Question

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A) : Clostridium tyrobutyricum is responsible for late blowing in cheese.
Reason (R) : Clostridium tyrobutyricum ferments lactose and produces \(\text{CO}_2\) leading to late blowing in cheese.
In light of the above statements, choose the most appropriate answer from the options given below.

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A).
• B. Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
• C. (A) is true but (R) is false.
• D. (A) is false but (R) is true.

Hint:

Remember: "Late blowing" occurs *late* in cheese ripening when all lactose has already been consumed by starter cultures. Thus, clostridia must ferment lactate (lactic acid), producing butyric acid, \(\text{CO}_2\), and \(\text{H}_2\).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
"Late blowing" is a major gas defect in semi-hard and hard cheeses (such as Emmental, Gouda, and Swiss).
It is caused by anaerobic, spore-forming bacteria that survive milk pasteurization and proliferate during the long ripening stages of cheese.

Step 2: Detailed Explanation:
Let us analyze both statements:
- Assertion (A) is correct: Clostridium tyrobutyricum is the primary organism responsible for late blowing.
Its highly heat-resistant spores survive pasteurization, germinate inside the cheese block during ripening, and cause structural splits, large irregular eyes, and a rancid butyric flavor.
- Reason (R) is incorrect: The metabolic pathway described is incorrect.
Clostridium tyrobutyricum does not ferment lactose to cause late blowing.
During the early stages of cheese making, active starter cultures (lactic acid bacteria) consume almost all lactose, converting it to lactic acid (lactate).
By the time the cheese reaches the ripening phase (when late blowing occurs), lactose is virtually absent.
Instead, C. tyrobutyricum ferments the accumulated lactate via butyric acid fermentation: \[ 2 \text{ Lactate}^- \rightarrow 1 \text{ Butyrate}^- + 2 \text{ CO}_2 + 2 \text{ H}_2 + \text{H}^+ \] The release of insoluble carbon dioxide (\(\text{CO}_2\)) and hydrogen (\(\text{H}_2\)) gases produces the gas pockets, while butyric acid causes the foul, rancid odor.

Step 3: Final Answer:
Assertion (A) is true, but Reason (R) is false because the substrate for fermentation is lactate, not lactose.