Hands up if you've ever eaten cold rice with leftovers or a pasta or rice salad. Probably most, if not all, of us. Right?
Turns out eating cold rice or pasta can actually be quite dangerous -- and this is because of food poisoning-causing bacteria.
Every year in Australia there are around 4.1 million food poisoning cases. That means one in six of us experience food poisoning once a year. Not fun. And according to Chair of the Food Safety Information Council Rachelle Williams, cold rice and pasta make up a chunk of these food poisoning cases.
Why does eating cold rice and pasta cause food poisoning?
The reason why cold cooked rice and pasta can cause food poisoning is all to do with the potential bacteria content which grows after the grains have been cooked.
"In terms of food safety, uncooked pasta and rice are perfectly safe because they are dry, and bacteria don't like to grow in dry foods," Williams said.
"Once you cook them in water, the rice and pasta expand (because they're soaking up the water). This is an issue because bacteria like to grow in foods that are moist. The moment you add water to the rice and pasta, they suddenly become potentially hazardous foods. So, bacteria can grow in cooked rice and pasta if those foods aren't properly handled."
If we don't keep potentially hazardous foods cold (below 5°C) or hot (above 75°C) and we don't handle them properly, they're in the 'danger zone' -- we're allowing the bacteria to grow.
Potentially hazardous foods are things we intuitively know to keep in the fridge to prevent them from going off -- meat, poultry, cheese and other dairy products, eggs, cooked rice and pasta, and cut fruit and vegetables. You wouldn't eat chicken that's been left outside the fridge, and the same goes for cooked rice and pasta.
"If we don't keep potentially hazardous foods cold (below 5°C) or hot (above 75°C) and we don't handle them properly, they're in the 'danger zone' -- we're allowing the bacteria to grow," Williams said.
"If you keep those potentially hazardous foods below five degrees or above 60 degrees, we slow or stop the bacteria."
This goes for not only rice and pasta, but other grains which have been cooked in water.
"Cooked oats would become potentially hazardous, while dry oats are not a food safety issue. It's as soon as you add moisture to those foods."
How to safely store and consume cold rice and pasta
The above being said, it is possible to eat cold rice and pasta, provided you are storing and handling them properly. The below method goes for any potentially hazardous food, including leftovers and meat.
"If you're not using the cooked rice or pasta straightaway, the very first thing to do is to make sure you put the cooked drained pasta or rice into shallow containers -- if it's in one big, thick container it's going to take a long time to cool down to less than five degrees in the fridge," Williams said.
But don't put the hot cooked rice or pasta in the fridge straightaway.
"Putting something hot straight in the fridge will affect the temperature and food safety of the fridge, so what you need to do is put the food into shallow containers, leave it on the bench for 15-20 minutes (depending on the product) with the lid half on, and as soon as the steam vents and disappears, put on the lid and place it in the fridge.
"This way you're minimising the time the food is in the danger zone, and you'll be getting it into the fridge and cooled down as quickly as possible."
Then it's time for the second stage -- say you're making a pasta or rice salad.
"The second thing you need to do is make sure the rest of your ingredients have also been cooked, cooled down and handled properly," Williams said.
"When you're mixing all the ingredients, make sure you're using clean containers, clean utensils, forks, surfaces and hands by using detergent and then a sanitiser (a simple sanitiser is lemon or vinegar). Then do your mixing."
Then it's time to decide whether to store your rice or pasta salad, or serve it. But the timing here is key.
"If it's going to be served later for a buffet or lunch, once you've made the salad put on a lid and place it in the fridge. The longer the food is sitting in the danger zone, the more bacteria can grow," Williams said.
"When you do get it out, you've only got two hours before you need to decide what to do -- that two hours includes the preparation time. If it's taken half an hour to make, you've only got another hour and a half for that food to safely sit on the bench or buffet. If you do everything right you might still have some bacteria in there but minimal amounts."
Once the food has been served and the two hours is up, you have a few options.
"You can either throw it out, put it back in the fridge to get back out later (within 24 hours), or you can reheat it above the 65-75 degree mark," William said.
"But if you are going to reheat leftovers, you can only reheat it once. The reason is some bacteria will still survive the cooking in the fridge.
"You need to reheat to 75 degrees -- the temperature bacteria in food begins to be killed. The only way to tell if it's reached that temperature is to use a food thermometer to check."
While this seems like a lot of effort, it's worth taking precautions to avoid contracting (often dangerous) foodborne illness.
"I would say if you've handled cold cooked rice and pasta properly it's safe to eat. If it hasn't been handled properly or you're not certain, then don't eat the food. This is the same with all potentially hazardous foods."
What foods are most likely to cause food poisoning?
Surprisingly the number one food poisoning-causing food in Australia is eggs.
"Eggs are usually safe as long as the egg shells are intact (that is, the egg is whole). But as soon as the egg has been cracked, the bacteria in the air or on a surface can then get into the egg or us. Cracked eggs are the problem," Williams explained.
"Classic examples of this are mayonnaise and aioli, which is why we as the Food Safety Information Council recommend not making your own mayonnaise or aioli and to stick to supermarket versions.
"One of our biggest foods poisonings in Australia was caused by eggs that had been contaminated which ended up in raw egg mayonnaise used in many places.
"When you're cooking eggs you need to cook them to 72 degrees as this is when the bacteria present is pretty much controlled or killed. The best way to check is to use a food thermometer, so if you don't have one go and get one."
10 high-risk foods that can cause food poisoning
- Leafy greens and vegetables
- Raw milk
- Deli meats
Source: Food Safety Information Council.