Packing a Lunch That Keeps: Insulated Bags and Ice Packs

A packed lunch spends hours between your kitchen and your mouth, often in a bag with no refrigerator. This guide sets out what the USDA Food Safety and Inspection Service (FSIS) and the CDC say about keeping cold food cold and hot food hot on the way, so you can compare it with how you pack now. It is general information for healthy adults and school-age children, not medical advice. For choosing containers and tools, see our meal-prep buying guide.

Why the bag matters

FSIS says harmful bacteria multiply rapidly in the "Danger Zone", the temperatures between 40°F and 140°F, so perishable food carried without an ice source will not stay safe for long. It also says perishable food should not sit at room temperature for more than 2 hours, or 1 hour if the temperature is above 90°F. The CDC gives the same limits and gives a hot car as an example of the 90°F case. A lunch left in a hot car is therefore on a one-hour clock, not a two-hour one.

FSIS notes that prepackaged lunch combinations often contain perishable foods such as luncheon meats, cheese and cut fruit that must stay refrigerated, even though they may be cured or contain preservatives.

Start cold

• Cook and chill ahead. FSIS advises preparing cooked foods such as turkey, ham, chicken and vegetable or pasta salads ahead of time so they chill thoroughly in a refrigerator at 40°F or below, dividing large amounts into shallow containers for fast chilling.
• Prepare the night before, pack at the last minute. FSIS says it is fine to prepare food the night before, but to pack the lunch bag right before leaving home and to keep cooked food refrigerated until then.
• Freeze sandwiches. FSIS says freezing sandwiches helps them stay cold, although for quality you should not freeze ones containing mayonnaise, lettuce or tomatoes. Add those later.

Keep everything clean

FSIS says to wash your hands with soap and warm water for 20 seconds before you start packing, and to wash cutting boards, dishes, utensils and countertops with hot, soapy water after preparing each food item and before moving to the next. It also advises using a clean cutting board, and washing the board after cutting raw meat or poultry before you use it for foods that will not be cooked, such as bread, lettuce and tomatoes. FSIS suggests considering one board for fresh produce and a separate one for meat and poultry.

The commute and the first hour

FSIS points out that millions of Americans carry bag lunches by bus, bicycle, on foot, in a car or on the subway, and that perishable food must stay cold on the way and after arrival until lunchtime. It also says perishable food, including meat, poultry and eggs, should be kept cold at all times, and that eggs should be bought cold and kept cold at home. In practice, the lunch should go into a refrigerator, if one is available, as soon as you get there.

Two cold sources, top and bottom

FSIS recommends insulated, soft-sided lunch boxes or bags for keeping food cold, and says to pack at least two ice sources with perishable food in whatever bag or box you use. It gives two ways to do that: two frozen gel packs, each not smaller than 5 by 3 inches, or one frozen gel pack plus a frozen juice box or a frozen bottle of water. Freeze gel packs overnight and place them on the top and the bottom of the perishable items. If there is a refrigerator at work or school, FSIS says to store perishables there on arrival, and if you put the insulated bag itself in the refrigerator, to leave the lid or bag open so cold air can reach the food.

When you shop, the bag's insulation and the pack's size are the two things to read. Searches to start with are an insulated lunch bag on Amazon (opens in a new tab) and reusable ice packs for a lunch box on Amazon (opens in a new tab). A pack smaller than FSIS's 5-by-3-inch minimum is one to look at twice. Amazon decides what each search shows, so check the listing's dimensions and the maker's care instructions.

What needs no ice

FSIS lists foods that are safe without a cold source: whole fruits and vegetables, hard cheese, canned meat and fish, chips, breads, crackers, peanut butter, jelly, mustard and pickles. That is FSIS's list of examples, so treat any perishable food that is not on it as needing the cold sources described above.

Hot lunches

For soup, chili or stew, FSIS recommends an insulated container. Fill it with boiling water, let it stand for a few minutes, empty it and then add the piping hot food. Keep it closed until lunchtime so the food stays at 140°F or above. Our own caution: take care with the boiling water, especially if a child is helping. Searching for an insulated food jar on Amazon (opens in a new tab) shows many options, and the listing's stated hours of heat retention are the maker's own claim.

Reheating at work

FSIS says to cover food in the microwave to hold in moisture and promote even heating, and to reheat leftovers to at least 165°F, confirming it with a food thermometer. Frozen convenience meals should be cooked according to the package instructions. FSIS's microwave guidance also says to use only containers and wraps made for microwave use. It lists cold-storage containers such as margarine tubs and yogurt cartons, foam-insulated cups and trays, and metal pans among the things that are not safe in the microwave. Our hub guide covers how to read a container's care instructions.

Pack only what will be eaten

FSIS advises packing just the amount of perishable food that can be eaten at lunchtime, so there is no question about leftovers, and discarding leftover food, used packaging and paper bags after lunch. It says not to reuse packaging, because it could contaminate other food. A lunch that comes home half eaten is not a leftover to save.

Who should take extra care

FoodSafety.gov says children under 5, adults 65 and older, pregnant women and people with weakened immune systems are more likely to get sick from contaminated food, and asks them to chill cooked leftovers promptly, within 2 hours. If you pack for someone in those groups, treat the cold-source and time limits above as firm, and ask their doctor if you are unsure what applies.

Read next

• How to choose meal-prep containers: the buying checklist.
• Batch cooking and food safety: cooling, storing, freezing and reheating.
• Portion control without counting: plates, hands and containers.

The care instructions on your bag, packs and containers are the authority on how to use them. If you or the person you pack for has a health condition, ask a doctor about food precautions that fit.