Beyond Salt and Smoke: Nine Modern Ways to Keep Food Safe

Salting preserves food with dry edible salt, which draws water out of bacteria and fungi by osmosis until they die or go inactive. It stayed the common way to keep meat until refrigeration displaced it in the mid-twentieth century, yet salt-preserved foods remain staples in North Africa, Scandinavia, coastal Russia and the Arctic.

Vacuum packing removes air before sealing, and without oxygen aerobic bacteria and fungi grow more slowly. It suits dry goods, cured meats, cheese, smoked fish and coffee, and for crushable items such as potato chips nitrogen gas can replace the air to protect the product.

Blast chilling cools cooked food from about 70 degrees Celsius to 3 degrees or below within 90 minutes, hurrying it through the roughly 8 to 68 degree range where bacteria multiply fastest. The page records that European Union regulations 852/2004 and 853/2004 require restaurants in member states to use it.

Flash freezing uses cryogenic temperatures or liquid nitrogen at about minus 196 degrees Celsius. The speed forms many small ice crystals instead of the few large ones that slow freezing makes, and the large crystals are what damage cell walls in slowly frozen food.

Freeze drying freezes a product and then lowers the pressure so the ice sublimates away without heat, which lets rehydrated food keep close to its original shape and flavor. The page notes the Inca made chuno from potatoes and the Japanese made koya-dofu from tofu long before industrial freeze drying began in the 1890s.

Thermization is a gentle heat treatment for milk, typically 57 to 68 degrees Celsius for 10 to 20 seconds, below the roughly 71 degrees for 15 seconds used in standard pasteurization. It keeps more of the milk taste and is used mainly to hold raw milk for cheese production, and European rules distinguish thermized cheeses from raw-milk cheeses.

Radappertization applies ionizing radiation at roughly 25 to 45 kilograys, enough that very few microorganisms remain detectable, viruses excepted. Shelf life then depends mainly on how well the packaging protects the food, and the name honors Nicolas Appert, the French pioneer of sterilized food preservation.

Pascalization, also called high pressure processing, applies more than 50,000 pounds per square inch for about fifteen minutes to inactivate yeast, mold, vegetative bacteria and some viruses and parasites. Because it has little effect on covalent bonds, it keeps sensory and nutritional quality better than heat does.

Hurdle technology combines several preservation steps, each called a hurdle, so that together they control pathogens and extend shelf life. Leistner defined it in 2000, and the page explains that a more intense hurdle improves safety but can harm quality, which is why mild hurdles are combined instead of one harsh treatment.