Intermittent sterilization - sterilization

This is a method of sterilization by repeated heating. It is used when the object to be sterilized may denature at the high temperature of high-pressure steam sterilization (120°C, 20 minutes). It is suitable for sterilization of biological preparations such as vaccines, and for sterilization of media that are easily denatured (coagulated, etc.) by heating such as carbohydrates, eggs, and serum. Usually, the object is sterilized by heating for 30-60 minutes once a day in water or circulating steam at 80-100°C under normal pressure, leaving it in air for 24 hours, and repeating this process for 3-5 days. In other words, the growing bacteria (vegetative cells) are killed in the first sterilization, but the dormant spores survive, so they are left in a state where they are easy to germinate (20°C or higher for 24 hours), and sterilized by waiting for the spores to germinate and become vegetative cells and then heating again. This is repeated three or more times to achieve complete sterilization. However, this is not suitable for anaerobic bacteria, as the spores do not develop into vegetative cells even if left for 24 hours, and remain as they are.

Low-temperature intermittent sterilization (pasteurization), which is often used to sterilize foods (such as milk), is a method of repeatedly heating at 60 to 80°C, and this "low temperature" refers to high temperatures, not low temperatures as they are commonly known. The intermittent sterilization process is also called tyndallization, and the low-temperature intermittent sterilization process is also called pasteurization.

[Fumiji Koho]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

加熱滅菌を繰り返して滅菌する方法。被滅菌物が高圧蒸気滅菌（120℃、20分間）の高温では変性をおこすおそれのある場合に行われる。ワクチンなどの生物学的製剤の滅菌や、炭水化物、卵、血清など加熱によって変性（凝固など）しやすい培地の滅菌などに適している。通例、平圧下80～100℃の水中または流通蒸気中で、1日に1回30～60分間加熱して24時間空気中に放置し、これを3～5日間繰り返すことにより滅菌する。すなわち、1回目の滅菌で、増殖中の菌（栄養細胞）は死滅するが休眠中の芽胞（胞子）は生き残るので、発芽しやすい状態（20℃以上で24時間）で放置し、芽胞が発芽して栄養細胞となるのを待って再度加熱することにより滅菌する。これを3回以上繰り返して完全に滅菌しようというわけである。ただし、嫌気性菌の場合は24時間放置しても芽胞は栄養細胞に発育せず、そのまま残存するので不適である。

　なお、食品（牛乳など）の滅菌によく使われる低温間欠滅菌（低温殺菌）は60～80℃で反復加熱する方法で、この「低温」は高温に対していうわけであり、いわゆる低温の意味ではない。また、間欠滅菌の操作をチンダリゼーションtyndallizationといい、低温間欠滅菌の操作はパスツーリゼーションpasteurizationともよぶ。

［幸保文治］

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