How is smoking used for food processing and preservation?  

A number of food preservation techniques are used to increase shelf-life of products. Food preservation is the process of treating foods in a way that prevents spoilage caused by micro-organisms. However, there are also some food preserving techniques that not only preserve foods but enhance the flavour as well and one of these techniques is “smoking”.

Smoking is the process of flavouring, cooking, or preserving food by exposing it to the smoke from burning or smouldering plant materials like wood and that too hardwood. Smoking of food is done at the commercial as well as the home level. The meats are hung or placed on racks in an enclosed area so that the smoke does not escape and instead penetrates foods. Commercial smoking is sometime carried out with steam pipes that supplement the wood fire.

Since smoke is antimicrobial and antioxidant it is used to preserve foods. Smoking is probably the oldest food preservation method and could have developed shortly after fire was discovered. Due to the use of chemical preservatives the use of smoking as a preservative had declined but once again it is gaining popularity as it is considered natural. The most common smoked foods are meat and fish though cheeses, nuts and vegetables are also smoked as also beverages like tea and whisky. In Scandinavia smoking the fish is popular while in Europe and in the USA it is ham.

Hot smoking

Hot smoking foods are exposed to smoke in a controlled environment. Hot smoked foods can be reheated or cooked but they are safe to eat even without further cooking. Hot smoking is carried out in temperatures that are within the range of 52°C to 80°C. This temperature range is enough to cook foods fully and yet retain the moisture and flavour. If the temperature goes beyond 85°C foods can shrink since both moisture and fat can be dried away. Smoke roasting and smoke baking are two processes that combine hot smoking with roasting and baking. This process can be carried out in closed wood fire pit.

Cold smoking

Cold smoking is used more as a flavour enhancer. It is used specially for cold smoking pork chops, beef steaks, chicken breasts, salmon and scallops. The temperatures used for cold smoking are between 20 to 30°C when done in a smokehouse. This temperature is enough to retain moisture in foods and does not cause the meats to harden but provides a surface which smoke can easily penetrate for the smoked flavour.  However, cold smoking alone is not sufficient for preserving food as cold smoking does not cook foods.  Since meats will not cook fully so before cold smoking, meats need to be cured. Curing meats removes moisture required by bacteria to grow. The smoke also works as a barrier to prevent bacteria growth.

Health concerns

Smoked foods must be eaten sparingly as smoked, cured and salted meats are seen as stomach cancer risk. Smoking can create compounds like polycyclic aromatic hydrocarbons, or PAHs which are considered carcinogens.