Packing a lunch for your child is a healthy and cost-effective option, however food poisoning bacteria can grow quickly, especially in the hot weather.

Food Safety Information Council spokesperson, Lydia Buchtmann, said recent research has shown that placing a frozen drink or ice pack in your child’s school lunch box keeps food safe for up to five hours.

A survey undertaken by the NSW Food Authority tested a range of sandwiches in lunchboxes. Some had ice bricks in them - for example a frozen popper drink - while some of them didn’t.

The survey also tested sandwiches in a brown paper bag without an ice brick.

The findings revealed the sandwiches in the brown paper bag were 12 degrees warmer then those in the lunch box with a frozen drink, and the lunch box without the frozen popper was only marginally cooler then the brown paper bag.

Ms Buchtmann said the findings were simple.

“The warmer food is and the longer it stays warm, the more bacteria grow,” she said. “If there are disease causing bacteria present they might grow too and that’s bad news as they can potentially make us sick.”

In addition to packing an ice bricks in your children’s lunch box, Ms Buchtmann said there were other precautions people could take.

“It’s fine to prepare lunch ahead of time provided the food is kept in the fridge and taken out just before the child leaves for school.”

She said parents could also choose low risk foods such as hard cheeses, freshly cooked meats and poultry, fresh, well washed fruits, canned tuna or salmon and shelf stable and sandwich spreads.

“When leaving home in the morning pack a frozen juice box, water bottle or commercial ice pack with the lunch and place the perishable foods such as cheeses and sandwiches between the frozen items.”

She said school bags also keep lunchboxes insulated, but only to a point.

“Lunchboxes kept inside the school bag will keep cooler longer if the bag is away from heat sources, such as direct sunlight,” she said.