Thermophilic Anaerobic Spoilage Causes

The spoilage type characterized by can swelling and a sour or cheesy odour is primarily caused by thermophilic anaerobic bacteria.

• Mechanism: These microorganisms are heat-loving (thermophilic) and thrive in the absence of oxygen (anaerobic). They ferment sugars within the canned food, producing significant amounts of gas (like hydrogen and carbon dioxide).
• Symptoms: This gas production causes the can to swell or bulge ('blown cans'). The metabolic processes of these bacteria also generate volatile acids and other compounds that result in a distinct sour or cheesy odour.

Distinguishing Spoilage Types

While other spoilage types may exhibit some similar characteristics, thermophilic anaerobic spoilage uniquely combines pronounced swelling with the specified sour/cheesy odour:

• Flat Sour: Causes a sour odour but typically does not result in can swelling as gas production is minimal or absent.
• Sulfur Stinker: Characterized by a sulfurous odour (rotten egg smell) due to hydrogen sulfide production, often without significant swelling.
• Flipper: Refers to cans that bulge due to gas but is a general term for swelling; the specific odour isn't the defining feature as it is for thermophilic anaerobic spoilage.

Therefore, the combination of swelling and a sour or cheesy odour points directly to spoilage by thermophilic anaerobic microorganisms.