Question

Fractional sterilization is also called

• A. Pasteurization
• B. Tyndallization
• C. Fractionation
• D. Dry heat sterilization

Hint:

Tyndallization = 3 Days of $100^{\circ}\text{C}$.
It relies on "tricking" spores into germinating so they can be killed by boiling temperatures.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
Sterilization is the total destruction of all microbes, including resistant endospores.
Fractional sterilization refers to a method of heating applied intermittently to achieve sterilization without using high pressure or extremely high temperatures.

Step 2: Detailed Explanation:

• Definition of Tyndallization: Tyndallization, named after John Tyndall, is a process of fractional sterilization by moist heat.
It is used for materials that are heat-labile and cannot withstand the high temperatures of an autoclave ($121^{\circ}\text{C}$).

• The Procedure: The material is heated to $100^{\circ}\text{C}$ (boiling/steaming) for about 20-30 minutes for three successive days.

• Mechanism of Sterilization:
- Day 1: Heating kills vegetative cells. Spores survive but are triggered to germinate into vegetative cells as the medium cools.
- Day 2: Heating kills the newly germinated vegetative cells.
- Day 3: A final heating ensures that any dormant spores that germinated late are destroyed.

• Distinction: Pasteurization (Option A) only reduces microbial load and doesn't kill spores. Dry heat (Option D) uses much higher temperatures (e.g., $160^{\circ}\text{C}$) in a hot air oven.

Step 3: Final Answer:
Fractional sterilization is scientifically referred to as Tyndallization.