Packing a Lunch That Keeps: Insulated Bags and Ice Packs

A lunch that sits in a bag for four hours is a different food-safety problem from a lunch that goes straight from the fridge to the table. This guide sets out what Food Standards Agency (FSA) guidance, published on GOV.UK, says about keeping food cool away from home, and how insulated bags, ice packs and containers fit in. It also covers hot lunches, reheating at work and a few lunchbox ideas from the NHS. It is general information for healthy adults and school-age children, not medical advice. For choosing containers, see our meal-prep buying guide.

What "keeps" means

The FSA says a fridge should be between 0 and 5°C, and its picnic guidance treats 8°C and above as warm. After four hours or more at those temperatures, the risk from bacteria increases and food may become unsafe to eat. In extremely hot weather, the FSA says to use food that has been out of the fridge within 2 hours, and its heatwave advice says to try not to leave food out for longer than two hours when temperatures are higher than usual. A bag with an ice pack is meant to help keep chilled food cool until you eat; the FSA pages we read give no guarantee for any one bag, so keep to the time limits above. It is not a way to rescue food that has already warmed up.

Which foods need to stay cold

The FSA picnic page says to put foods that you would normally keep in the fridge into a cool box or cool bag with ice or frozen gel packs. It names cooked dishes, dairy products, and prepared salads and sandwiches. By that rule, anything you would normally keep in the fridge, such as a rice or pasta salad, cold meat or a dairy-based dressing, goes in the cold bag. Start with food that has already been chilled in the fridge: the pack's job is to hold the temperature, and pre-chilling is our reading of the FSA's advice to plan ahead so food stays cool until you are ready to eat.

Choosing the bag

• Size. It should hold your containers and an ice pack with the lid or zip fully closed. A bag you cannot close is not insulating.
• Lining. A wipe-clean lining is easier to keep hygienic; follow the maker's cleaning instructions.
• Separate bags. The FSA advises keeping perishable food in its own cool bag, closed until you plan to eat, and opening it as little as possible, with drinks in another.

A search for an insulated lunch bag on Amazon (opens in a new tab) shows the range of sizes.

Using ice packs

The FSA says to distribute ice packs throughout the box or bag, not all at the bottom, so that all the contents can be kept cold. It also says frozen drinks can help keep a cool box cold. Reusable gel packs are frozen in the freezer ahead of time, so keep a spare set freezing. Here is a search for reusable ice packs on Amazon (opens in a new tab). Check the maker's instructions for how long to freeze them and whether they can touch food directly.

Keep it out of the sun, and keep it closed

The FSA says to leave the cool bag in a shady spot out of direct sunlight, so not on a car dashboard or by a sunny window. If there is a fridge at work or school and you can use it, remember that the FSA says a fridge should be between 0 and 5°C. If you are unsure how long food has been out, the FSA advises a precautionary approach: do not eat it.

Hot lunches and flasks

An insulated food flask keeps hot food warm for a while, but it does not cool anything. The FSA's student guide gives the upper edge of the danger zone as 63°C, so, in our reading, a flask suits food that goes in steaming hot and is eaten soon after. The FSA pages we read give no time limit for flasks, so we do not give one; if a flask has sat for hours, the precautionary approach applies. A search for a vacuum insulated food flask on Amazon (opens in a new tab) shows the sizes.

Reheating at work

When you reheat a lunch in an office microwave, the FSA's rules are the same as at home:

• Reheat until it is steaming hot throughout, rather than warmed.
• Reheat only once, so take only the portion you will eat.
• Stir or turn the food, because microwaves can heat in pockets, and follow the microwave maker's guidance on standing.
• Rice needs extra care: the FSA says rice may be eaten cold if it was cooled quickly (ideally within one hour), should be kept in the fridge for no more than one day, and should be reheated only once until steaming hot all the way through.

Lunchbox ideas from the NHS

The NHS Healthier Families lunchbox page suggests basing the main item on foods like bread, rice, pasta and potatoes, choosing wholegrain where you can, and adding vegetables: cherry tomatoes or sticks of carrot, cucumber, celery and pepper all count towards 5 A Day. It also suggests bite-sized fruit, such as chopped apple, satsuma segments or berries, with a small pot of tinned fruit in juice rather than syrup as another option. Our guide to portion control without counting gives the NHS portion sizes for fruit and vegetables.

Containers for the bag

For a lunch that travels, look for a container with a closing lid that the maker describes as leakproof, and check that it also suits the microwave if you plan to reheat in it. Our buying guide explains the care marks to look for. A search for a leakproof lunch box with compartments on Amazon (opens in a new tab) is a starting point, and the maker's page tells you whether the base and lid can go in the microwave, freezer and dishwasher.

Take extra care with children and vulnerable groups

The FSA's heatwave and picnic advice names young children, pregnant women, older people and people with an underlying health condition as being at increased risk of food poisoning, and its heatwave advice says to take a precautionary approach if you are unsure how long food has been out. For a young child's lunchbox, that means keeping perishable items in the cold bag until eating and throwing away anything that has been out too long. Ask a GP, midwife or pharmacist if you are unsure which foods to avoid.

Where the links go

Links marked "on Amazon" open an Amazon search for the words in the link. Amazon decides what appears, so check each listing against the maker's instructions.

The date mark on the food and the maker's instructions on the bag and containers are the authority, ahead of any article, this one included. The FSA pages we cite apply to England, Wales and Northern Ireland; Food Standards Scotland publishes its own consumer food-safety advice. If you have a health condition or a weakened immune system, ask your GP or pharmacist.