Butter flavor defects — ester (fruity) notes: Which organism is commonly associated with forming ester-like, fruity flavors in butter during spoilage?

Introduction / Context:
Butter off-flavors can be rancid, fishy, or fruity (ester-like). Fruity notes often signal microbial ester formation from alcohols and fatty acids. Identifying the organism helps guide cleaning, brine management, and cold storage practices.

Given Data / Assumptions:

• Defect: ester-like, fruity flavors in butter.
• Candidates include several Gram-negative spoilage bacteria from wet processing areas.
• We select the organism classically linked to fruity esters in dairy fats.

Concept / Approach:
Pseudomonas fragi is a well-known psychrotroph in dairy environments and is often implicated in fruity, ester-like off-flavors from lipolysis followed by esterification reactions. While other pseudomonads can cause pigmentation or proteolysis, P. fragi is classically tied to fruity defects in butter and cream.

Step-by-Step Solution:
Relate fruity/ester notes to microbial metabolism of fatty acids and alcohols.Identify P. fragi as the textbook culprit for fruity spoilage in butter.Exclude organisms linked to different defects (e.g., pigments, fishy taints).

Verification / Alternative check:
Butter defect charts routinely list P. fragi as a cause of fruity flavors, especially at refrigeration temperatures.

Why Other Options Are Wrong:

• P. synxantha: Yellow pigments more than fruity notes.
• P. mephitica / Aeromonas hydrophila: Not characteristically linked to fruity ester defects in butter.
• Lactococcus lactis: Starter bacterium; not a typical cause of fruity spoilage in butter.

Common Pitfalls:
Assuming fruity flavor is always desirable; in butter it indicates contamination and enzymatic activity from psychrotrophs.

Final Answer:
Pseudomonas fragi.