Whether you are at a campsite, in a stadium parking lot or out on the water, the cooler does the same job: keep cold food cold. The USDA and university extension services have clear, practical advice on how to pack one. Here are the tips that matter most.
Why the cooler matters
Bacteria grow rapidly between 40 and 140 °F, and above 90 °F outside, cold food heats to those temperatures much faster, according to the USDA. USDA FSIS adds that bacteria can reach dangerous levels after 2 hours (1 hour if it is 90 °F or above), and that your goal is to keep food out of that range. A cooler with a cold source is how you do it.
Start cold and pack full
- Start with cold food. Pack perishable food directly from the refrigerator or freezer. Meat and poultry may be packed while still frozen, and the USDA says it will stay colder longer. UMN Extension notes that adding frozen juices or meats helps keep other foods cold.
- Fill the cooler. A full cooler will maintain its cold temperatures longer than a partially filled one. If it is not full, the USDA says to pack the remaining space with more ice.
- Pack in reverse order. The first foods in should be the last foods used (USDA FSIS).
- Bring only what you need. USDA FSIS suggests taking foods in the smallest quantity needed, for example a small jar of mayonnaise.
Choose your cold source
USDA FSIS says a block of ice keeps food colder for longer than ice cubes, and suggests freezing water in clean, empty milk cartons or using frozen gel-packs. For a hike, it also suggests freezing some boxed drinks. UMN Extension recommends several inches of ice, or frozen gel packs, frozen juice or frozen water bottles. For boating, USDA FSIS suggests packing coolers with "several inches of ice, blocks of ice, or frozen gel-packs."
Keep it closed, shaded and separate
- Use two coolers if you can. USDA FSIS recommends one for drinks and snacks and another for perishable food, because the drink cooler is opened and closed a lot, which lets hot air in and melts ice faster.
- Limit opening. Open the lid only when necessary (UMN Extension), and open and close it quickly (USDA).
- Keep it out of the heat. Store the cooler in shade, or in an air-conditioned vehicle rather than the trunk (UMN Extension). At the campsite, USDA FSIS suggests insulating it with a blanket or tarp or keeping it in a shaded area. At the beach, the USDA suggests partially burying the cooler in the sand, covering it and shading it with an umbrella.
- Separate raw from ready-to-eat. Ideally pack raw meat or poultry in a separate cooler. With one cooler, put it below ready-to-eat foods (USDA FSIS).
- Use watertight containers. Food should not touch melting ice water (USDA).
- Add a thermometer. The USDA says to put an appliance thermometer in the cooler and make sure it reads 40 °F or below.
Tailgating, picnics and fishing days
For cold food at an outdoor event such as a picnic or sporting event, USDA FSIS calls a cooler with ice "a practical alternative to a refrigerator," packed with plenty of ice or frozen gel packs and kept in the shade when possible. Once food leaves the cooler, the 2-hour rule applies: 1 hour in air temperatures above 90 °F.
On the water, USDA FSIS notes that direct sunlight can be an even bigger problem, so keep the cooler closed, shaded or covered. This guidance covers food you bring along. It does not cover handling the fish you catch, so check your state wildlife agency for that.
The end of the trip
Leftovers are safe only if the cooler still has ice in it. When the trip is over, USDA FSIS says to discard perishable foods if there is no longer ice in the cooler or if the gel-pack is no longer frozen.
Where FluxCold fits
FluxCold ice sheets are 12 x 17 in, with 48 water-filled cells (4 x 12), about 1 lb each, flexible when frozen, and reusable. Freeze them overnight. Because they bend, you can lay one flat across the bottom of a cooler, slide one down the side, or place one on top of your food. You can also cut a sheet along the seams for a smaller cooler or lunch bag. When you are home, wash and refreeze it.
To be clear: the USDA examples above are ice, block ice, frozen gel packs, frozen drinks and frozen water bottles. They do not name FluxCold, and no agency has reviewed our product. Treat our sheets as one more reusable cold source in your cooler, and keep following the steps above: start cold, pack full, shade it and check a thermometer. See the FluxCold flexible ice sheets. Chill more, waste less!
Frequently asked questions
Is block ice better than cubes?
USDA FSIS says a block of ice keeps food colder for longer than ice cubes.
Should I use two coolers?
If you can. USDA FSIS suggests one for drinks and one for perishable food.
What temperature should the cooler be?
The USDA says an appliance thermometer in the cooler should read 40 °F or below.
How long can food sit out of the cooler?
No more than 2 hours, or 1 hour when it is above 90 °F (USDA FSIS).
Can I cut a FluxCold sheet to fit my cooler?
Yes. Cut along the seams between the cells.