For many, the holiday season means tucking into a big meal with friends and family who gather to celebrate.
But once dinner is over, attention turns to packing the rest.
Each year, one in eight Canadians – about four million – are affected Food borne illness. Of those, there have been 11,600 hospitalizations and more than 230 deaths, the Public Health Agency of Canada estimates.
The possibility of leftovers can spark debate: How long does cooked food last? Is stale pasta really killing you? And should you throw away really hard things that have started to grow mold, or is it better to cut the pieces and eat the rest?
CBC News put those questions and more to Canadian food scientists – to save you the hassle and the fight. Here's what they said.
Can I leave cooked food on the counter for a week, as long as I reheat it every time I eat it?
Lawrence Goodridge, a food safety professor at the University of Guelph, said it's not a good idea to leave food out at room temperature.
“There's what's called the danger zone, which is between 4 degrees Celsius and 60 degrees Celsius,” Goodridge said in an interview. “Bacteria will grow very happily here.”
Advice for the kitchen”Keep hot food hot and cold food cold“Based on this temperature range.
For the cause, microbiologists point to a species of bacteria Bacillus cereus, June Can produce spores that can survive ripening.
Jennifer Ronholm, associate professor at McGill University, said that the bacteria a Heat-stable poison called cereulide which can cause serious illness.
“If you eat a small amount of ceruleid, you may experience vomiting, liver failure, respiratory problems, or even damage to muscle tissue that releases proteins and electrolytes into your blood and damage your heart and kidneys,” said Ronholm of Canada. Agricultural Microbiology Research Chair.
Death from Ceruleid Many are rare, Ronholm said. However, she pointed to a 2011 fatal case report of a 20-year-old man in Brussels, Belgium, linked to eating contaminated pasta. Bacillus cereus.
The pasta was prepared five days earlier and left in the kitchen at room temperature, the researchers said. Before his death, four fatal cases due to ceruleide had been reported, they said.
Should I cool a hot container of food before refrigerating it?
It's important to do everything you can to get the food container out of that danger zone as quickly as you can safely, Ronholm said.
Ronholm suggests placing the pot on the countertop and refrigerating it until steam begins to appear.
Balance is the goal, said microbiologist Keith Warner, a food science professor at the University of Guelph. If food containers are too hot when refrigerated, this can cause the temperature of the refrigerator to rise into the danger zone and produce condensation, which can allow microbial growth by pathogens such as listeria.
“However, modern refrigerators are very efficient at maintaining temperature and reducing condensation,” he said.
Does the depth of the container matter when I store cooked food?
Yes, it's important, said University of Saskatchewan assistant professor Kaidi Wang, who also holds the Agriculture and Agri-Food Innovation Chair in Applied Microbiology.
“Deep containers typically retain heat for longer periods of time, increasing the risk of bacterial growth,” Wang said.
Shallow containers Allow food to cool quickly, reducing time in the danger zone.
And smaller batches of food cool faster than larger ones, Warner said.
Time can be an important factor for something dangerous BacteriaWarner said. Clostridium perfringensOne of the fastest-growing bacteria, which can cause infections with symptoms like diarrhea and cramps. Bacteria can double in number every nine minutes.
“It doesn't take long to reach dangerous levels.”
Spores of Bacillus cereus According to the BC Center for Disease Control, it can germinate and grow in food stored between 8°C and 55°C for a sufficient period of time.
The bacteria “is a problem in room temperature storage of high starch foods (rice and pasta) and is responsible for death,” Warner said.
“Again, it comes down to how long the rice is kept in the danger temperature zone.”
How Long Do Residues Really Last?
You should always throw out food left out at room temperature for more than two hours, Ronholm said.
That's why it's best to portion things out, Goodridge said, such as keeping leftovers in the fridge or freezer.
e. A string of product recalls, including coli, listeria and salmonella, has raised concerns about food safety. Lawrence Goodridge, director of the Canadian Research Institute for Food Safety at the University of Guelph, says the data does not indicate an increase in recalls but adds that the pandemic has created some disruptions to food safety.
The general rule is that leftovers should be eaten within five days of cooking. Week-old food may look and smell fine, but some pathogens, e.g Listeria monocytogenes and Clostridium botulinumIt can grow under refrigeration temperatures and become a hazard, Warner said.
Beyond food safety, the University of British Columbia is offering tips Reducing food waste during the holidays.
I have some hard cheese that is just starting to mold. Can I cut it off and eat the rest?
Cheese texture matters, food scientists say.
Goodridge said that if the cheese is a hard cheese, at least 2.5 cm or an inch of cheese Mold should be removed around and below.
“Everything else, soft, semi-hard, should be discarded if mold is present,” Goodridge said. “Similar to other foods like bread.”
Ronholm said for hard cheese, mold is more of a quality issue than a safety issue.
“If we're talking about cottage cheese or ricotta or cream cheese, that's not true,” Ronholm said. With soft cheese, mold and toxins can penetrate more.
Do I have to warm my remains to a certain temperature?
Ronholm, who said she has four food thermometers, said yes.
Health Canada advises:: Reheat the leftovers to an internal temperature of 74°C and check with a digital food thermometer. Soups, stews and gravies should be reheated in a rolling boil.
