Tyndallization is an alternative sterilization method. It is a physical method of sterilization that uses moist heat (steam) for sterilization. It is also known as fractional sterilization and intermittent sterilization. Physicist Dr. John Tyndall invented this technique of tyndallization in the nineteenth century. Therefore, to honor the work of Dr John Tyndall this sterilization procedure is named after him as Tyndallization. Sterilization by tyndallization is not effective as autoclave. This procedure involves intermittent exposure of substances to steam at 100 degree Celsius for 20–45 minutes for three successive days. This procedure is suitable for the sterilization of media containing thermolabile ingredients such as egg, serum and sugar.
This process mainly focuses on killing of spores. It takes about three days to sterilize any substance using tyndallization. The items to be sterilised are exposed to steam at 100 °C for 20 – 45 minutes for three successive days. The goal of this sterilization approach is to kill bacteria while they are in their vegetative state.
First exposure to steam at 100 °C will kill only vegetative bacteria. Incubation in moist condition allows dormant endospore to become vegetative bacterial cell forms. These vegetative bacterial forms are destroyed in next two days exposure to steam of 100 °C
Principle of Tyndallization:
Tyndallization is a multi-step technique which is effective for destroying bacteria spores. In this procedure products are placed in steam exposure at 100°C in a steam sterilizer for 20 – 45 minutes, followed by overnight incubation at 37°C, and this cycle is repeated next two days. Spores, if present, germinate into vegetative bacteria during the incubation period and get destroyed during steaming on the second and third days.
How tyndallization works:
Naturally, bacteria are present everywhere in two forms. The first is the vegetative form, and the second is the endospore form. Destroying bacteria in the vegetative form is easy because bacterial cell structures like cell wall ruptures quickly with heat. whereas the endospores are quite difficult to destroy. Endospores have a hard coating of calcium and dipicolinic acid. The endospore form is the dormant state of the bacteria. Bacteria go into this dormant state when they face an unfavorable environment. This dormant state is very resistant. When suitable and favorable conditions are provided for such spores, they become vegetative cells.
Tyndallization relies on the germination of spores to form vegetative cells. Heat exposure in the form steam at 100 °C kills all these vegetative bacterial cells at first exposure. Overnight incubation at 30 °C provides favorable environment in which endospores will germinate and destroying takesplace on the subsequent heating at 100 °C
Uses of tyndallization:
1. It main use is for destroying the endospore from the food products or nutrient media.
2. Mainly useful for steriliztion of media containing heat labile ingredients such as sugar, milk, gelatin.
3. It is suitable for sterilizing items which does not sustain high pressure and temperature of autoclaving.
Advantages of tyndallization sterilization:
1. It is more affordable, inexpensive method.
2. Tyndalls method of sterilization is simple.
3. Relatively low temperature (100 °C) during tyndallization procedure does not affect the product quality such as texture, flavor, appearance and nutrition.
Disadvantages of tyndallization sterilization:
1. This method is not suitable for all types of liquid substances.
2. It is time consuming process which takes three days to sterilize any items.
3. If large numbers of spores are present initially then they germinate as vegetative cells which becomes dead and remain in the medium.
4. It is not effective in destroying certain bacterial spores of anaerobic and thermophile bacteria.
It is not effective
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