Question

The heat treatment required to inactivate resistant bacteriophages is

• A. 72 °C/ 16 s
• B. 76 °C/ 30 s
• C. 80 °C/ 1 min
• D. 95 °C/ 1 min

Hint:

Resistant dairy bacteriophages survive HTST pasteurization and require $90\text{--}95^\circ\text{C}$ for $1\,\text{min}$ for total destruction.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Bacteriophages infecting lactic acid bacteria (such as Lactococcus lactis and Streptococcus thermophilus) disrupt cheese and fermented dairy fermentations.

Step 2: Detailed Explanation:
While standard milk pasteurization ($72^\circ\text{C}$ for $15\text{--}16\,\text{s}$) kills vegetative bacteria, certain thermally resistant bacteriophage strains can survive standard heat treatments.
Complete thermal inactivation of resistant dairy bacteriophages requires severe thermal processing at $90\text{--}95^\circ\text{C}$ for $1\text{--}5\,\text{minutes}$ (or $95^\circ\text{C}$ for $1\,\text{min}$).

Step 3: Final Answer:
Thus, inactivating resistant bacteriophages requires a heat treatment of 95 °C/ 1 min.