Why are we more scared of raw egg than reheated rice?
Twenty-five years ago minister Edwina Currie sparked a scare over salmonella in eggs and had to resign amid outrage from farmers and plummeting sales. The panic has shaped the way we think about food safety.
There are foods that people instinctively associate with the risk of poisoning - raw chicken, raw egg, shellfish.
At the time of Edwina Currie's remarks - which were perceived to have dramatically exaggerated the prevalence of the disease in eggs in the UK - there were 12,302 cases of the salmonella PT4 strand most commonly found in poultry.
It dropped by 54% in the three years following the introduction of the British Lion scheme in 1998, which saw hens vaccinated against salmonella, and last year there were just 229 reported cases.
But people are still mistrustful.
How to avoid food poisoning
- Wash your hands, wash your worktops and wash your dishcloths and tea towels - and let them dry
- Take care with raw meat - chop it on a separate board, keep it away from ready-to-eat food and store on bottom of fridge (to avoid dripping)
- Ensure your fridge is below 5ºC; cool leftovers quickly after heating (within 90 minutes) and eat within two days
- Respect use-by dates
Pregnant women, the elderly and young children are warned against eating a runny yolk, and forums on parenting websites contain discussion threads on the perils of raw cake mix.
"The saying was that salmonella and eggs go together like a horse and carriage," says Sarah O'Brien, professor of Infection Epidemiology and Zoonoses at the University of Liverpool. "But that's not the case. Improved testing methods and improved treatment mean foods that used to be unusual causes of outbreaks have become the usual suspects."
It's impossible to precisely tally the number of cases caused by each type of food, but from what is known there are some less-expected culprits.
Watercress, beansprouts and curry leaves are believed to have been behind some of the most high profile outbreaks of food poisoning recently. People have died after eating contaminated celery, peanut butter and cantaloupe melon.
One of the more unusual outbreaks of food poisoning happened in 1951 in the French town of Pont-Saint-Esprit. Five people died and many suffered hallucinations after eating rye bread contaminated by ergot, a poisonous fungus. Ergot poisoning is, thankfully, easily avoided.
"Any food can be poisonous if it is not prepared or stored correctly," says Dr Haruna Musa Moda of the Food Research Centre at Manchester Metropolitan University.
"Chicken, eggs and shellfish are classed as high risk, but so are rice, pasta, couscous - starchy foods that have high moisture content. Ready meals and cooked meats are also on the high risk list, but people don't tend to think about them so much."
Many people are completely unaware of the dangers of eating reheated rice or pasta. Our perception of the risks is shaped by high-profile incidents.
Currie's remark that "most of the egg production in this country, sadly, is now affected with salmonella", caused a 60% drop in egg sales and she was forced to resign. The loss of revenue meant four million hens were slaughtered.
- Short for Escherichia coli - type of bacterium present in gut of humans and other animals
- E.coli infection happens when mutant strains are introduced to body, usually through food
- 119 people were infected during E.coli outbreak in Northern Ireland in 2012; several people died in Germany in 2011 after outbreak
But while the industry recovered, the egg's reputation for potential menace was longer lasting.
Salmonella in UK eggs is now very rare, but the official line that raw egg should be avoided will remain. "It is about knowing that the risk exists, even if it is small," says Bob Martin, of the Food Standards Agency.
Despite episodes like the Sainsbury's watercress recall it is hard for people to understand that non-animal products can be a risk. Beansprouts - including aduki, alfalfa, lentils and mung beans - have been associated with a number of health scares including an outbreak of salmonella in the UK in 2010.
"Salad leaves and green leafy vegetables can become contaminated with bugs, like salmonella and E.coli O157, from the soil," adds O'Brien. "Bagged salad, in particular, can have bugs that stick to the cut edge of the leaf - that is where the nutrients are and the bugs can be quite hard to get rid of by washing."
There are around one million cases of food poisoning each year, according to the Food Standards Agency. The majority are caused by the bug Campylobacter - commonly found in uncooked poultry, it is thought to be present in the vast majority of chickens.
But rice is also a common cause. It can contain Bacillus cereus, which is resistant to heat.
"It's one that a lot of people don't know about, but you do have to be very careful with rice," says Martin. "It's not that rice itself is dangerous but after it's been cooked there are spores of bacteria that can germinate."
The advice is to cool it quickly if it is likely to be eaten later. "Take the worst of the heat out but then put it in the fridge, it doesn't need to be room temperature any more - fridges have improved," adds Martin.
He also advises spreading it in shallow dishes to speed up cooling, or more simply, just cook the amount you want to eat. It's a very bad idea to eat rice that's been sitting in a buffet at room temperature after being cooked. Any reheating at home should be thorough but is only safe if the advice above has been followed.
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There is also official advice on the preparation on greens and salad. Wash vegetables under water rather than under a tap so germs are not sprayed around the kitchen. Vegetables should also be washed before they are peeled.
"Bear in mind that vegetables come from the soil which is a living thing. In some farms they are grown in soil with animal manure," adds Martin.
"The basic message is that all food should be treated with respect, don't abuse it, don't expect too much from it."