Botulism

While fortunately rare in these days of better hygiene and public health, clostridium botulinum is an anaerobic bacterium – meaning it can grow even when oxygen is not present, for example in cans – which produces a deadly nerve toxin. It can, however, be killed by relatively brief exposure to a sterilizing or boiling temperature of 100°C/212°F, but its spores are more resilient and can only be killed at much higher temperatures over a prolonged period. Foods which have low acid levels, like meat, poultry, fish and fresh vegetables, are the most susceptible to bacterial contamination, while fruits such as tomatoes, which have high acid levels, are the least susceptible. For this reason, those intending to flavour oils with aromatics like herbs, chillies or garlic should first toss these flavouring elements in vinegar or lemon juice before immersing them in the oil.