いわゆる「紅茶キノコ」の微生物と有機酸 Microbial Flora and Organic Acid Contents in “Tea Fungus”

「紅茶キノコ」と呼ばれる嗜好飲料の安全性の解明を目的として微生物学的ならびに有機酸組成の検討を行った.「紅茶キノコ」液から検出した微生物は <i>Acetobacter xylinum</i>, <i>Saccharomyces cereviciae</i>, <i>S. inconspicus</i>, <i>Candida tropicalis</i>, <i>Debaryomyces hansenii</i> などであった. これらの菌の凝塊形成至適温度は26～27°で, 菌の発育により紅茶液のpHは最終的に3.1以下となった. また, 本液に各種病原細菌を接種し生存性を検討した結果, いずれも48時間以内に死滅したことから, これらの菌により汚染される危険はほぼないものと考えた. 一方,「紅茶キノコ」液中に存在した有機酸の95%以上は酢酸で, 他に微量の乳酸およびギ酸が認められた.

To evaluate the safety of biological and chemical contents in “Tea fungus” as a kind of soft drink, microbial flora and organic acid content in this drink were investigated.<br>As the result of microbial investigation, <i>Acetobacter xylinum</i> was isolated from the drink as sole source of bacteria and other yeasts such as <i>Saccharomyces cerevisiae</i>, <i>S. inconspicus</i>, <i>Candida tropicalis</i>, <i>Debaryomyces hansenii</i>, were also found. Among those isolates tested, <i>A. xylinum</i> was found to be a zoogloeal mats forming organism, and the product was increased in cooperation with <i>S. cerevisiae</i>.<br>As the result of organic acid analysis by gas liquid chromatography, acetic acid, formic acid and lactic acid were found, especially acetic acid content occupied more than 95% of the total of them in this drink.<br>Several kinds of pathogenic bacteria such as <i>Salmonella typhi</i>, <i>Shigella sonnei</i>, pathogenic <i>Escherichia coli</i>, <i>Staphylococcus aureus</i>, were all died within 24 hours, when experimentally inoculated into the drink and incubation at both of 25°C and 37°C, though several kinds of filamentous fungi were found grow well in it.