JP2004180606A - Method and apparatus for drying guava leaf, guava leaf tea and method for producing the same tea - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To dry guava leaf in a short time without losing polyphenols. <P>SOLUTION: The washed guava leaf 40 is fed from a hopper 12 to a belt conveyer 23. Dried air kept at about 60°C, 20% humidity and 20 m/s air rate is fed from a nozzle pipe 29a to a first drying chamber chamber 24 and the guava leaf 40 is dried for 15 min in the chamber. Air kept at about 80°C and about 25% humidity is fed to a second drying chamber 25 and the guava leaf 40 is dried for 15 min in the chamber. Then, air kept at about 40°C and about 15% is fed to a third drying chamber and the guava leaf 40 is dried for 15 min in the chamber. Further, air kept at about 25°C and about 10% humidity is fed to a fourth drying chamber 27 and the guava leaf 40 is dried for 15 min in the chamber. The resultant guava leaf tea 41 comprises polyphenols in an amount of about three times, compared with ordinary tea and is suitable for health functional foods. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、グァバ葉の乾燥方法及び装置並びにグァバ葉茶及びその製造方法に関するものである。
【０００２】
【従来の技術】
近年の健康ブームと共に様々な健康食品が知られてきている。そのなかで、グァバの葉（以下、グァバ葉と称する）は、従来からお茶として飲用されている。近年の研究から、グァバ葉にはポリフェノール類が含まれており、ポリフェノール類は、糖質を分解する消化酵素の働きを抑制するため、血液中に入るブドウ糖の量が減少して血糖値の上昇を抑えることができることが分かってきた。お茶として利用されるグァバ葉茶は、採取したグァバ葉を直接蒸し器に入れて、蒸し工程で約１５０℃の温度で、５分蒸した後に、１２０℃〜１５０℃の温風を当てて１時間乾燥していた。
【０００３】
【発明が解決しようとする課題】
しかしながら、グァバ葉茶を製造する際、蒸し工程と高温乾燥工程とが必要であり、グァバ葉の緑色が失われ茶色に変色するために商品価値が低下する問題があった。さらに、グァバ葉中に含まれている有効成分であるポリフェノール類が減少する問題があった。
【０００４】
そこで、本発明は、ポリフェノール類の減少を抑制するグァバ葉の乾燥方法及び装置並びにグァバ葉茶及びその製造方法を提供することを目的とする。
【０００５】
【課題を解決するための手段】
本発明のグァバ葉の乾燥方法は、グァバ葉を第１温度で乾燥する第１工程と、前記第１温度よりも温度が高い第２温度で乾燥する第２工程と、前記第１温度よりも温度が低い第３温度で乾燥する第３工程とを含む。また、前記第３温度よりも温度が低い第４温度で乾燥する第４工程を追加することが好ましい。
【０００６】
前記第１工程は、前記第１温度が６０±５℃、湿度が２０±８％、乾燥時間が１５±１分、前記第２工程は、前記第２温度が８０±５℃、湿度が２５±８％、乾燥時間が１５±１分、前記第３工程は、前記第３温度が４０±５℃、湿度が１５±８％、乾燥時間が１５±１分である。前記第４工程は、前記第４温度が２５±５℃、湿度が１０±８％、乾燥時間が１５±１分であることが好ましい。また、本発明のグァバ葉茶は、没食子酸換算でポリフェノール類を９重量％以上１０重量％以下含有する。
【０００７】
本発明のグァバ葉の乾燥装置は、グァバ葉を載せて移動するメッシュベルトと、前記メッシュベルトの移動方向に沿って配置され、前記メッシュベルトが底となるように設けられ、メッシュベルト上のグァバ葉が順次通過する複数の乾燥室と、複数のノズル開口を備え、前記各乾燥室に対応するように、前記メッシュベルトの下方に配置されており、各乾燥室内の上流側から乾燥空気をメッシュベルトに向けて噴射し、乾燥室内の上流側でメッシュベルト上のグァバ葉を舞い上げて乾燥室内の下流側のメッシュベルト上に落下させるノズルパイプとを備えている。
【０００８】
【発明の実施の形態】
グァバ葉茶の製造に際して、まずグァバ（学名：Ｐｓｉｄｉｕｍ ｇｕａｊａｖａ Ｌｉｍｎ）の葉を収穫し、次に虫食いがされている葉や枯葉を除去する。この際に、収穫時に混入したゴミなども除去し、適正なグァバ葉のみを選別する。選別済みのグァバ葉を洗浄水を用いて洗浄する。洗浄水は、井戸水を５〜６日間養生し安定したものを使用することが好ましい。洗浄は、グァバ葉を洗浄容器に入れてバッチ式で行っても良いし、流水を用いた連続式で行っても良い。本発明では、大型の水槽にグァバ葉を入れてジェット水流方式で約１０分間洗浄することが、グァバ葉の洗浄を均一に行えると共に時間短縮のために好ましい。
【０００９】
グァバ葉の乾燥に用いられる乾燥設備１０を図１及び図２に示す。乾燥設備１０には、脱水機１１とホッパ１２と乾燥機１３と収納コンテナ１４とスクレーパ１５とが備えられている。乾燥機１３は、図示しない駆動装置により回転するローラ２０，２１と、その回転に伴って無端走行するメッシュベルト（以下、ベルトと称する）２２とを備えたコンベア２３を有している。なお、メッシュベルト２２には、スチールメッシュベルトを用いることが好ましいが、それに限定されるものではない。コンベア２３の通路に沿って第１乾燥室，第２乾燥室，第３乾燥室及び第４乾燥室２４，２５，２６，２７が設けられている。さらに、送風装置２８ａ，２８ｂ，２８ｃ，２８ｄが、各乾燥室２４〜２７とベルト２２を挟んで設けられている。各送風装置２８ａ〜２８ｄには、ノズルパイプ２９ａ，２９ｂ，２９ｃ，２９ｄが各乾燥室２４〜２７に対応して取り付けられている。なお、本発明に用いられる乾燥機は、図示した以外の公知のいずれも用いることができるが、温度と湿度を調整した熱風により乾燥を行う対流伝熱方式の装置を用いることが好ましい。
【００１０】
本発明の乾燥条件を具体的な数値を挙げて説明するが、本発明はそれら数値に限定されるものではない。前述した洗浄終了後、脱水処理を行い含水分量を１５±５％とすることが後に説明する乾燥工程の時間を短縮できるために好ましい。脱水処理は、脱水機１１で約５分行う。本発明において、重要なことは、乾燥工程以前のグァバ葉の蒸し工程を行わないことである。これにより、グァバ葉の緑色を失わないと共に含まれているポリフェノールの変質を抑制できる。また、従来のグァバ葉茶の製造方法では、洗浄，脱水処理を行っていない。
【００１１】
脱水機１１内のグァバ葉４０をホッパ１２から走行しているベルト２２上に排出し、ベルト２２の走行に伴って移動してグァバ葉４０を第１乾燥室２４に送る。第１乾燥室には、温度が６０±５℃、湿度が２０±８％の温風が風速約２０ｍ／ｓで送風装置２８ａから送風されている。第１乾燥室２４内を１５±１分で通過することによりグァバ葉４０を乾燥する。ここで、第１乾燥室２４内での乾燥方法の態様について、図３を参照して説明する。ベルト２２上のグァバ葉４０は、第１乾燥室２４内に入ると、ノズルパイプ２９ａから吹き付けられる温風３０ａ，３０ｂ，３０ｃ，３０ｄ，３０ｅにより室内の上方に舞い上がる（図３（ａ）参照）。温風３０ａ〜３０ｅは、ノズルパイプ２９ａのノズル開口（以下、開口と称する）３１ａ，３１ｂ，３１ｃ，３１ｄ，３１ｅ（図３（ｂ）参照）から吹き出す。なお、図３（ｂ）は、ノズルパイプ２９ａの設置位置を第１乾燥室２４の平面から示した図である。図３（ｂ）に示すように、開口３１ａ〜３１ｅの孔径は、上流側から下流側に向けて徐々に大きくし、またノズルパイプ２９ａを上流側に寄せて配置することが好ましい。これにより、図３（ａ）に示すように、グァバ葉４０は、第１乾燥室２４内の上流側で高く舞い上げられて、下流側でベルト２２上に落下してくる。そして、グァバ葉４０は、次の第２乾燥室２５内に送られる。このようにグァバ葉４０を第１乾燥室２４内で舞い上げて乾燥することで、乾燥効率を上げると共にグァバ葉４０のそれぞれの葉を均一に乾燥することができる。温風は、第１乾燥室２４と第２乾燥室２５との隙間から大気中に放出される。
【００１２】
第２乾燥室２５では、温度が８０±５℃、湿度が２５±８％の温風が風速約２０ｍ／ｓで送風されており、この第２乾燥室２５内で１５±１分乾燥される。次に第３乾燥室２６に送られ、温度が４０±５℃、湿度が１５±８％、風速約２０ｍ／ｓの温風で１５±１分乾燥される。最後に第４乾燥室２７内で温度が２５±５℃、湿度が１０±８％、風速約２０ｍ／ｓの冷風で１５±１分乾燥され、スクレーパ１５を用いて収納コンテナ１４でグァバ葉茶４１として回収する。第２乾燥室ないし第４乾燥室２５〜２７内でも前述した第１乾燥室２４内と同じ乾燥方法を行うので説明は省略する。
【００１３】
本発明のグァバ葉からグァバ葉茶を製造する方法によれば、蒸し工程を省略しているので有効成分の変成を抑制でき、さらにグァバ葉の自然色である緑色が維持され商品価値が上がるグァバ葉茶が得られる。有効成分のうち、特にポリフェノール類の含有量が従来法では２％〜３％であったが、本発明の乾燥方法を行うことで５〜６倍の含有量のグァバ葉茶４１を得ることが可能となる。また、乾燥条件も温度を２０℃〜８５℃とし、湿度を２％〜３３％の範囲とするので、特別な設備、例えば耐熱性材料等を用いていない乾燥設備により行うことが可能となる。また、グァバ葉茶４１中の含水分量は０％〜８％の範囲となり製品として好ましい範囲となる。さらに、グァバ葉を採取又は選別する際に、グァバの葉のみを用いて、茎を除くため効率良くグァバ葉茶を得ることができる。このグァバ葉茶４１を適当なサイズに裁断して製品とする。この裁断は、貯蔵前の方がグァバ葉茶の変色を防止するために好ましい。また、グァバ葉茶を製粉機、例えば石臼で挽くことにより、粉末のグァバ葉茶として販売することができる。このチップ状又は粉末状のグァバ葉茶は、緑茶と同様に茶立てをして飲用する。
【００１４】
【実施例】
以下、実施例を挙げて本発明を詳細に説明するが、本発明の態様はこれに限定されるものではない。また、後に説明する比較例で、実施例と同じ実験条件の箇所の記載は省略する。
【００１５】
［実施例］
茶畑から採取したグァバ葉１ｋｇから枯葉や虫食い物や茎を除去して、８００ｇを選別した。このグァバ葉をジェット水流式洗浄装置を用いて約１０分間洗浄を行った。なお、洗浄用の水は、井戸水を６日間養生して安定させ、水素イオン指数（ｐＨ）が６．８〜７．１のものを用いた。その後に、大型脱水機で５分間脱水して、水成分と固体成分（グァバ葉成分）とに分離した。
【００１６】
脱水したグァバ葉８００ｇを用いて乾燥を行った。図４に示す温度条件で乾燥した。始めに、第１乾燥室２４で温度を６０±５℃、湿度を２０±８％に制御した風速２０ｍ／ｓの風で１５分間乾燥し、次に、第２乾燥室２５で温度を８０±５℃、湿度を２５±８％に制御した風速２０ｍ／ｓの風で１５分間乾燥し、さらに、第３乾燥室２６で温度を４０±５℃、湿度を１５±８％に制御した風速２０ｍ／ｓの風で１５分間乾燥し、最後に第４乾燥室２７で温度を２５±５℃、湿度を１０±８％に制御した風速２０ｍ／ｓの風で１５分間乾燥し、グァバ葉茶４１を得た。
【００１７】
グァバ葉茶４１中に含まれるポリフェノール類の含有量を没食子酸換算で算出するために、没食子酸（ｇａｌｌｉｃ ａｃｉｄ）の検量線を作成した。
【００１８】
［没食子酸の検量線の作成］
没食子酸を精製水に溶解して、５種類の標準液を調製した。なお、精製水は、ｐＨが７．０のものを用いた。以下の説明でも、この特性を有する精製水を用いた。これら標準液を紫外可視分光光度計（Ｕ−３３１０形分光光度計）を用いて２００．００ｎｍ〜８５０．００ｎｍの波長範囲をサンプリング間隔０．５０ｎｍ、スキャンスピード３００ｎｍ／ｍｉｎで測定した。得られたスペクトルから６５０ｎｍ（式１）、７３５ｎｍ（式２）の吸収波長における検量線を最小二乗法で算出した。検量線は、波長６５０ｎｍを図５に示し、波長７３５ｎｍを図６に示す。
Ｙ＝０．０４６５Ｘ−０．０２５７，Ｒ^２ ＝０．９９９５・・（式１）
Ｙ＝０．０４３１Ｘ＋０．０２９９，Ｒ^２ ＝０．９９９６・・（式２）
ｘは、濃度（ｍｇ／１００ｍＬ），ｙは、吸光度（Ａｂｓ．）を示す。
【００１９】
［試料の調製］
グァバ葉茶を粉末状にして１．０ｇを秤量した。このグァバ葉茶と８０重量％メタノール水溶液６ｍＬとを５０ｍＬ遠心管に注入した。６０分間室温で浸透させた後に、遠心分離器を用いて４０００ｒｐｍで６０分間遠心した。その後に、上澄液を抽出液として用いた。
【００２０】
前記抽出液（試料溶液）０．２ｍＬと精製水３．２ｍＬとＦｏｌｉｎ−Ｄｅｎｉｓ試薬０．２ｍＬを混和した。その後にさらに、飽和炭酸ナトリウム水溶液０．２ｍＬを加え良く混和した。そして、３０分間反応させ、反応試薬入り試料液Ａ（以下、試料液Ａと称する）を得た。
【００２１】
前記Ｆｏｌｉｎ−Ｄｅｎｉｓ試薬に代えて、リン酸水溶液０．２ｍＬを加えて、それ以外は試料液Ａと同様の条件で反応試薬なし試料液Ｂ（以下、試料液Ｂと称する）を調製した。
【００２２】
さらに、試料液Ａ及び試料液Ｂを精製水を用いて１００倍にした反応試薬入り希釈液Ｃ（以下、希釈液Ｃと称する）及び反応試薬なし希釈液Ｄ（以下、希釈液Ｄ）を調製した。
【００２３】
［試料液の測定］
試料液Ａ，Ｂ及び希釈液Ｃ，Ｄの各測定は、前述した検量線作成用の紫外可視分光光度計を用いて常温下で、後述する箇所以外は同一条件で行った。なお、得られたスペクトル（以下、ＵＶスペクトルと称する）は、それぞれ図７ないし図１０に示す。
【００２４】
［ＵＶスペクトルの説明］
図７に試料液Ａを測定して得られたＵＶスペクトルを示す。ＵＶスペクトルよりポリフェノール類が含まれていることを示す最大吸収波長７３０ｎｍのブロードなピークＰ１が見られる。また、試料液Ｂを測定した図８のＵＶスペクトルＰ２では、８００ｎｍまで弱い吸収が見られたが、長波長側に反応（発色）を示す明瞭なピークは見られなかった。
【００２５】
また、希釈液Ｃ及び希釈液Ｄを前記測定方法と同じ方法でＵＶスペクトルを測定した。図９に示す希釈液ＣのＵＶスペクトルのピークＰ３は、最大吸収波長が６５０ｎｍであった。また、希釈液Ｄを測定した図１０のＵＶスペクトルには、６００ｎｍ〜８５０ｎｍの長波長側に明瞭なピークＰ４は、見られなかった。
【００２６】
以上に説明したように反応試薬が仕込まれた試料液Ａ及び希釈液Ｃでは、ＵＶスペクトルの５００ｎｍ〜８５０ｎｍの範囲にブロードなピークＰ１，Ｐ３が見られ、抽出液中にポリフェノール類の存在を確認できた。
【００２７】
［試料液中のポリフェノールの定量］
前述した没食子酸を用いた検量線（図５，図６参照）を用いて抽出液中のポリフェノール類の濃度の定量を行った。希釈液ＣのＵＶスペクトル（図９参照）から、吸収波長６５０ｎｍ及び７３５ｎｍにおける吸光度は、０．７３１，０．７２９であった。これら値の濃度を検量線（図５（式１），図６（式２））から算出すると、１６．３ｍｇ／１００ｍＬ、１６．２ｍｇ／１００ｍＬとなる。希釈液Ｃは、抽出液を１００倍しているので、抽出液中のポリフェノール類量は、これら各数値を１００倍した、１６．３ｍｇ／ｍＬ，１６．２ｍｇ／ｍＬとなる。これらの濃度は、抽出液を０．２ｍＬ用いた値であるので、グァバ葉茶中に含有しているポリフェノール類（没食子酸換算）の含有量は、濃度×６ｍＬ（抽出量）／０．２ｍＬ（測定量）から、９７．８ｍｇ，９７．２ｍｇとなる。グァバ葉茶に含まれるポリフェノール類は、没食子酸換算で重量百分率は９．８％，９．７％となる。従来のグァバ葉の乾燥工程を行った後に含有されているポリフェノール類は２％〜３％であるが、本発明のグァバ葉の乾燥方法を行うことで、ポリフェノール類の変成が抑制され、約９％〜１０％のポリフェノール類が含まれるグァバ葉茶が得られたことが分かった。
【００２８】
［反応時間の確認］
前述した反応試薬とポリフェノール類との反応時間を確認する実験を行った。前記精製水と没食子酸とから１０ｍｇ／ｍＬの濃度の没食子酸水溶液（以下、水溶液と称する）Ｅを調製した。この水溶液Ｅを前記反応試薬に混和して、前記紫外可視分光光度計で測定を行った。得られたＵＶスペクトルを図１１に示す。混和直後の吸光度は、０．３４であり、時間が経過すると共に没食子酸と反応試薬が反応し、吸光度が上昇した。図１１から明らかなように１８００ｓｅｃ（３０分）経った後に吸光度が０．５２と略一定となり反応が完全に進行したことが分かった。本実験により、前述したグァバ葉茶中のポリフェノール類の定量実験が正確であることが確認できた。
【００２９】
［再現性］
前記反応試薬とポリフェノール類（没食子酸）との反応時間を確認する実験を複数回繰り返して、各実験の吸光度の値から変動幅を求め再現性を確認した。なお、紫外可視分光光度計及び測定サンプルは、前記反応時間の確認の実験と同一の条件については、説明を省略する。始めに、同じ実験担当者が一日の間に、３回同じ実験を繰り返した。なお、実験担当者は、溶液分析及び機器分析の知識を十分に備えた者２名（Ｈ１，Ｈ２）により行った。実験担当者Ｈ１が、行ったときには、変動係数（Ｃ．Ｖ．）は、０．６５％であった。また、実験担当者Ｈ２が一日３回の実験（Ｈ１が実験を行った日とは別の日である。）を行ったところ、変動係数（Ｃ．Ｖ．）は０．６０％であり、再現性は良好であった。
【００３０】
また、日間の変動性を確認する実験も行った。実験は、連続した３日間に渡って行った。実験を行う際に、一度、前記紫外可視分光光度計のブランク実験を行い、その後に一回測定を行った。なお、実験開始時間は厳密には一定では無かったが、ほぼ同時刻から始めた。この実験を実験担当者Ｈ１，Ｈ２がそれぞれ３日間づつ行ったところ、変動係数（Ｃ．Ｖ．）は、それぞれ１．０６，１．５６％であり、良好な再現性が得られた。
【００３１】
以上、反応試薬にＦｏｌｉｎ−Ｄｅｎｉｓ試薬を用いて、測定検体をポリフェノール類とした場合、再現性が、日内変動，日間変動，実験担当者の変更のいずれにおいても極めて良好であるので、グァバ葉茶中に含有しているポリフェノール類の定量実験が適切に行われたことが分かった。
【００３２】
［比較例］
従来のグァバ葉の乾燥方法を行い、その適否の確認を行った。なお、実験結果を図１２にまとめて示す。実験は、温度が２０℃の乾燥風をとし、放置時間（乾燥時間）を１９時間〜２３時間の間とした実験（比較例１）を複数回行った。比較例１では含水分が１０％〜１５％であり、乾燥温度が低すぎることが分かった。
【００３３】
さらに、乾燥風の温度を３０℃，放置時間（乾燥時間）は、１５時間〜１８時間とした比較例２、４０℃，１１時間〜１４時間とした比較例３、６０℃，８時間〜１０時間とした比較例４、８０℃，６時間〜８時間とした比較例５、１００℃，４時間〜５時間とした比較例６、１２０℃，２時間〜３時間とした比較例７の各実験を行った。なお、特に明記しない実験条件は、比較例１と同じ条件で行った。
【００３４】
比較例２及び比較例３の各実験では、含水分が８％〜１２％の範囲であり、外観も緑色の色保持がなされた好ましいグァバ葉茶を得ることができた。しかしながら、これらの従来法では乾燥時間が１１時間〜１８時間かかるためコスト高になる。また、乾燥を乾燥容器で行うバッチ式で行うため、バッチ間での品質を一定に保つことに困難が生じる。また、比較例４及び比較例５の各実験でも、含水分が６％〜８％であり、色保持がなされたグァバ葉茶を得ることができた。しかしながら、これらの方法では、６０℃〜８０℃の熱風を送り続けるため、熱風の温度が下降しないように、乾燥容器の保温も行う場合も生じて光熱費が増加してコスト高の原因となる。さらには、比較例６及び比較例７の各実験では、グァバ葉茶がやや変色（比較例６）、茶色に変色（比較例７）してしまい、成分の変成が起きたと考えられる。また、グァバ葉茶の緑色が変色することで、商品価値も低下するため、１００℃以上での乾燥を数時間行うことは好ましくないことが分かった。
【００３５】
【発明の効果】
本発明のグァバ葉の乾燥方法によれば、グァバ葉を第１温度で乾燥する第１工程と、前記第１温度よりも温度が高い第２温度で乾燥する第２工程と、前記第１温度よりも温度が低い第３温度で乾燥する第３工程とを含むから、緑色が失われないグァバ葉茶が製造できる。また、グァバ葉中に含まれている有効成分、特にポリフェノール類が失われない。なお、前記第３温度よりも温度が低い第４温度で乾燥する第４工程をさらに含むとより前述した効果が生じる。
【００３６】
本発明のグァバ葉の乾燥方法によれば、前記第１工程の乾燥条件を、温度６０±５℃、湿度２０±８％、乾燥時間１５±１分とし、前記第２工程の乾燥条件を、温度８０±５℃、湿度２５±８％、乾燥時間１５±１分とし、前記第３工程の乾燥条件を、温度４０±５℃、湿度１５±８％、乾燥時間１５±１分とし、前記第４工程の乾燥条件を、温度２５±５℃、湿度１０±８％、乾燥時間１５±１分とするから、良好な緑色を有するグァバ葉茶の製造を行うことができる。また、グァバ葉中に含まれている有効成分、特にポリフェノール類が失われない。
【００３７】
本発明のグァバ葉の乾燥装置によれば、グァバ葉を載せて移動するメッシュベルトと、前記メッシュベルトの移動方向に沿って配置され、メッシュベルト上のグァバ葉が順次通過する複数の乾燥室と、前記各乾燥室に対応するように、前記メッシュベルトの下方に配置され、各乾燥室内の上流側から乾燥空気をメッシュベルトに向けて噴射し、乾燥室内の上流側でメッシュベルト上のグァバ葉を舞い上げて乾燥室内の下流側のメッシュベルト上に落下させるノズルパイプとを備えているから、緑色を保ったグァバ葉茶の製造を行うことができる。また、グァバ葉中に含まれている有効成分、特にポリフェノール類が失われない。
【図面の簡単な説明】
【図１】本発明の乾燥方法を実施するための乾燥設備の概略図である。
【図２】図１に示す乾燥設備の概略側面図である。
【図３】（ａ）は第１乾燥室の縦断面図であり、（ｂ）はノズルパイプの配置を示す説明的な平面図である。
【図４】本発明の乾燥方法の実験条件を説明するためのグラフである。
【図５】本発明の乾燥条件を説明するため、没食子酸水溶液の波長６５０ｎｍにおける検量線である。
【図６】本発明の乾燥条件を説明するため、没食子酸水溶液の波長７３５ｎｍにおける検量線である。
【図７】本発明の乾燥条件で得られたグァバ葉茶の抽出液に反応試薬を混合した試料溶液のＵＶスペクトルである。
【図８】本発明の乾燥条件で得られたグァバ葉茶の抽出液のＵＶスペクトルである。
【図９】図７で用いた試料溶液を１００倍に希釈した希釈液のＵＶスペクトルである。
【図１０】図８で用いた試料溶液を１００倍に希釈した希釈液のＵＶスペクトルである。
【図１１】図７で用いた反応試薬の反応時間を説明するためのグラフである。
【図１２】従来の乾燥方法の実験条件を説明するためのグラフである。
【符号の説明】
１０ 乾燥設備
２４，２５，２６，２７ 乾燥室
２８ａ，２８ｂ，２８ｃ，２８ｄ 送風装置
２９ａ，２９ｂ，２９ｃ，２９ｄ ノズルパイプ
３０ 温風
３１ａ，３１ｂ，３１ｃ，３１ｄ，３１ｅ 開口
４０ グァバ葉
４１ グァバ葉茶[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and apparatus for drying guava leaves, guava leaf tea and a method for producing the same.
[0002]
[Prior art]
Various health foods have been known along with the recent health boom. Among them, guava leaves (hereinafter referred to as guava leaves) have been conventionally consumed as tea. According to recent studies, guava leaves contain polyphenols, which suppress the action of digestive enzymes that degrade carbohydrates, which reduces the amount of glucose entering the blood and raises blood sugar levels. It has been found that can be suppressed. Guava leaf tea, which is used as tea, is obtained by putting the collected guava leaves directly into a steamer, steaming at a temperature of about 150 ° C for 5 minutes in a steaming process, and then applying hot air of 120 ° C to 150 ° C for 1 hour. It was dry.
[0003]
[Problems to be solved by the invention]
However, when guava leaf tea is produced, a steaming step and a high-temperature drying step are required, and there has been a problem that the green value of the guava leaves is lost and the guava leaves are turned brown so that the commercial value is reduced. Further, there is a problem that polyphenols, which are active ingredients contained in guava leaves, decrease.
[0004]
Therefore, an object of the present invention is to provide a method and an apparatus for drying guava leaves that suppress the reduction of polyphenols, guava leaf tea, and a method for producing the same.
[0005]
[Means for Solving the Problems]
The method for drying guava leaves of the present invention includes a first step of drying guava leaves at a first temperature, a second step of drying at a second temperature higher than the first temperature, and a method of drying the guava leaves at a temperature higher than the first temperature. Drying at a low third temperature. Further, it is preferable to add a fourth step of drying at a fourth temperature lower than the third temperature.
[0006]
In the first step, the first temperature is 60 ± 5 ° C., the humidity is 20 ± 8%, and the drying time is 15 ± 1 minutes. In the second step, the second temperature is 80 ± 5 ° C., and the humidity is 25%. In the third step, the third temperature is 40 ± 5 ° C., the humidity is 15 ± 8%, and the drying time is 15 ± 1 minute. In the fourth step, it is preferable that the fourth temperature is 25 ± 5 ° C., the humidity is 10 ± 8%, and the drying time is 15 ± 1 minute. The guava leaf tea of the present invention contains 9% by weight or more and 10% by weight or less of polyphenols in terms of gallic acid.
[0007]
The guava leaf drying device of the present invention is provided with a mesh belt on which a guava leaf is placed and moved, the mesh belt being arranged along a moving direction of the mesh belt, the mesh belt being provided at a bottom, and a guava on the mesh belt. A plurality of drying chambers through which the leaves sequentially pass, and a plurality of nozzle openings, are disposed below the mesh belt so as to correspond to the respective drying chambers, and mesh dry air from the upstream side of each drying chamber. A nozzle pipe is provided which injects the guava leaves on the mesh belt on the upstream side in the drying chamber and drops the guava leaves on the mesh belt on the downstream side in the drying chamber.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
In the production of guava leaf tea, first, guava (scientific name: Psidium guajava Limn) leaves are harvested, and then insect-eating leaves and dead leaves are removed. At this time, garbage mixed during harvesting is also removed, and only appropriate guava leaves are selected. The selected guava leaves are washed using washing water. It is preferable to use well water which is obtained by curing well water for 5 to 6 days and is stable. The washing may be carried out batchwise with guava leaves in a washing container, or may be carried out continuously using running water. In the present invention, it is preferable to put guava leaves in a large water tank and wash them for about 10 minutes by a jet water flow method so that guava leaves can be uniformly washed and time is shortened.
[0009]
FIGS. 1 and 2 show a drying apparatus 10 used for drying guava leaves. The drying equipment 10 includes a dehydrator 11, a hopper 12, a dryer 13, a storage container 14, and a scraper 15. The dryer 13 has a conveyor 23 including rollers 20 and 21 that are rotated by a driving device (not shown), and a mesh belt (hereinafter, referred to as a belt) 22 that runs endlessly with the rotation. In addition, although it is preferable to use a steel mesh belt for the mesh belt 22, it is not limited thereto. A first drying chamber, a second drying chamber, a third drying chamber, and a fourth drying chamber 24, 25, 26, 27 are provided along the path of the conveyor 23. Further, blowers 28a, 28b, 28c, 28d are provided with the drying chambers 24 to 27 and the belt 22 therebetween. Nozzle pipes 29a, 29b, 29c, 29d are attached to the blowers 28a to 28d, respectively, corresponding to the drying chambers 24 to 27, respectively. The dryer used in the present invention may be any known dryer other than the illustrated one. However, it is preferable to use a convection heat transfer type device that performs drying with hot air whose temperature and humidity are adjusted.
[0010]
The drying conditions of the present invention will be described with specific numerical values, but the present invention is not limited to these numerical values. After completion of the above-mentioned washing, it is preferable to perform a dehydration treatment to reduce the moisture content to 15 ± 5%, because the time of a drying step described later can be shortened. The dehydration process is performed by the dehydrator 11 for about 5 minutes. In the present invention, it is important that the step of steaming guava leaves before the drying step is not performed. As a result, the green color of the guava leaves is not lost, and deterioration of the polyphenols contained therein can be suppressed. Further, in the conventional method for producing guava leaf tea, washing and dehydration are not performed.
[0011]
The guava leaf 40 in the dehydrator 11 is discharged from the hopper 12 onto the traveling belt 22, and moves along with the traveling of the belt 22 to send the guava leaf 40 to the first drying chamber 24. Hot air having a temperature of 60 ± 5 ° C. and a humidity of 20 ± 8% is blown from the blower 28a into the first drying chamber at a wind speed of about 20 m / s. The guava leaves 40 are dried by passing through the first drying chamber 24 for 15 ± 1 minutes. Here, the mode of the drying method in the first drying chamber 24 will be described with reference to FIG. When the guava leaf 40 on the belt 22 enters the first drying chamber 24, the guava leaf 40 soars upward in the room by the warm air 30a, 30b, 30c, 30d, 30e blown from the nozzle pipe 29a (see FIG. 3A). . The warm air 30a to 30e is blown out from nozzle openings (hereinafter, referred to as openings) 31a, 31b, 31c, 31d, 31e of the nozzle pipe 29a (see FIG. 3B). FIG. 3B is a diagram showing the installation position of the nozzle pipe 29a from the plane of the first drying chamber 24. As shown in FIG. 3B, it is preferable that the diameters of the openings 31a to 31e are gradually increased from the upstream side to the downstream side, and the nozzle pipe 29a is arranged closer to the upstream side. Thereby, as shown in FIG. 3A, the guava leaves 40 are soared high on the upstream side in the first drying chamber 24 and fall on the belt 22 on the downstream side. Then, the guava leaves 40 are sent to the next second drying chamber 25. In this way, the guava leaves 40 are raised in the first drying chamber 24 and dried, so that the drying efficiency can be increased and the guava leaves 40 can be uniformly dried. The warm air is released into the atmosphere from a gap between the first drying chamber 24 and the second drying chamber 25.
[0012]
In the second drying chamber 25, hot air having a temperature of 80 ± 5 ° C. and a humidity of 25 ± 8% is blown at a wind speed of about 20 m / s, and is dried in the second drying chamber 25 for 15 ± 1 minute. . Next, it is sent to the third drying chamber 26 and dried for 15 ± 1 minute with warm air at a temperature of 40 ± 5 ° C., a humidity of 15 ± 8%, and a wind speed of about 20 m / s. Finally, it is dried in a fourth drying chamber 27 at a temperature of 25 ± 5 ° C., a humidity of 10 ± 8%, and a cool air having a wind speed of about 20 m / s for 15 ± 1 minutes, and the guava leaf tea is stored in a storage container 14 using a scraper 15. Collected as 41. The same drying method as that in the first drying chamber 24 described above is performed in the second to fourth drying chambers 25 to 27, and a description thereof will be omitted.
[0013]
According to the method for producing guava leaf tea from the guava leaf of the present invention, the steaming step is omitted, so that the metabolism of the active ingredient can be suppressed, and the guava leaf, which is the natural color of guava leaf, is maintained and its commercial value is increased. Leaf tea is obtained. Among the active ingredients, the content of polyphenols was 2% to 3% in the conventional method, but it is possible to obtain guava leaf tea 41 having a content of 5 to 6 times by performing the drying method of the present invention. It becomes possible. In addition, since the drying conditions are set to a temperature of 20 ° C. to 85 ° C. and a humidity of 2% to 33%, the drying can be performed by special equipment, for example, drying equipment not using a heat-resistant material or the like. The water content in the guava leaf tea 41 is in the range of 0% to 8%, which is a preferable range as a product. Furthermore, when collecting or sorting guava leaves, only guava leaves are used and stems are removed, so that guava leaf tea can be obtained efficiently. The guava leaf tea 41 is cut into an appropriate size to obtain a product. This cutting is preferred before storage to prevent discoloration of the guava leaf tea. Also, guava leaf tea can be sold as powdered guava leaf tea by grinding with a mill, for example, a stone mill. The guava leaf tea in the form of chips or powder is drunk in the same manner as green tea.
[0014]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples, but embodiments of the present invention are not limited thereto. Further, in comparative examples described later, description of portions under the same experimental conditions as in the examples is omitted.
[0015]
[Example]
Dead leaves, worms and stems were removed from 1 kg of guava leaves collected from a tea plantation, and 800 g were selected. The guava leaves were washed for about 10 minutes using a jet water washing apparatus. The water used for washing was prepared by curing well water for 6 days to stabilize the water, and the water used had a hydrogen ion index (pH) of 6.8 to 7.1. Thereafter, the mixture was dehydrated with a large dehydrator for 5 minutes to separate a water component and a solid component (guava leaf component).
[0016]
Drying was performed using 800 g of dehydrated guava leaves. It dried under the temperature conditions shown in FIG. First, drying is performed in a first drying chamber 24 for 15 minutes with a wind having a temperature of 60 ± 5 ° C. and a humidity of 20 ± 8% at a wind speed of 20 m / s. It is dried for 15 minutes by a wind having a wind speed of 20 m / s at 5 ° C. and a humidity of 25 ± 8%, and a wind speed of 20 m at a temperature of 40 ± 5 ° C. and a humidity of 15 ± 8% in a third drying chamber 26. / S wind for 15 minutes, and finally in a fourth drying chamber 27 for 15 minutes at a wind speed of 20 m / s controlled at a temperature of 25 ± 5 ° C. and a humidity of 10 ± 8%. Got.
[0017]
In order to calculate the content of polyphenols contained in the guava leaf tea 41 in terms of gallic acid, a calibration curve of gallic acid was prepared.
[0018]
[Preparation of calibration curve for gallic acid]
Gallic acid was dissolved in purified water to prepare five standard solutions. The purified water used had a pH of 7.0. In the following description, purified water having this property was used. These standard solutions were measured using an ultraviolet-visible spectrophotometer (U-3310 spectrophotometer) in a wavelength range of 200.00 nm to 850.00 nm at a sampling interval of 0.50 nm and a scan speed of 300 nm / min. From the obtained spectra, calibration curves at absorption wavelengths of 650 nm (formula 1) and 735 nm (formula 2) were calculated by the least square method. The calibration curve shows a wavelength of 650 nm in FIG. 5 and a wavelength of 735 nm in FIG.
Y = 0.0465X−0.0257, R ² = 0.9995 (formula 1)
Y = 0.0431X + 0.0299, R ² = 0.9996 (formula 2)
x indicates the concentration (mg / 100 mL), and y indicates the absorbance (Abs.).
[0019]
[Sample preparation]
Guava leaf tea was powdered and weighed 1.0 g. This guava leaf tea and 6 mL of an 80% by weight aqueous methanol solution were poured into a 50 mL centrifuge tube. After infiltration at room temperature for 60 minutes, the mixture was centrifuged at 4000 rpm for 60 minutes using a centrifuge. Thereafter, the supernatant was used as the extract.
[0020]
0.2 mL of the extract (sample solution), 3.2 mL of purified water, and 0.2 mL of Folin-Denis reagent were mixed. Thereafter, 0.2 mL of a saturated aqueous solution of sodium carbonate was further added and mixed well. Then, the reaction was performed for 30 minutes to obtain a sample solution A containing a reaction reagent (hereinafter, referred to as a sample solution A).
[0021]
Instead of the Folin-Denis reagent, 0.2 mL of a phosphoric acid aqueous solution was added, and a sample solution B without a reaction reagent (hereinafter, referred to as a sample solution B) was prepared under the same conditions as the sample solution A except for the above.
[0022]
Further, a diluent C containing a reaction reagent (hereinafter, referred to as a diluent C) and a diluent D without a reaction reagent (hereinafter, diluent D) prepared by increasing the sample liquid A and the sample liquid B by 100 times using purified water are prepared. did.
[0023]
[Measurement of sample liquid]
Each measurement of the sample liquids A and B and the diluents C and D was performed at room temperature using the above-described ultraviolet-visible spectrophotometer for preparing a calibration curve, under the same conditions except for the portions described later. The obtained spectra (hereinafter, referred to as UV spectra) are shown in FIGS. 7 to 10, respectively.
[0024]
[Description of UV spectrum]
FIG. 7 shows a UV spectrum obtained by measuring the sample solution A. From the UV spectrum, a broad peak P1 having a maximum absorption wavelength of 730 nm indicating that polyphenols are contained is observed. In the UV spectrum P2 of FIG. 8 in which the sample solution B was measured, weak absorption was observed up to 800 nm, but no clear peak indicating a reaction (color development) was observed on the long wavelength side.
[0025]
The UV spectra of the diluent C and the diluent D were measured by the same method as that described above. The peak P3 in the UV spectrum of the diluent C shown in FIG. 9 had a maximum absorption wavelength of 650 nm. Further, in the UV spectrum of FIG. 10 in which the diluent D was measured, no clear peak P4 was found on the long wavelength side of 600 nm to 850 nm.
[0026]
As described above, in the sample solution A and the diluent C into which the reaction reagents were charged, broad peaks P1 and P3 were observed in the range of 500 nm to 850 nm of the UV spectrum, and the presence of polyphenols in the extract was confirmed. did it.
[0027]
[Quantitative determination of polyphenol in sample solution]
The concentration of polyphenols in the extract was quantified using the above-mentioned calibration curve using gallic acid (see FIGS. 5 and 6). From the UV spectrum of the diluent C (see FIG. 9), the absorbances at absorption wavelengths of 650 nm and 735 nm were 0.731 and 0.729. When the concentrations of these values are calculated from the calibration curves (FIG. 5 (Equation 1) and FIG. 6 (Equation 2)), they are 16.3 mg / 100 mL and 16.2 mg / 100 mL. Since the diluent C is 100 times the amount of the extract, the amount of polyphenols in the extract is 16.3 mg / mL and 16.2 mg / mL, which are 100 times the respective values. Since these concentrations are values using 0.2 mL of the extract, the content of polyphenols (in terms of gallic acid) contained in guava leaf tea is: concentration × 6 mL (extracted amount) /0.2 mL From (measured amount), they are 97.8 mg and 97.2 mg. The weight percentage of polyphenols contained in guava leaf tea is 9.8% and 9.7% in terms of gallic acid. The polyphenols contained after performing the conventional guava leaf drying step is 2% to 3%. By performing the guava leaf drying method of the present invention, the denaturation of polyphenols is suppressed, and about 9%. It was found that guava leaf tea containing 10% to 10% of polyphenols was obtained.
[0028]
[Confirmation of reaction time]
An experiment was conducted to confirm the reaction time between the above-mentioned reaction reagent and polyphenols. A gallic acid aqueous solution (hereinafter, referred to as an aqueous solution) E having a concentration of 10 mg / mL was prepared from the purified water and gallic acid. This aqueous solution E was mixed with the above-mentioned reaction reagent, and the measurement was performed with the ultraviolet-visible spectrophotometer. FIG. 11 shows the obtained UV spectrum. The absorbance immediately after mixing was 0.34, and as time passed, gallic acid reacted with the reaction reagent, and the absorbance increased. As is clear from FIG. 11, after 1800 sec (30 minutes), the absorbance was substantially constant at 0.52, indicating that the reaction had completely progressed. This experiment confirmed that the above-described quantification experiment for polyphenols in guava leaf tea was accurate.
[0029]
[Reproducibility]
The experiment for confirming the reaction time between the reaction reagent and the polyphenols (gallic acid) was repeated a plurality of times, and the reproducibility was confirmed by obtaining a fluctuation range from the absorbance value of each experiment. The description of the UV-visible spectrophotometer and the measurement sample is omitted under the same conditions as those in the experiment for confirming the reaction time. Initially, the same experimenter repeated the same experiment three times during the day. The experiment was performed by two persons (H1, H2) who had sufficient knowledge of solution analysis and instrumental analysis. When experimenter H1 performed the experiment, the coefficient of variation (CV) was 0.65%. When the experimenter H2 performed an experiment three times a day (a different day from the day when the experiment was performed by H1), the coefficient of variation (CV) was 0.60%. And reproducibility was good.
[0030]
An experiment was also conducted to confirm daily variability. The experiments were performed over three consecutive days. At the time of conducting the experiment, a blank experiment of the ultraviolet-visible spectrophotometer was performed once, and then the measurement was performed once. In addition, although the experiment start time was not strictly constant, it was started almost at the same time. When this experiment was performed by the persons in charge of experiment H1 and H2 for three days, the coefficients of variation (CV) were 1.06 and 1.56%, respectively, and good reproducibility was obtained.
[0031]
As described above, when the measurement sample is polyphenols using the Folin-Denis reagent as the reaction reagent, the reproducibility is extremely good in any of daily fluctuations, daily fluctuations, and changes in the experimenter. It was found that the experiment for the quantification of polyphenols contained in the sample was properly performed.
[0032]
[Comparative example]
The conventional method of drying guava leaves was performed and its suitability was confirmed. The experimental results are shown in FIG. The experiment was conducted a plurality of times (Comparative Example 1) in which the drying air at a temperature of 20 ° C. was used and the standing time (drying time) was between 19 hours and 23 hours. In Comparative Example 1, the moisture content was 10% to 15%, and it was found that the drying temperature was too low.
[0033]
Furthermore, Comparative Example 2 in which the temperature of the drying air was 30 ° C. and the standing time (drying time) was 15 hours to 18 hours, Comparative Example 3 in which 40 ° C. and 11 hours to 14 hours, 60 ° C., 8 hours to 10 hours Each of Comparative Example 4 in which the time was 80 hours, Comparative Example 5 in which the temperature was 6 hours to 8 hours, Comparative Example 6 in which the temperature was 100 ° C. and 4 hours to 5 hours, and Comparative Example 7 in which the temperature was 120 ° C. and 2 hours to 3 hours An experiment was performed. Unless otherwise specified, experimental conditions were the same as in Comparative Example 1.
[0034]
In each of the experiments of Comparative Example 2 and Comparative Example 3, it was possible to obtain a preferable guava leaf tea having a moisture content in the range of 8% to 12% and having a green appearance. However, these conventional methods increase the cost because the drying time takes 11 to 18 hours. Further, since the drying is performed in a batch system in which the drying is performed in a drying container, it is difficult to keep the quality between batches constant. In each of the experiments of Comparative Example 4 and Comparative Example 5, guava leaf tea having a water content of 6% to 8% and retaining color was obtained. However, in these methods, since the hot air of 60 ° C. to 80 ° C. is continuously sent, the temperature of the hot air does not drop so that the drying container may be kept warm, which increases the utility cost and increases the cost. . Furthermore, in each of the experiments of Comparative Examples 6 and 7, it is considered that the guava leaf tea was slightly discolored (Comparative Example 6) and discolored to brown (Comparative Example 7), and the components were altered. Further, since the green color of the guava leaf tea changes color, the commercial value also decreases, so it was found that it is not preferable to perform drying at 100 ° C. or more for several hours.
[0035]
【The invention's effect】
According to the method for drying guava leaves of the present invention, a first step of drying guava leaves at a first temperature, a second step of drying at a second temperature higher than the first temperature, and the first temperature And drying at a third temperature lower than the third temperature, so that guava leaf tea without losing green color can be produced. Also, the active ingredients, especially polyphenols, contained in the guava leaves are not lost. Note that the above-described effect is obtained by further including a fourth step of drying at a fourth temperature lower than the third temperature.
[0036]
According to the method for drying guava leaves of the present invention, the drying conditions in the first step are a temperature of 60 ± 5 ° C., a humidity of 20 ± 8%, and a drying time of 15 ± 1 minute. The temperature was 80 ± 5 ° C., the humidity was 25 ± 8%, and the drying time was 15 ± 1 minute. The drying conditions in the third step were the temperature of 40 ± 5 ° C., the humidity of 15 ± 8%, and the drying time of 15 ± 1 minute. Since the drying conditions in the fourth step are a temperature of 25 ± 5 ° C., a humidity of 10 ± 8%, and a drying time of 15 ± 1 minute, guava leaf tea having good green color can be produced. Also, the active ingredients, especially polyphenols, contained in the guava leaves are not lost.
[0037]
According to the guava leaf drying apparatus of the present invention, a mesh belt that carries the guava leaf and moves, and a plurality of drying chambers that are arranged along the moving direction of the mesh belt and through which the guava leaf on the mesh belt sequentially passes. , Is disposed below the mesh belt so as to correspond to each of the drying chambers, injects dry air toward the mesh belt from the upstream side of each of the drying chambers, and guava leaves on the mesh belt at the upstream side of the drying chamber. And a nozzle pipe for dropping the guava leaf onto a downstream mesh belt in the drying chamber, so that it is possible to produce green guava leaf tea. Also, the active ingredients, especially polyphenols, contained in the guava leaves are not lost.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a drying facility for performing a drying method of the present invention.
FIG. 2 is a schematic side view of the drying equipment shown in FIG.
3A is a vertical sectional view of a first drying chamber, and FIG. 3B is an explanatory plan view showing an arrangement of nozzle pipes.
FIG. 4 is a graph for explaining experimental conditions of the drying method of the present invention.
FIG. 5 is a calibration curve of an aqueous gallic acid solution at a wavelength of 650 nm for explaining the drying conditions of the present invention.
FIG. 6 is a calibration curve of an aqueous gallic acid solution at a wavelength of 735 nm for explaining the drying conditions of the present invention.
FIG. 7 is a UV spectrum of a sample solution obtained by mixing a reaction reagent with an extract of guava leaf tea obtained under drying conditions of the present invention.
FIG. 8 is a UV spectrum of an extract of guava leaf tea obtained under the drying conditions of the present invention.
FIG. 9 is a UV spectrum of a diluent obtained by diluting the sample solution used in FIG. 7 by 100 times.
FIG. 10 is a UV spectrum of a dilution obtained by diluting the sample solution used in FIG. 8 by 100 times.
FIG. 11 is a graph for explaining the reaction time of the reaction reagent used in FIG. 7;
FIG. 12 is a graph for explaining experimental conditions of a conventional drying method.
[Explanation of symbols]
10 Drying facilities 24, 25, 26, 27 Drying chambers 28a, 28b, 28c, 28d Blowers 29a, 29b, 29c, 29d Nozzle pipe 30 Hot air 31a, 31b, 31c, 31d, 31e Opening 40 Guava leaf 41 Guava leaf tea

Claims (6)

グァバ葉を第１温度で乾燥する第１工程と、
前記第１温度よりも温度が高い第２温度で乾燥する第２工程と、
前記第１温度よりも温度が低い第３温度で乾燥する第３工程と、
を含むことを特徴とするグァバ葉の乾燥方法。A first step of drying the guava leaves at a first temperature;
A second step of drying at a second temperature higher than the first temperature;
A third step of drying at a third temperature lower than the first temperature;
A method for drying guava leaves, comprising: 前記第３温度よりも温度が低い第４温度で乾燥する第４工程を、さらに含むことを特徴とする請求項１記載のグァバ葉の乾燥方法。The method for drying guava leaves according to claim 1, further comprising a fourth step of drying at a fourth temperature lower than the third temperature. 前記第１工程の乾燥条件は、前記第１温度が６０±５℃、湿度が２０±８％、乾燥時間が１５±１分であり、
前記第２工程の乾燥条件は、前記第２温度が８０±５℃、湿度が２５±８％、乾燥時間が１５±１分であり、
前記第３工程の乾燥条件は、前記第３温度が４０±５℃、湿度が１５±８％、乾燥時間が１５±１分であり、
前記第４工程の乾燥条件は、前記第４温度が２５±５℃、湿度が１０±８％、乾燥時間が１５±１分であることを特徴とする請求項２記載のグァバ葉の乾燥方法。The drying conditions in the first step are as follows: the first temperature is 60 ± 5 ° C., the humidity is 20 ± 8%, and the drying time is 15 ± 1 minute.
The drying conditions in the second step are as follows: the second temperature is 80 ± 5 ° C., the humidity is 25 ± 8%, and the drying time is 15 ± 1 minute;
The drying conditions in the third step are as follows: the third temperature is 40 ± 5 ° C., the humidity is 15 ± 8%, and the drying time is 15 ± 1 minute.
The method for drying guava leaves according to claim 2, wherein the drying conditions in the fourth step are as follows: the fourth temperature is 25 ± 5 ° C., the humidity is 10 ± 8%, and the drying time is 15 ± 1 minute. . 没食子酸換算でポリフェノール類が９重量％〜１０重量％の範囲を含有することを特徴とするグァバ葉茶。Guava leaf tea, characterized in that the content of polyphenols is in the range of 9% by weight to 10% by weight in terms of gallic acid. 請求項１ないし３いずれか１つ記載のグァバ葉の乾燥方法を用いたことを特徴とするグァバ葉茶の製造方法。A method for producing guava leaf tea, comprising using the method for drying guava leaves according to any one of claims 1 to 3. グァバ葉を載せて移動するメッシュベルトと、
前記メッシュベルトの移動方向に沿って配置され、前記メッシュベルトが底となるように設けられ、メッシュベルト上のグァバ葉が順次通過する複数の乾燥室と、
複数のノズル開口を備え、前記各乾燥室に対応するように、前記メッシュベルトの下方に配置されており、各乾燥室内の上流側において、乾燥空気をメッシュベルトに向けて噴射し、乾燥室内の上流側でメッシュベルト上のグァバ葉を舞い上げて乾燥室内の下流側のメッシュベルト上に落下させるノズルパイプと、
を備えたことを特徴とするグァバ葉の乾燥装置。A mesh belt that moves with guava leaves on it,
A plurality of drying chambers arranged along the moving direction of the mesh belt, provided such that the mesh belt is at the bottom, and guava leaves on the mesh belt sequentially pass,
It has a plurality of nozzle openings, and is disposed below the mesh belt so as to correspond to each of the drying chambers. On the upstream side of each of the drying chambers, jets dry air toward the mesh belt, and A nozzle pipe that flies guava leaves on the mesh belt on the upstream side and drops on the downstream mesh belt in the drying chamber;
An apparatus for drying guava leaves, comprising:

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