How canned meat is made

Canned meat is cooked inside its own can, and the heat has to climb past 116 °C to kill botulism spores.

stations: 9
things upstream: 76
raw sources: 23
steps from the ground: 10

The short version

Grinders and mixers turn pork, ham or other meat into a seasoned paste with salt, water, starch and curing salt. Fillers load it into cans to a set weight, and a machine folds on the lid in a double seam. Washed cans go into retort baskets and cook under pressure above boiling, which kills botulism spores, then cool with care.

Grind the pork

Grinders, slicers and dicers reduce pork shoulder, ham or sometimes chicken or turkey. One famous canned meat was created to move a cut of pork that did not sell well.

Goes in
Pigs
Blend in the seasoning

Mixers work salt, water, sugar and a binder such as potato starch through the meat. Sodium nitrite goes in as a preservative. Particle size and fat level both affect how heat will later move through the can.

Goes in
Table salt Sugar Water
Fill to weight

Fillers portion the paste into metal cans. Overfilling changes the headspace and how heat penetrates, so checkweighers watch the line.

Goes in
Tin can
Pull a vacuum

Larger cans need a vacuum so pressure stays manageable in the cook. Canning plants use one of two methods: clinch the lid and heat the can in an exhaust box, or close it in a vacuum seamer.
Fold the double seam

A chuck grips the lid while it is crimped and interlocked with the can lip in two operations. The joint holds five layers of metal plus a sealing compound. An FAO canning guide asks for visual checks at least every 30 minutes.
Wash and load baskets

A conveyor carries sealed cans through a washer with detergent and water, then drops them into retort baskets.
Cook in a pressure retort

Baskets roll into a pressure vessel and heat well above boiling. Low-acid food like meat has to be sterilized this hot, because botulism spores survive plain boiling. Each product and can size needs its own schedule set by specialists.

116 to 130 °C
Cool without denting

Cans cool as gelatin forms from the meat and sets the filling into a block. The contents shrink, and the lids pull concave. Hot, wet cans are vulnerable, so rough conveyors and dirty cooling water can both ruin a seam.
Label and ship

Cans get inspected for dents and tilted ends, then labeled and boxed. They need no refrigeration.

Goes in
Cardboard box

End of the lineCanned meat

Worth repeating

Over 150 million pounds of Spam went to the US military during World War II.
Spam hit one billion cans in 1959, and sales have since passed nine billion.
A 109-year-old can of food from the wreck of the steamboat Bertrand showed no trace of microbial growth when tested in 1974.