecular film, the taste substance to be measured includes a strong adsorbent, bitter substance, umami, astringency, oily substance, etc. It is inevitable that the characteristics of the film will change. Even in the case of humans, the bitter substance remains on the tongue before and after drinking black coffee, so that the taste characteristics change. In addition, unlike ion sensors, taste sensors using molecular membranes have a huge variety of taste substances that react like human tongues. Calibration is performed by measuring the sensitivity of each target taste substance. It is very difficult to do. From these, in the case of the taste sensor using a molecular film, there was a great need for cleaning. However, since lipid itself is an organic material, it is considered that the membrane is destroyed by washing and the properties are greatly changed, and washing has been considered difficult.
[0015]
Therefore, conventionally, when a sample sensor solution containing a substance adsorbed on a molecular film is measured by a taste sensor using a molecular film, as described above, the measurement is performed as a reference solution before the measurement of the solution to be measured. Prepare a sample that is close to the sample solution to be measured, immerse the taste sensor in the reference solution sufficiently, and pre-adsorb the substance adsorbed to the molecular film in the reference solution to reduce the influence of the adsorbed substance during measurement (stabilization). )Was.
[0016]
[Problems to be solved by the invention]
In the prior art, the taste sensor using a molecular film could not be washed, so in order to improve reproducibility (to stabilize), a reference solution close to the sample liquid to be measured was used. As a pre-stage, the taste sensor was sufficiently immersed in a reference solution, and the substance adsorbed on the film (molecular film) was adsorbed in advance before measurement. Therefore, there were the following problems.
(1) The amount of information is small.
The taste sensor is stabilized by adsorbing various taste substances in the reference liquid to some extent. Therefore, the sensitivity of the taste substance having a high adsorptivity such as bitterness decreases, and the information amount of horse mackerel decreases.
[0017]
(2) It is difficult to synthesize a reference solution.
Conventionally, actual food was used as a reference solution used for calibration of the taste sensor, so that there was a difference between lots and a change with time in the reference solution itself, and there was a problem in data consistency. Therefore, it has been required to synthesize a reference solution having a constant component ratio and no change over time. When a measurement method such as the above-mentioned "fish detection method" is used, it is necessary to immerse the sensor in a reference solution containing all substances having an adsorptivity to a film contained in a food to be measured, and to sufficiently adsorb it on the sensor surface. . When the substance A having the adsorptivity is not included in the reference liquid, when the solution to be measured containing the substance A is measured, the characteristic is changed due to the adsorption of the substance A on the membrane, and stable measurement cannot be performed. Therefore, the reference liquid must cover the adsorbed substances. However, there are many types of substances that adsorb to lipid membranes in foods, and it is troublesome to cover them, and it is practically difficult to educate workers on the spot so that they can respond at food factories etc. It is.
[0018]
(3) The range in which the same sensor can measure stably is narrow.
This is a problem particularly when measuring pollutants such as factory effluents. Considering the case where factory wastewater is checked using a taste sensor, factory wastewater contains many kinds of substances, and when these substances are adsorbed on the membrane, the characteristics of the membrane change before and after that, It takes a long time to return. If the type of adsorbed substance contained in the waste liquid is determined in advance, it is possible to create a reference liquid corresponding to the waste liquid and allow the sensor to adapt, but in reality, unexpected substances are discharged The possibility is great. In the measurement of factory waste liquid, it is particularly important to detect unexpected substances.
[0019]
All of the above problems arise from the inability to wash the adsorbed material on the membrane.
An object of the present invention is to solve the above problems, namely, (1) a small amount of information, (2) difficulty in synthesizing a reference solution, and (3) a narrow range in which the same sensor can measure stably. An object of the present invention is to provide a method for cleaning a taste sensor membrane.
[0020]
[Means for Solving the Problems]
The inventors conducted various studies and experiments on a method of cleaning a film for a taste sensor, and found that a diluted organic solvent that was considered to be destroyed by cleaning can be used as a cleaning liquid. . Table 6 shows some of them, but in order to obtain a lot of taste information that can reproduce human taste, it is necessary for the taste sensor membrane to have different response characteristics to each taste. And there are many types. Although some of them cannot be sufficiently washed with only an organic solvent, it has been found that a solution obtained by adding an electrolyte such as an acid, a salt, or an alkali to a diluted organic solvent is effective. Further, it has been found that a diluent of an acid is effective when bittern or the like is adsorbed.
That is, in the first invention, cleaning is performed using a diluent of an organic solvent. Further, in the second invention, cleaning is performed using a solution obtained by adding an electrolyte to a diluent of an organic solvent. Further, in the third, fourth, fifth, and sixth inventions, cleaning is performed using an electrolyte to which an acid, a salt, an acid, a salt, and an alkali are added, respectively, as the electrolyte. In the seventh aspect, the cleaning is performed using a dilute acid solution.
[0021]
[Action]
An outline of a sensor film in which various cleaning liquids used in the present invention are effective will be described.
1. The organic solvent is effective for almost all sensor films, and among the adsorbing substances, those having high hydrophobicity and adsorbing to the hydrophobic portion of the film are washed by utilizing the hydrophobicity of the organic solvent.
2. Acids are particularly effective for negatively charged lipid membranes such as phospholipids, and are used to remove any of the adsorbents that are positively charged and chemically react with negative lipid functional groups to form salts. This is carried out by utilizing the hydrogen ion substitution action. Thereafter, hydrogen ions are released (dissociation of functional groups of lipids) by co-washing with the reference solution or stabilization with the reference solution to restore the original state. At this time, after rinsing with an acid, excess hydrogen ions can be quickly released by simple rinsing with a neutral or weak alkali to speed up the measurement. Although the action of this acid can be considered with salts such as sodium chloride and potassium chloride, the replacement action of sodium ions and potassium ions is about 1/100 of that of hydrogen ions, so that the above action cannot be expected to be very effective.
[0022]
3. Salt is particularly effective for lipids having a positively charged group such as an ammonium group.Salt is a type of adsorbent that is negatively charged and chemically reacts with the positive functional group of the lipid to form a salt. This is performed by utilizing the action of substituting negative ions such as chlorine ions. Thereafter, chloride ions are released by co-washing with the reference solution or stabilization with the reference solution (dissociation of the functional group of the lipid) to return to the original state. At this time, after rinsing with salt, excess chlorine ions can be quickly released by a simple rinse of pure water to speed up the measurement. The action of this salt can also be considered with an acid such as hydrochloric acid, but since the substitution effect does not occur unless the concentration of the chloride ion, which is a negative ion, is made high, the acid also requires a high concentration and is substantially difficult to handle.
[0023]
4. Alkali is particularly effective for lipids having an ammonium group. In the ammonium group, a hydrogen ion is coordinated to the ammonium group, and a negatively charged adsorptive substance is chemically reacted with the hydrogen ion to form a salt. Then, when the alkali becomes alkaline, the coordination bond between the ammonium group and the hydrogen ion is released, and as a result, the adsorbed substance is released together with the hydrogen ion. Cleaning is performed using this action. Thereafter, the hydrogen ions are coordinated with the ammonium group by co-washing with the reference solution or stabilization with the reference solution to restore the original state. At this time, after rinsing with an alkali, hydrogen ions can be quickly coordinated by simple rinsing with an acid to speed up the measurement.
[0024]
5. In addition, even if the same type of film is used, an effective cleaning solution may be slightly different depending on the type of a substance adsorbed on the same type of film. For example, in the case of using only inorganic ions such as "shio" such as home salt and heavenly salt, washing of bitter components such as calcium and magnesium is effective only with acid.
These are summarized in Table 1 for each claim.
[0025]
[Table 1]

[0026]
In Table 1, the numbers indicate the types of molecular films listed in Table 2. Further, as can be seen from Table 1, there is a case where a plurality of types of cleaning liquids are effective even with the same molecular film. Those with () are (
) Is less effective than those without), but can be applied, for example, when it is desired to perform cleaning using the same cleaning liquid.
[0027]
[Table 2]

[0028]
【Example】
Hereinafter, examples of the present invention will be described.
In the first embodiment, a 30% aqueous solution of ethanol was used as a cleaning solution.
In the second embodiment, a 30% aqueous solution of ethanol and a 100 mM (m mole) aqueous solution of hydrochloric acid were used as the washing solution.
In the third example, a 30% aqueous solution of ethanol and a 2M (mole) aqueous solution of sodium chloride were used as the washing liquid.
In the fourth example, a 30% aqueous solution of ethanol, a 100 mM aqueous solution of hydrochloric acid, and a 2M aqueous solution of sodium chloride were used as the washing solution.
In the fifth embodiment, a 30% aqueous solution of ethanol and a 10 mM aqueous solution of sodium hydroxide were used as the washing solution.
In the sixth embodiment, a 100 mM hydrochloric acid aqueous solution was used as a washing solution.
Table 1 described above is also a table showing the results of an experiment for confirming the effect of performing the cleaning of the first to sixth embodiments.
[0029]
In Table 1, the embodiment corresponding to claim 1 in the left column is the first embodiment, the embodiment corresponding to claim 3 is the second embodiment, and the embodiment corresponding to claim 4 is the third embodiment. For example, an embodiment corresponding to claim 5 is the fourth embodiment, an embodiment corresponding to claim 6 is the fifth embodiment, and an embodiment corresponding to claim 7 is the sixth embodiment. The upper column shows the solution to be measured (the solution containing the adsorbed substance), and the other columns show that the substance adsorbed when the corresponding solution to be measured was measured was washed with the cleaning solution of the corresponding example, which was effective. Indicates the type of film.
The measurement was performed according to the first method of detecting horse mackerel (FIG. 1) described later. The effect was judged five times by the standard deviation of the measured value.
[0030]
From this result, it can be seen that the cleaning of the first embodiment is effective for most of the molecular films and most of the solutions to be measured. Therefore, it is considered that most of the adsorbed substances are adsorbed on hydrophobic portions of the membrane. If the cleaning of the first embodiment is not effective, the cleaning of the second embodiment is effective. The functional group of the molecular membrane (dioctyl phosphate) 1 is POOH, which is a minus membrane. This is the effect described above. In these two embodiments, cleaning for 90% of the whole can be performed. In particular, in the case of sake and beer, all molecular films can be washed.
In the examples, ethanol was used as the organic solvent. Methanol and acetone are also effective, but non-toxic ethanol is suitable for the taste sensor because it mainly targets food and drink.
[0031]
As described above, since the taste sensor can be washed, the method of detecting horse mackerel can be different from the general method described in the section of the prior art.
FIG. 1 shows an algorithm of a first horse mackerel detection method using the cleaning method of the present invention as a part thereof. Details will be described below.
1) Soak the taste sensor using the lipid membrane in the reference solution A for several hours. The reference solution A is composed of a salt, an acid, and a chemical substance having a cleaning action. In other words, it has both the function of calibrating the sensor and the cleaning function. When the reference liquid A is made of a salt and an acid having low adsorptivity to the lipid membrane, the effect of improving the sensitivity to the adsorbed substance is large.
2) Measure the sensor potential of the reference solution A.
3) In the case of batch-type measurement (a measurement method in which a solution to be measured is taken in, for example, a beaker), the sensor potential of the reference liquid A is measured again after putting the taste sensor in and out of the air a certain number of times. In the case of flow-type measurement (for example, a measurement method in which a solution to be measured and a reference liquid are respectively passed through a measurement pipe in which a taste sensor is set), the reference liquid A is allowed to flow through the taste sensor for a certain period of time, and then the reference is again measured. The sensor potential of the liquid A is measured.
4) Compare with the sensor potential of the reference liquid A measured one time before, and if the width of the change is within the set value, it is regarded as stable and proceed to 5) to measure the sensor potential of the sample. If the change width is equal to or larger than the set value, the process returns to 3). This has two meanings. One is to check the influence of the flow of the sensor and the flow of the measurement liquid as described in the related art, and periodically perform the operation of moving the sensor and the flow of the measurement liquid until the influence is eliminated. The other is to check whether or not the surface of the film has been refreshed by the cleaning liquid to a constant state. The finally stabilized sensor potential of the reference liquid is defined as VA.
5) When the sensor is stable, measure the sensor output (Vi) of the sample (solution to be measured) Si 2.
6) The measurement result 測定 Vi = Vi−VA of the sample Si is calculated.
7) When measuring samples continuously, proceed to 2).
[0032]
In the first agile detection method, the reference liquid A itself also serves as a cleaning liquid for the sensor, but the second agile detection method shown in FIG. 2 shows a measurement method in which a separate cleaning liquid is provided.
In this case, the reference solution A does not need to include a substance for washing as in the first horse mackerel detection method. After measuring the sample, a cleaning process of the substance adsorbed on the sensor is performed. As a specific cleaning process, for example, in the case of a batch type, the sensor is immersed in a cleaning liquid and moved, or the sensor is put in and out of the cleaning liquid.
[0033]
In the second method of detecting a horse mackerel, the reference solution A is synthesized with a substance having a low adsorptivity to a lipid membrane to improve the sensitivity to those substances. However, in the third horse mackerel detecting method shown in FIG. The following shows a measurement method in the case of using an object close to the measurement object containing an adsorptive substance or the measurement object itself. In this case, since the reference solution itself contains an adsorbable substance to the film, the cleaning process is performed even after the measurement of the reference solution.
[0034]
In the first to third methods, the reference liquid A is used not only for the original meaning of the calibration of the sensor potential, but also for the operation (stabilization) for removing the sensor and removing the influence of the flow. The fourth to sixth horse mackerel detection methods shown in FIGS. 4 to 6 use two types of reference solution A for stabilization and reference solution B for calibration of sensor potential, as described in the related art. The following shows the method of measurement.
[0035]
The fourth azimuth detection method (FIG. 4) is a measurement method in which the reference liquid A contains a substance for washing, as in the first azimuth detection method. The contents of the reference liquid A are the same as in the case of the first horse mackerel detection method. The contents of the reference liquid B are the same as the contents of the reference liquid A in the second horse mackerel detection method.
The fifth horse mackerel detection method (FIG. 5) is a measurement method in which a cleaning process is performed after measuring a sample. The contents of the reference liquids A and B are the same as those of the reference liquid A in the second horse mackerel detection method.
The sixth azimuth detection method (FIG. 6) is similar to the reference liquid A for the third azimuth detection method for the calibration reference liquid B of the sensor.
[0036]
In the detection method described above, the following processing may be performed.
(1) The stability check of the sensor with the reference liquid A may be performed once every several samples.
{Circle around (2)} In the stability check of the sensor with the reference liquid A, if the stability is poor, the process may return to the cleaning process (the second azimuth detecting method, the third azimuth detecting method, the fifth azimuth detecting method, the sixth azimuth detecting method). Horse mackerel detection method).
{Circle around (3)} Before the measurement of the sample, the reference solution A and the reference solution B, co-washing may be performed with each solution. In this case, in the first and fourth adjective detection methods, since the reference solution A contains a substance for washing, the co-washing itself is a washing process.
{Circle over (4)} Since the cleaning method differs depending on the type of the sensor and the type of the adsorbing substance, different cleaning processes may be performed. The cleaning process may be a combination of various cleaning processes.
[0037]
An example of an increase in the amount of information by a horse mackerel detection method using the washing method of the present invention for 14 brands of domestic beer and 12 types of domestic instant coffee using a taste sensor using a molecular film will be described. In the conventional method, the taste sensor is pre-soaked in beer for several days and stabilized, and the measurement procedure is almost the same as that of the first horse mackerel detection method (however, actual beer is used as the reference liquid). The method of detecting a horse mackerel using the cleaning method of the present invention is the first horse mackerel detection method. The results of principal component analysis of the measurement results are shown in FIGS. FIG. 7 shows the result of main component analysis of beer by the detection method to which the cleaning method of the present invention is applied, and FIG. 8 shows the result of main component analysis of beer by the conventional method. FIG. 9 shows the result of principal component analysis of coffee by the detection method to which the cleaning method of the present invention is applied, and FIG. 10 shows the result of principal component analysis of coffee by the conventional method. In the conventional method, the contribution rate of the first main component is 86.9% for beer and 92.0% for coffee, and the first main component has almost one-dimensional information in most cases. Is applied, the first principal component and the second principal component are orthogonal, and two-dimensional plus alpha information is obtained.
As an actual operation, a combination of a conventional detection method and a detection method to which the cleaning method of the present invention is applied may be considered. For example, in the case of coffee, No. 3 can be obtained by using the results of both the conventional detection method and the detection method to which the cleaning method of the present invention is applied using the film of No. 3. It is possible to obtain orthogonal two-dimensional information only with the three films.
[0038]
An example of the effect of washing with a dilute solution of ethanol will be described.
It shows that the reproducibility is good even when using a taste sensor using a molecular membrane to measure the wastewater, coffee and beer of rivers by synthesizing a reference solution with a simple salt and acid. The same washing solution and reference solution were used. In order to see the effect of removing adsorbed substances, a comparison was made between a reference solution A1 containing only salt and acid (30 mM potassium chloride and 3 mM hydrochloric acid) and a reference solution A2 obtained by adding 30% of ethanol to the reference solution A1. The measurement procedure is almost the same as the first horse mackerel detection method. However, the co-washing was performed with a liquid of the same component as the reference liquid before the measurement was transferred from the sample to the reference liquid. The results are shown in Tables 3 to 5. Table 3 shows the results of measurement of river sewage, Table 4 shows the results of coffee, and Table 5 shows the results of measurement of beer.
[0039]
[Table 3]

[0040]
[Table 4]

[0041]
[Table 5]

[0042]
The repetition measurement error (standard deviation) of the reference solution A2 to which ethanol was added was the same as that of the reference solution A1 to which no ethanol was added in Table 2 compared to the reference solution A1 to which ethanol was not added. 1, No. 5, no. Except for the film No. 6, the ratio was about 1/5 to 1/10, indicating the effect of washing ethanol. In addition, No. 1, No. 5, no. Also in the case of the film No. 6, the measurement error is significantly improved as in the case of the other films by performing the cleaning of the second to fourth embodiments.
[0043]
In the case of sake, a mixture of 3 mM succinic acid, 30 mM sodium chloride, and 40% ethanol was used as a washing solution, and a mixture of 3 mM succinic acid, 30 mM sodium chloride, and 15% ethanol was used as a reference solution. Since the measurement error is about 0.2 mV or less and the width of sake is 30 to 40 mV, the error rate is 1% or less, which is very high accuracy.
[0044]
【The invention's effect】
In the first invention, cleaning is performed using a diluent of an organic solvent. In the second invention, cleaning is performed using a diluent of an organic solvent to which an electrolyte is added. In the fourth, fifth, and sixth inventions, washing is performed by using an acid, a salt, an acid, a salt, and an alkali, respectively, as the electrolyte. In the seventh invention, an acid diluent is used. Because we decided to wash,
It has become possible to wash the taste sensor membrane, which has been difficult with the prior art.
Further, since the film can be washed, the following effects can be obtained.
That is,
{Circle around (1)} Since the sensitivity of the taste sensor to a substance adsorbed on the molecular film such as bitterness has been improved, the amount of information on taste has been increased.
{Circle around (2)} The synthesis of the reference solution was facilitated, and the reproducibility of the data was improved. (Even a simple standard solution of salt and acid can be measured with good reproducibility.)
{Circle around (3)} The range of the object to be measured has been widened.
[Brief description of the drawings]
FIG. 1 is a flowchart showing a first horse mackerel detection method using the cleaning method of the present invention.
FIG. 2 is a flowchart showing a second horse mackerel detection method using the cleaning method of the present invention.
FIG. 3 is a flowchart showing a third horse mackerel detection method using the cleaning method of the present invention.
FIG. 4 is a flowchart showing a fourth method of detecting a horse mackerel using the cleaning method of the present invention.
FIG. 5 is a flowchart showing a fifth method of detecting a horse mackerel using the cleaning method of the present invention.
FIG. 6 is a flowchart showing a sixth horse mackerel detection method using the cleaning method of the present invention.
FIG. 7 is a diagram showing the result of principal component analysis of the result of measuring beer by the first horse mackerel detection method using the washing method of the present invention, wherein (a) shows the first principal component and the second principal component; (B) is a diagram represented by a first principal component and a third principal component.
FIG. 8 is a diagram showing the result of principal component analysis of the result of measuring beer by the conventional horse mackerel detection method, which is represented by a first principal component and a second principal component.
FIG. 9 is a diagram showing a result of principal component analysis of a result of measuring coffee by a first horse mackerel detection method using the cleaning method of the present invention, wherein (a) shows a first principal component and a second principal component; (B) is a diagram represented by a first principal component and a third principal component.
FIG. 10 is a diagram showing a result of performing principal component analysis on a result of measuring coffee by a conventional horse mackerel detection method, which is represented by a first principal component and a second principal component.
FIG. 11 is a schematic diagram showing a lipid membrane in an expression method used in a method of designing a chemical substance.
12A and 12B are schematic diagrams of a taste sensor, wherein FIG. 12A is a front view and FIG. 12B is a cross-sectional view.
FIG. 13 is a diagram showing a measurement system for horse mackerel.
[Explanation of symbols]
1 Substrate (substrate)
2 electrodes
3 lipid membrane
4 buffer layer
5 Lead wire
11 Solution to be measured
12 containers
13 Taste sensor array
14 Each lipid membrane (indicated by black dots)
15 Reference electrode
16 buffer layer
17 Lead wire
18 Lead wire
19 Buffer amplifier
20 Analog switch
21 A / D converter
22 Microcomputer
23 XY recorder
31 Lipid molecules
31 'lipid molecules
32 membrane members
33 Matrix

Claims (7)

A cleaning method of a taste sensor film using the molecular film of the amphiphilic substances, preparing a diluted solution of an organic solvent as a cleaning liquid, and a step of washing the taste sensor film using the cleaning solution A method for cleaning a taste sensor membrane. The method for cleaning a taste sensor membrane according to claim 1, wherein the diluent of the organic solvent includes an electrolyte. The method for cleaning a membrane for a taste sensor according to claim 2, wherein the electrolyte is an acid. The method for cleaning a taste sensor membrane according to claim 2, wherein the electrolyte is a salt. The method for cleaning a membrane for a taste sensor according to claim 2, wherein the electrolyte is an acid and a salt. The method for cleaning a membrane for a taste sensor according to claim 2, wherein the electrolyte is an alkali. A cleaning method of the amphiphilic substances molecular film taste sensor film using the, preparing a dilute solution of an acid as the cleaning liquid, and a step of washing the taste sensor film using the cleaning solution A method for cleaning a membrane for a taste sensor.

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