Question

‘Musty potato' aroma in milk is caused by __________.

• A. Achromobacter spp.
• B. Flavobacterium lactis
• C. Pseudomonas graveolens
• D. Pseudomonas mephetica

Hint:

Remember: "graveolens" means "strong-smelling" in Latin.
Pseudomonas graveolens is the classic culprit for "musty potato" flavor in milk.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Volatile off-flavors in pasteurized and raw milk are often traced to psychrotrophic bacterial growth during cold storage.
Certain bacteria synthesize heterocyclic, nitrogen-containing organic compounds that possess incredibly low sensory thresholds.

Step 2: Detailed Explanation:
The distinct "musty potato" (or potato-like) odor in cold-stored milk is a classic defect caused by {Pseudomonas graveolens (which has been reclassified under Pseudomonas taetrolens).
This cold-tolerant, aerobic, gram-negative bacterium is a common contaminant from soil and untreated dairy plant water.
During its log-phase growth in chilled milk, it metabolizes specific amino acids to produce volatile alkyl-methoxypyrazines, primarily 3-isobutyl-2-methoxypyrazine.
This chemical compound has an extremely low sensory threshold (detectable at parts-per-trillion levels) and produces a strong, unmistakable aroma of raw, musty, or rotting potatoes.
The other options, such as Pseudomonas mephetica, are associated with skunky or sulfury odors, while Flavobacterium causes sweetish or bitter proteolysis.

Step 3: Final Answer:
The "musty potato" aroma in milk is caused by Pseudomonas graveolens.