Fermented sausage is a type of sausage that has beneficial bacteria and other additions to the meat that allow it to age and air dry without spoiling. The fermentation process develops the flavor of the sausage as water inside the meat dissipates and the acidity level rises. Common types of fermented sausage include salami and chorizo. While the sausage can be smoked to add more flavor, most are not. The successful production of fermented sausage relies on a good knowledge of food science and experience with the process so problems can be quickly identified and resolved before the sausage becomes rancid.
The first and most important step in making fermented sausage is to ensure that all the equipment used is sterile and clean. All the work surfaces and the area of production also should be very clean. This is to ensure that as few harmful bacteria as possible are present, reducing the chance that they will enter the meat, although some inevitably will.
The meat used must be fresh. This is because meat that is not fresh will have a wide array of harmful bacteria inside, increasing the chances that it will spoil instead of fermenting. Although a fermented sausage can be made of nearly any type of meat, pork and beef are two of the most popular choices.
The ground meat is mixed with salt and, in many cases, nitrates in preparation for fermentation. The salt will help to kill some bacteria, while the nitrates will provide an incentive for good bacteria to arrive and grow inside the sausage. The beneficial bacteria will convert the nitrates into nitrites and, in the process, also consume many of the bacteria that could lead to food poisoning or spoiling of the meat.
The ground meat is stuffed into sausage casings that are water permeable and then hung up to air dry. The goal is to allow the fermentation process to take effect without the meat spoiling. Two things will occur if enough beneficial bacteria are inside of the meat. The first is that the water content of the fermented sausage will decrease, causing it to dry out to some degree, although some water is retained by different elements in the meat.
The second thing to occur is that the acidity level will rise inside the sausage. A high acidity level will help to destroy harmful bacteria. Beyond a certain level of acidity, the fermented sausage will become stable and be ready for packaging and consumption once it has aged enough to provide the desired flavor.