Swelled cans in acid/medium-acid foods – The butyric acid type of fermentation with CO2 and H2 gas production is caused by which Clostridia?

Introduction / Context: In canned acid or medium-acid foods, a butyric fermentation can cause swelling due to CO2 and H2. Correctly identifying the organisms helps tailor process pH/heat hurdles.

Given Data / Assumptions:

• Product class: acid/medium-acid foods.
• Defect: butyric acid formation with gas (CO2, H2).
• Candidate organisms: various Clostridia.

Concept / Approach: Clostridium butyricum and Clostridium pasteurianum are classical butyric fermenters that can grow in lower pH ranges than proteolytic clostridia, generating gas and butyric odors, leading to swollen cans.

Step-by-Step Solution: Match fermentation type → butyric profile indicates C. butyricum/pasteurianum. Assess pH tolerance → these species tolerate lower pH, consistent with acid/medium-acid foods. Therefore, select “Both (a) and (b)”.

Verification / Alternative check: Isolations from gassy, butyric-smelling cans frequently yield these species; gas composition analysis confirms CO2/H2 dominance.

Why Other Options Are Wrong: C. sporogenes is proteolytic and better suited to low-acid foods; C. botulinum type E associates with seafood and lower salt, not the typical “butyric” defect outlined.

Common Pitfalls: Assuming any swell is botulinal; gas chemistry and odor profile are diagnostic clues.

Final Answer: Both (a) and (b).