Flat-sour spoilage agents in acid canned foods Flat-sour spoilage of acidic canned foods is classically attributed to which organism(s)? Choose the best answer for acid food matrices.

Introduction / Context:
Flat-sour spoilage describes acid production without gas, often detected by sour taste and decreased pH in intact cans. Correctly identifying the primary agent for acidic foods is important for selecting appropriate heat processes and raw material controls.

Given Data / Assumptions:

• Matrix: acid foods (for example, tomatoes and certain fruit-vegetable blends).
• Candidate organisms include Bacillus spp. with different thermal and pH preferences.

Concept / Approach:
Bacillus coagulans is the classic thermophilic, aciduric sporeformer responsible for flat-sour in acid and medium-acid foods. Bacillus stearothermophilus is more associated with flat-sour in lower-acid, near-neutral products (for example, some starch-rich foods). “Bacillus pepo” is not a recognized flat-sour agent in standard food micro texts.

Step-by-Step Solution:
Focus on acid matrix: favor organisms that tolerate pH below approximately 4.5–5.3.Select B. coagulans as the established acid flat-sour agent.Exclude misnamed or noncanonical organisms.

Verification / Alternative check:
Challenge studies with B. coagulans spores in acid foods demonstrate pH-tolerant growth with non-gassy souring outcomes.

Why Other Options Are Wrong:
“B. pepo” is not standard; B. stearothermophilus targets lower-acid, neutral pH matrices; C. botulinum produces gas and toxins under low-acid, anaerobic conditions and is unrelated to flat-sour in acidic cans.

Common Pitfalls:
Confusing flat-sour across pH ranges; assigning the wrong Bacillus species to acidic systems.

Final Answer:
Bacillus coagulans.