Smoking meats and fish is a way of flavouring them, or helping to preserve them, or both.
The meat or fish is first cured in salt, either “dry-cured” by having salt rubbed into it and let stand, or “wet-cured” in a brine. The salting before smoking is necessary because the meat or fish will have a lot of time during the smoking process when the temperature is just right for bacteria to grow and spoil the meat or cause food poisoning. Bacteria can thrive between 40 F and 140 F (4 C and 60 C.)
The item is then smoked. The heat from the smoke dries the surface of the meat, making it less moist and inviting to bacteria (even though people only recently learned what bacteria are, of course.) Beyond that, smoke has chemicals in it (such as phenols, ketoses, carbolic acids) that in addition to giving the meat a smoky flavour, inhibit the growth of bacteria. In smoking, care has to be taken with the type of wood used and in maintaining the fire to get the right amount of smoke at the right temperature, so that the meat or fish doesn’t taste awful or get bitter.
Many different types of wood can be used to make the smoke: among the more popular still are hickory, apple, and maple. Fatty meats and fish are considered better for smoking than lean meats and fish because the fat will absorb the smoke and the flavour better, and prevent the item from drying out and getting tough during the smoking process.
Curing and smoking meats are no longer strictly necessary. We can keep everything refrigerated and buy fresh meat whenever we like. People got to like the smoky taste so much, however, that smoking is now done mostly for the taste.
There are two types of smoking, “cold” and “hot.”
Cold smoking is basically a drying process that adds flavour and colour. The fire producing the smoke is maintained at a low temperature — usually less than 100 F (38 C), but opinions vary — for an extended period of time of several days or even weeks. A temperature of over 120 F (49 C) starts meat cooking, and cooked meat won’t keep as well. Cold smoking is generally used on foods that will be cooked afterward, with notable exceptions such as salami, pepperoni and salmon.
Hot smoking is basically a flavourful cooking method. The meat or fish is smoked at a higher temperature between 100 F / 38 C and 180 F / 82 C (will go as high as 225 F / 107 C, if the person is planning to eat the item right after smoking.) The flesh of the item being smoked gets partially cooked. Hot smoked fish generally doesn’t need additional cooking before eating it. Hot smoking is the smoking method most often used by home enthusiasts, as it is the easier temperature range to maintain.
In German, “Heißräuchern” means “hot smoking”; “Kalträuchern” means “cold smoking.”