Question

1. Describe the 5 methods of physically limiting microbial growth.
   1. Which methods are bactericidal?
   2. Which methods are bacteriostatic?

Answer 1

QUESTION-1

ANSWER

5 Methods of physically limiting bacterial growth.

1. Moist heat

2. Pasteurization

3. Refrigeration

4. Ionization radiation

5. Autoclaving

1. Moist heat

• Moist heat denatures bacterial protein leading to the death of bacteria.
• 2-3 hours is required to kill bacterial spores
• This is a physical bactericidal method.

2. Refrigeration

• At cold temperature, bacteria stops reproducing.
• It does not kill bacteria but it stops its growth.
• Used in food storage industries.

3.Ionization radiation

• It alters the chemical composition of bacteria.
• Highly reactive radicals, ions are produced in the cytoplasm which kills the bacteria.
• Gamma rays and X rays are used in ionization radiation.
• This method is used in food materials.

4.Pasteurization

• It lowers the bacterial content of milk and dairy products.
• It does not kill the bacteria but stops bacterial growth.

• Milk pasteurization is carried out for 30 minutes at about 62°C.

5. Autoclaving

• The materials are sterilized for 15 minutes at 121-degree Celsius in 15-pound pressure.
• This is used in microbial media preparation.
• This method kills the bacterial cells.

A. Bacteriocidal methods

• Ionization radiation
• Moist heat
• Autoclaving

These methods kill bacterial cells.

B. Bacteriostatic methods

• Pasteurization
• Refrigeration

These methods do not kill the bacterial cell but they reduce their growth. They do not allow them to reproduce.

GOOD LUCK.