Canning food (thermal processing) is one of the oldest and most successful technologies still in use today to provide a safe product with a long shelf-life at room temperature. Very rarely do problems occur with sealing or leaking can seams. When they do, appropriate action is required, which may include a recall.
What is the risk to human health when things go wrong?
Most vegetables like beans, peas, carrots have a higher pH than 4.6; in other words, they tend towards the alkaline side of the pH scale. Canned vegetables together with canned fish and meat are therefore regarded as low-acid canned goods. This means that processing is focussed specifically on eliminating the microorganism Clostridium botulinum, which is associated with low-acid canned products if not heat-treated properly or if the integrity of the can is compromised. Commercial canning is very successful in achieving the goal of eliminating C. botulinum, where necessary because the heat treatment applied is well known, equipment used and post-processing handling are specific for this very purpose. Therefore, commercially canned foods are amongst the safest foods for human consumption. Most incidents of foodborne botulism occur from home-made canned or bottled foods. On very rare occasions, however, problems occur during commercial canning just as for any other manufacturing process.
Clostridium botulinum produces the toxin botulin (a neurotoxin) and when ingested causes the disease called botulism. When a can is damaged even after proper processing, this bacterium could potentially enter the can through pinholes and defective seams, from the external environment and produce the toxin, which can cause serious illness. Such contamination is extremely rare, however, and the risk is therefore very low. The other contents of the can will also help determine whether this organism will grow in the product or not, for example, if tomato sauce is present. Tomatoes are more acidic and could potentially lower the overall pH of such products to some extent. If the pH drops below pH 4.6, this would help to prevent the growth of C. botulinum.
Foodborne botulism
Foodborne botulism is extremely rare, but can be severe when contracted. Symptoms are:
- Difficulty swallowing or speaking.
- Dry mouth.
- Facial weakness on both sides of the face.
- Blurred or double vision.
- Drooping eyelids.
- Trouble breathing.
- Nausea, vomiting and abdominal cramps.
- Paralysis.
Signs and symptoms of foodborne botulism typically begin between 12 and 36 hours after the toxin has entered the body; but, depending on how much toxin was consumed, the start of symptoms may range from a few hours (as little as 6 hours) to a few days, sometimes as late as 10 days.
Receiving proper treatment as early as possible is vital. With correct treatment, one can fully recover from foodborne botulism. However, if not treated, the illness can be life-threatening. People receiving treatment recover in about 90% to 95% of cases, whereas it can be fatal to those not treated in 40% to 50% of cases.
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