How to Pack a Lunch Safely

Why temperature matters

Bacteria grow fastest between 40°F and 140°F (4°C and 60°C), which USDA calls the Danger Zone. Perishable food should not sit in that range for more than two hours, or one hour if the air temperature is above 90°F (32°C). The aim of a well-packed lunch is to keep cold food at 40°F or below, and hot food at 140°F or above, until you eat it.

Keeping cold lunches cold

Choose an insulated bag

An insulated lunch bag or box holds the cold far better than a paper bag, which lets cold air escape and can tear as cold items thaw.

Use at least two cold sources

USDA recommends packing at least two cold sources, such as gel packs, a frozen water bottle or a frozen juice box, placed above and below perishable food. Frozen drinks do double duty: they keep the food cold in the morning and are thawed and ready to drink by lunchtime.

Pack it cold to begin with

Start with food straight from the fridge. If you pack lunches the night before, keep the whole bag in the fridge overnight, with the lid open so cold air can circulate, and add the cold packs in the morning.

Use a fridge if there is one

If you have access to a refrigerator at work or school, put your lunch in it as soon as you arrive.

Keeping hot lunches hot

Soups, stews and chilli can travel safely in an insulated vacuum container. Fill the container with boiling water, let it stand for a few minutes, then empty it and add the food while it is piping hot. Keep the lid closed until lunchtime so the food stays at 140°F or above.

Thick soups such as minestrone or lentil dal are ideal for this, as long as they are reheated until steaming hot before they go in.

Foods that travel well

Some foods are naturally lower-risk at room temperature and make good additions to any lunchbox, alongside properly chilled perishables:

• Whole fruit and sturdy vegetables such as carrots, apples and grapes.
• Crackers, bread, pretzels and other dry snacks.
• Unopened shelf-stable items, such as single-serve packs of peanut butter or canned tuna (pack them with cold sources once opened or mixed).
• Dips such as hummus, packed with a cold source.

After lunch

Throw away any perishable leftovers, used food packaging and paper bags rather than bringing them home to eat later. USDA advises against reusing packaging such as plastic bags or foil, which can carry bacteria onto other food.

Wash and sanitise the lunchbox or bag every day, including any reusable cold packs and containers, to remove crumbs and spills.

A quick packing checklist

1. Wash your hands and clean the counter before you start.
2. Pack perishable food straight from the fridge.
3. Add at least two cold sources to an insulated bag.
4. Preheat a vacuum flask for hot food.
5. Refrigerate the lunch on arrival if possible.
6. Discard perishable leftovers after lunch and clean the box each day.

Frequently asked questions

The bottom line

A safe packed lunch starts cold and stays cold: pack it from the fridge into an insulated bag with at least two cold sources, refrigerate it when you can, and keep hot food in a preheated flask. Clean the box daily and discard perishable leftovers, and your homemade lunches will be as safe as they are good.