Shipping food is a race against the clock, and the finish line is clear. USDA FSIS says perishable food should arrive frozen, partially frozen with ice crystals still visible, or at least refrigerator cold: below 40 °F as measured with a food thermometer. Here is how to pack a box so it has the best chance of getting there.
Know the numbers before you pack
Bacteria grow most rapidly between 40 °F and 140 °F, "doubling in number in as little as 20 minutes," and perishable food should not be left out for more than 2 hours, or 1 hour above 90 °F, according to USDA FSIS. You also can't judge a box by looking at it: USDA FSIS notes that pathogenic bacteria "may not affect the taste, smell, or appearance" of food. Even smoked, cured, vacuum-packed or fully cooked products are still perishable and must be kept cold, per the same FSIS page.
Step 1: Freeze the food first
Clemson Extension puts it simply: perishable foods "will stay at a safe temperature longest if frozen solid first." University of Tennessee Extension advises meat shippers to start with a frozen product and use overnight delivery, because a frozen start lets coolants such as gel packs or dry ice work more effectively.
Step 2: Choose a sturdy, insulated box
USDA FSIS says perishable items should be packed with a cold source in foam or heavy corrugated cardboard. University of Tennessee Extension adds that the outer box and insulation work together to keep products cold, keep heat out and protect against puncture, and that packaging should be as compact as possible.
Step 3: Add a cold source and close the gaps
For foods mailed from home, USDA FSIS suggests frozen gel packs or dry ice. If you use dry ice, don't touch it with bare hands, don't let it contact the food, and write "Contains Dry Ice" on the box. University of Tennessee Extension notes that dry ice is a hazardous material for air shipments and that some shippers will not carry it by air, so check with your carrier first.
Then deal with air. Clemson Extension says to fill empty space with crushed paper or foam, because "air space in the box will cause the food and cold source to thaw faster."
How much cold source do you need? That depends. NY Sea Grant lists the factors: the product and quantity, fresh or frozen, distance and timing, and the type of transport. Test a packed box on your own route before you ship to customers.
Step 4: Label it and ship early in the week
Mark perishable items and the outer box "Keep Refrigerated" and choose the fastest delivery, "ideally, overnight," says USDA FSIS. The same page advises sending packages early in the week so they do not sit in a mailing facility over the weekend, and not sending them to addresses without adequate refrigerator storage. Tell the recipient when to expect the box.
Step 5: Plan for a warm arrival
If perishable food arrives above 40 °F, USDA FSIS tells the recipient to notify the company and not to consume or even taste it. University of Tennessee Extension recommends that shippers decide in advance how they will handle product that arrives thawed. Put your refund or replacement policy in writing before the first order goes out.
Step 6: Reuse your cold sources
A cold source you can wash, refreeze and pack again means fewer things to throw away after every shipment.
Where FluxCold fits
FluxCold ice sheets are 12 x 17 in, with 48 water-filled cells (4 x 12), about 1 lb each, and they stay flexible when frozen. Freeze them overnight, then lay a sheet under and over your product so it drapes to the shape of the load. You can cut a sheet along the seams to fit a smaller box, and wash and refreeze it for the next order. Because they bend, they can help you fill gaps in a box. That is our own design observation, not a government claim.
To be clear about the guidance above: USDA's examples of cold sources are gel packs and dry ice. It does not name FluxCold, and nothing here means an agency has reviewed our product. Run your own test pack-out for your product and route.
Browse the FluxCold flexible ice sheets. For high-volume shipping, the 16 in x 9 ft Flexible Ice Blanket is cut to length and sold by quote. Chill more, waste less!
Frequently asked questions
Should food arrive frozen?
USDA FSIS says perishable mail-order food should arrive frozen, partially frozen with ice crystals still visible, or at least below 40 °F.
How many sheets do I need per box?
It depends on the box, the product, the distance and the weather, so there is no single number. Start with one under and one over the product, then test and adjust.
Can I cut a sheet to fit?
Yes. Cut along the seams between the cells.
Are the sheets reusable?
Yes. Wash, refreeze overnight and use again.
Is shipping food regulated?
Rules vary by product, state and carrier, and this guide is general information, not compliance advice. Check with your state or county health department and your carrier.