A guide to holiday leftovers

Every Christmas, it seems there are two guarantees — a table stacked with enough food to feed an army and mountains of leftovers that inevitably end up in the fridge.

While leftovers always somehow seem that little bit tastier, it can become a gruelling task to get through the food in fear of wasting anything — but how long can leftovers really be stored for after Christmas Day?

Dr Kim-Yen Phan-Thien from the University of Sydney Faculty of Science has shared advice on food safety and managing leftovers in the holiday period.

Food safety and longevity are impacted by the way the food is treated. As a result, there isn’t one reliable rule to follow. Phan-Thien recommends the temperature control technique.

“When you serve food, hot food should be kept hot and cold foods should be kept cold. Food should be kept above 60°C or below five degrees, and in between five to 60°C is what we can think of as the danger zone,” she said. “This temperature range tends to promote microbial growth.”

While Christmas lunch can be an hours-long affair, it isn’t safe to leave food sitting on the table, vulnerable to the elements. Phan-Thien recommends putting out smaller portions and says some pathogens grow if food is left at ambient temperature for four hours.

Food that has been left out for several hours shouldn’t be kept as leftovers. Instead, food should be kept in the fridge and smaller portions should be brought out and replenished as necessary.

Food can sit on the table within a two-hour window and eaten as leftovers if it is stored in the fridge in that time frame. While it depends on the food, it is normally safe to eat within the next two to three days, but it is essential that the leftovers are reheated well.

“A turkey roast is generally safe to eat when cooked properly as the treatment will kill any pathogens there. However, if you’re going to store and eat the leftovers afterwards, you want to refrigerate or freeze them as quickly as possible,” Phan-Thien said.

If food has been in the danger zone for two hours, it must be eaten or refrigerated immediately. Leftovers should not be eaten if left out for more than four hours.

To keep leftovers fresh, Phan-Thien recommends packing smaller qualities into several containers. To avoid condensation inside the container, allow food to stop steaming before placing it inside.

On a hot Christmas Day, food may suffer from temperature abuse and a premature arrival to the danger zone.

“Be really conscious of temperature abuse and be prepared by having ice blocks available,” Phan-Thien said. “You can do things to increase the rate of cooling to help your food and your fridge out, like putting the food on ice for a bit to bring the temperature down before you stick it in the fridge.”

Instead of leaving cooked food out on a plate, it should be put on ice so it can last a bit longer in hotter temperatures.

If a fly lands on the food, it may transfer some pathogens, as flies are attracted to manure which may contain organisms such as Escherichia coli and Salmonella enterica.

“This does not necessarily mean food should be thrown away if a fly lands on it, but it varies case by case.

“They may land on manure, pick up some bacteria, then land on your food and transfer it there, but if it’s lightly touched your food and flown away, then the amount of risk that you’ve got an infectious dose is not great,” Phan-Thien said.

If food has been in the danger zone when a fly lands on it, pathogens can multiply and food safety risks increase.

“Also, remember, we need to be extra cautious when it comes to vulnerable people — the young, old, pregnant and immunocompromised — as these groups can become ill at a lower infectious dose,” Phan-Thien said.

When it comes to dogs eating leftover Christmas food, Dr Anne Quain from the University of Sydney’s School of Veterinary Science said she sees numerous dogs suffering from vomiting and diarrhoea after eating treats and leftovers from the table.

"Dogs often have a reasonably bland diet. A sudden influx of fatty festive foods can wreak havoc on their gut, leading to gastroenteritis, diarrhoea or pancreatitis. They can also suffer from intestinal obstruction or perforation due to foreign bodies like bones, kebab sticks and toothpicks,” Quain said.

If a pet is unwell, it is important to go to a vet without delay, particularly if their symptoms are vomiting or diarrhoea and they are refusing to drink. It may be a life-threatening condition, such as pancreatitis or gastric dilation (GVD).

Image caption: iStock.com/knape