Butter off-flavors — “fishiness” defect: Which organism is classically implicated in producing a fishy off-flavor in butter under poor hygiene or storage conditions?

Introduction / Context:
Butter is susceptible to a range of microbial and enzymatic off-flavors. Among these, a “fishy” odor is a recognizable defect linked to specific psychrotrophic contaminants that generate volatile amines and other odorous compounds, particularly when temperature and sanitation controls lapse.

Given Data / Assumptions:

• Error flavor: “fishiness.”
• Candidate organisms: Pseudomonas synxantha, Pseudomonas syncyanea, Aeromonas hydrophila, others.
• Butter: mildly salted, refrigerated product vulnerable to psychrotrophs.

Concept / Approach:
Pseudomonads in dairy environments often produce proteases and decarboxylases that yield amines such as trimethylamine and putrescine, associated with fishy odors. Among the listed species, Pseudomonas syncyanea has been historically associated with blue discolorations and fishy taints in dairy. Although P. synxantha produces yellow pigments and Aeromonas can cause spoilage in water and seafood, the classical pairing for the fishy butter defect is best matched with P. syncyanea.

Step-by-Step Solution:
Link fishy odor to amine production by psychrotrophs.Associate dairy fishy taint with P. syncyanea from classical defect tables.Exclude organisms primarily noted for other pigments/flavors.

Verification / Alternative check:
Historical dairy microbiology compendia note P. syncyanea among pseudomonads producing fishy taints in milkfat systems.

Why Other Options Are Wrong:

• P. synxantha: Usually linked to yellow pigments, not a prototypical fishy defect.
• Aeromonas hydrophila: Important in aquatic foods; less classically cited for butter fishiness.
• Bacillus licheniformis: More associated with rope or proteolysis in bread/dairy, not a signature fishy odor.
• None of these: A specific organism is classically implicated.

Common Pitfalls:
Overlooking psychrotrophic growth at refrigeration temperatures; even salted butter is not immune to pseudomonads introduced post-churn.

Final Answer:
Pseudomonas syncyanea.