Low-temperature cooking

History

Indigenous cultures, such as Samoans and Tongans, have long used low-temperature cooking in large pits for celebrations. The technique was first scientifically examined in the 18th century by Benjamin Thompson, who left meat in a drying oven overnight and found it tender and fully cooked the next morning. In 1969, Professor Nicholas Kurti of the University of Oxford repeated the experiments and determined that the temperature in Thompson's trial never exceeded 70 °C.

Theory

Meat is cooked to tenderise it, add flavours, kill harmful bacteria, and eliminate parasites like Trichinella spiralis and Diphyllobothrium. These goals can be achieved either by high heat for a short time or low heat for a long time, with lower temperatures requiring longer cooking. Toughness in meat comes from proteins such as actin, myosin, and collagen; heating them between 55 and 65 °C over an extended period causes denaturation, breaking them down and making the meat more tender.

Flavours can be enhanced by the Maillard reaction, which occurs above 115 °C and combines sugars and amino acids; meat may be browned at high heat before or after low-temperature cooking to gain benefits of both methods. Most harmful bacteria reside on the surface of unground meat, so for unprocessed steaks or chops it is usually safe to bring only the surface to a sufficient temperature for a few minutes. Ground meat requires cooking at a temperature and time adequate to kill bacteria throughout.

Poultry, due to its porous texture, can harbour pathogens internally even if the exterior is heated enough. Low-temperature cooking reduces the amount of fat and juices rendered from the meat, but when a plastic bag is used, little evaporation occurs, resulting in plentiful bag juices.

Did You Know?

• A dishwasher has been used to cook salmon.
• Sous-vide low-temperature cooking involves vacuum-sealing food in a plastic bag placed in a water bath or combi steamer with precisely controlled temperature.
• The food may be browned by heating the surfaces to about 200 °C using a roasting pan or blow torch prior to serving.