Question

Slimy or ropy cream is due to excessive growth of

• A. Pseudomonas fragi
• B. Escherichia coli
• C. Alcaligenes viscolactis
• D. Enterobacter faecalis

Hint:

Associate the root word "visco" in Alcaligenes viscolactis directly with "viscosity" or "slimy/ropy" defects in dairy products.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Ropiness is a bacterial defect in raw milk and cream characterized by an abnormal increase in viscosity.
The milk or cream becomes slimy, and when poured or pulled with a sterile loop, it forms long, thread-like structures.

Step 2: Detailed Explanation:
This viscosity defect is classified into two types:
- True Ropiness: Caused by the synthesis of extracellular gum-like polysaccharides or mucins by specific bacteria.
- False Ropiness: Caused by physical factors like acid precipitation of proteins or fat clustering.
True ropiness is primarily caused by {Alcaligenes viscolactis (also referred to as Alcaligenes tolerant).
This gram-negative, aerobic bacterium thrives under refrigeration temperatures (\(4\text{--}10^\circ\text{C}\)).
It metabolizes raw cream components to produce a thick, slimy capsule made of viscous, high-molecular-weight polysaccharides.
Since cream contains a higher fat content, the capsular material easily binds with the fat globule membranes, accelerating the formation of a highly cohesive, slimy mass on the surface of the cream.
Other organisms like Enterobacter aerogenes and certain strains of Klebsiella can also cause ropiness, but Alcaligenes viscolactis remains the classic cold-tolerant causative agent.

Step 3: Final Answer:
The excessive growth of Alcaligenes viscolactis is the primary cause of slimy or ropy cream.