How Long Boxed Broth and Cartons Really Last

The label says 12 to 18 months; Swanson prints 456 days on its carton against 730 on its can of the same broth. Stored cool, dry and standing up, a carton is fine for two or three years on quality, and food bank guidelines carry aseptic broth three years past the code date. Once it's open it is a fridge item: 4 to 5 days with the cap on.

Yes, if the carton is sound. It is aseptic, meaning sterile and sealed, and the date is the maker's quality estimate. A square, dry, firm carton with clean seams is still sealed; the broth may be a shade darker and a little flat. A bloated, sticky, leaking or soft carton has lost its seal and goes out unopened, whatever the date.

No. The food is equally sterile, but the container is not. A carton is paper, plastic and a foil layer thinner than a hair, heat-sealed at the edges; oxygen creeps in through the plastic seams and spout, corners crease, paper wicks water, and it punctures where a can dents. Broth is labeled 12 to 18 months in a carton and about 2 years in a can, and the can keeps going for 5 to 10 years where the carton is done in two or three.

Six layers of three materials: polyethylene outside, paperboard for stiffness (about three quarters of the weight), polyethylene, a sheet of aluminum foil thinner than a hair that does the real work of stopping oxygen and light, polyethylene, and polyethylene on the inside that the food touches. The broth is flash-heated to around 275 to 300°F for a few seconds, the carton material is sterilized in hot hydrogen peroxide, and the two meet in a sterile chamber. No metal ever touches the food.

Oxygen. Steel stops it completely; a carton's foil does too, but every seam, the spout and every creased corner is a place where only plastic stands between the broth and the air, and plastic only slows oxygen down. A little every day for a year flattens the taste and darkens the color. Add the carton's other weaknesses, crushed corners, wet board and pinholes, and the maker prints a shorter date.

Four to five days, capped, for broth, stock and soup; 7 to 10 days for UHT milk, plant milk and juice. The carton is a good fridge container because it reseals. Anything left after that goes into the stock pot or into the freezer in a jar.

UHT milk is labeled 6 to 12 months and is fine for about a year past that stored cool; food bank guidelines carry it one year past the code date. It browns slightly and tastes more cooked with age, which is sugar and protein reacting, not spoilage. Shake it; separation that shakes smooth is normal, lumps that do not are the end. Opened, 7 to 10 days in the fridge. Powdered milk is the storage answer: twenty years against one.

A light dent that pops back with the foil intact is fine. A bloated or pillowed carton, one that is firm when squeezed, means gas inside and something growing: out, unopened. A creased corner where the layers have parted, a soft or damp spot, a sticky patch or a lifted spout all mean the seal is suspect, and that carton is thrown out.

On the label, about the same or a little longer: boxed tomatoes run 18 months to 2 years against 18 to 36 months for the can. In practice they age differently. The can's limit is acid eating the tin and lining, so canned tomatoes go metallic and dark; the carton has no metal, so its limit is oxygen through the seals, and it tastes cleaner at a year old. Neither has the five-year legs of a can of beans. Rotate both inside two years.

Standing up, nothing stacked on top, off the floor, at 50 to 70°F in the dark. The failures are crushed corners and wet paperboard, so no cases of cans on top of a case of cartons and never under the water jugs. Date the cap end in marker the day it comes home. Same heat rule as cans: every 18°F of warmth halves the clock, and a garage summer puts a carton on its label date or worse.

A jar of broth concentrate like Better Than Bouillon is labeled about two years and keeps longer in a cool pantry; once opened it lives in the fridge for months. Bouillon cubes and powder are salt, fat and dried stock: labeled 1 to 2 years, they go stale rather than bad and keep for years if dry. A jar makes about 38 cups of broth from a quart of shelf space, which is why concentrate is the long-clock answer and cartons are kitchen food.

Both, in different places. Cartons for the kitchen rotation: they taste better, pour, reseal and weigh a third of a can. Cans for the deep shelf: the same broth carries 5 to 10 years in steel against two or three in a box, shrugs off a damp shelf and a stack, and tells you with a bulge when it has failed. A jar of concentrate and a tin of bouillon cover the gap between them.