Question

Sweet curdling of milk is due to

• A. E. coli
• B. S. aureus
• C. B. cereus
• D. L. lactis

Hint:

Sweet curdling = Enzymatic coagulation of casein by Bacillus cereus rennin-like proteases without acid production.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Milk spoilage is categorized by pH and curdling mechanism into acid curdling (lactic acid fermentation) and non-acid/sweet curdling.

Step 2: Detailed Explanation:
Sweet curdling occurs without significant acid production (milk pH remains near normal, $\text{pH} \approx 6.0\text{--}6.5$).
It is caused by spore-forming psychrotrophic or mesophilic bacilli, particularly Bacillus cereus (and Bacillus subtilis), which secrete rennet-like extracellular chymosin-like proteolytic enzymes that coagulate casein micelles into a soft curd without souring.

Step 3: Final Answer:
Therefore, sweet curdling of milk is caused by B. cereus.