Off-flavors in foods: A distinct musty or earthy flavor is most commonly attributed to which microorganisms in raw materials or water?

Introduction / Context:
Musty or earthy taints in foods, dairy, and drinking water are sensory defects that can lead to consumer complaints and product rejection. Pinpointing the biological source guides remediation.

Given Data / Assumptions:

• Off-flavor descriptors: ‘‘musty,’’ ‘‘earthy,’’ occasionally ‘‘moldy.’’
• Context: raw water used in processing, sediments, or soils contacting raw materials.
• Candidate microbes: actinomycetes, Flavobacterium, Pseudomonas.

Concept / Approach:
Actinomycetes (notably Streptomyces) produce geosmin and 2-methylisoborneol (MIB), potent odorants responsible for musty/earthy notes at extremely low thresholds. While other bacteria can cause off-odors, these specific descriptors strongly indicate actinomycetes.

Step-by-Step Solution:
Link sensory terms ‘‘musty/earthy’’ to geosmin/MIB. Identify primary producers in soils/sediments: actinomycetes. Select ‘‘Actinomycetes’’ as the best answer.

Verification / Alternative check:
Water utilities and food processors monitor actinomycete counts during algal blooms or after disturbance of sediments to control geosmin/MIB.

Why Other Options Are Wrong:

• Flavobacterium: can spoil foods but is not the classic source of earthy mustiness.
• Both (a) and (b): overinclusive; the signature compounds trace to actinomycetes.
• Pseudomonas syncyanea: not the canonical musty/earthy culprit.

Common Pitfalls:
Confusing sulfurous or rancid notes with earthy taints; the corrective actions differ.

Final Answer:
Actinomycetes