Question

Ropiness in pasteurized milk/curd is caused by which of the following microorganism?

• A. Streptococcus fecalis
• B. Pseudomonas
• C. Alcaligenes
• D. Lactobacilli

Hint:

Association: "Alcaligenes viscolactis" $\rightarrow$ "Visco" (viscous) $\rightarrow$ Ropiness. This makes it easier to remember the function.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question refers to a specific type of spoilage in dairy products known as "ropiness," where the milk becomes viscous and forms threads or "ropes" when poured.

Step 2: Detailed Explanation:

• Ropiness is a texture defect in milk caused by the production of extracellular capsular polysaccharides (gums/mucus) by certain bacteria.

• Alcaligenes viscolactis is a primary causative agent of ropiness in milk. These bacteria are often found in water and soil and can contaminate milk through unhygienic handling or equipment.

• While some Lactobacilli (D) can cause ropiness in fermented products (like certain yogurts), Alcaligenes is the classic answer for this defect in fresh or pasteurized milk.

• Pseudomonas (B) is more commonly associated with bitter flavors or colorful spoilage (like blue or yellow milk).

• Streptococcus fecalis (A) is an indicator of fecal contamination but doesn't typically produce the characteristic "rope" texture.

Step 3: Final Answer: Alcaligenes is the microorganism primarily responsible for causing ropiness in milk.