Fermented sausages are cured using the same principles as other cures – sugar is fermented by bacteria in an anaerobic environment to produce acid, which lowers pH of the sausage to at least 5.3, but more typically between 4.6 and 5.0. There are two basic types of fermented sausage, semi-dry and dry-cured, classified by how much original moisture they have lost in the curing process.
In general, beef is preferred for semi-dry sausages, while pork is used for dry sausages. All meat should be trimmed of fat and sinews. Removing any soft intramuscular fat is especially important. The meat is then chopped to a desired consistency and blended with spices or herbs. A small amount of sugar is typically added to aid in the production of lactic acid. Salt (both curing salt and regular salt) is added last.
After mixing, the meat is stuffed into casings. It’s important to make sure that air pockets do not form, which will trap oxygen in the sausage and threaten the fermentation stage of the cure. The sausages are then air dried for a short period to enable any surface moisture to escape. If the environment is too humid, the surface of the sausage will turn slimy. But if it’s too dry, the skin will crust over and become unable to accept smoke properly.
The goal of drying a sausage is to dry it from the inside out. Dry too fast, and a protein crust on the surface prevents interior moisture from escaping. Too slow, and you risk yeast and mold growth on the surface. At the beginning of the drying process, the relative humidity of the air should be kept high, as high as 98%. As the aging continues and the water activity value of the sausage drops, the humidity of the air must be lowered, though some producers tolerate a bit of mold in the beginning stages to help evaporation at the center of the sausage, and wash it off at the end. The relative humidity of the drying chamber should be kept 3-5 points below the interior moisture. Maintaining light air circulation helps as well.
Semi-Dry Sausage – Includes summer sausage, some cervelats, metwursts, and American bologna. The length of production is short, usually just a few days. Semidry sausages are usually stuffed in medium or large diameter casings. Their pH is usually between 4.8 and 5.2, with water loss around 15%. These are regularly smoked, usually below 45C. Semi-dry sausages usually use finely chopped meat.
Dry Sausages – The pH level in a dry sausage is typically higher than a semi-dry, between 5.0 to 5.3 or 5.5. After dropping sharply in the beginning of the aging process, the pH level in a dry sausage will slowly rise in a long age, affecting the flavor. Water loss can account for 20%-40% of the original weight. Dry sausages tend to use more coarsely chopped meat. Most dry sausages are cold smoked between 12C and 18C. Salamis are popular dry sausages.
Smoking Cured Sausages
Many cured sausages are also smoked. A well-designed smokehouse will distribute heat and smoke evenly, which requires controlling circulation, temperature, and humidity. Typically hardwood is used as fuel for creating smoke.
Semi-dry and dry sausages are smoked in very different conditions. Depending on the diameter of the sausage, smoking may last anywhere from 10 to 40 hours for small diameter sausages, to 1-3 weeks for exceptionally thick sausages. Semi-dry sausages are typically smoked at higher temperatures (22-32C), though some temperatures go as high as 60C to improve flavor and limit growth of bacteria. For a dry smoke, the optimal temperature is considered to be 14C, and a temperature of 31C is never passed.