A maturing sausage is one that has been cured over a period of time to achieve a smooth texture and a rich flavor. It may be dry cured or smoked, or a combination of both. The process of making a maturing sausage involves several hurdles, each of which has an effect on the flavor and quality of the finished product.
Lowering the pH of the meat is a primary hurdle against bacteria growth. This is achieved by adding fast acting sugars and/or GDL (glucono-d-lactone).
The choice of starter cultures and the initial fermentation temperature are important for achieving the desired fermentative results. These can range from very fast cultures targeted for fermentation temperatures up to 45o C, through medium cultured which are usually targeted for fermentation temperature of 26 o -30 oC and through slow cultured which are normally targeted for fermentation temperatures of 90o -115o F and up.
Salt and Sodium Nitrite are added during the fermentation stage to inhibit the growth of harmful bacteria that can spoil the meat. These additives must be applied in the early stages of fermentation, and not later as they can impede the development of beneficial microorganisms that will help to stabilize the meat.
At the beginning of the fermentation phase air speed is increased to about 0.8 m/sec, to allow for fast removal of moisture from the surface of the sausage. This also helps to prevent the casing from hardening.
After about 48 hours the fermentation phase ends and drying starts. The Aw of the meat is lowered to about 0.85-90%. As this happens it is possible that the air flow is maintained to permit the faster removal of moisture from the surface but it could be difficult to remove the remaining amount of water.
It is important to lower the humidity again at this stage to be about 75% and that will decrease the moisture content of the sausage even more. This will allow the mold to develop which is necessary for oxidation and flavor development to take place.
The mold grows on the outside of the sausage in the form of a powdery white coating which is known as mycelium. Mycelium is harmless and is present in most dry cured sausages, though it is not always visible.
As the mycelium grows it is encased in a layer of calcium carbonate that creates a tough outer shell on the sausage which is called the caulk. This layer is a barrier to the growth of harmful bacteria and helps to keep the sausage moist.
The sausage is placed in a chamber for a period of 4-6 weeks at this stage. It should not be dipped in any liquid as it will promote the growth of unwanted bacteria and this can lead to mold.