Often times, people think of mold on their food as something to be avoided (funky cheese-lovers excluded). The same goes for bacteria in ones' food. This is because spoilage is often associated with mold and bacteria.
Mold Use in Food
Aside from causing spoilage (notably black and green molds), mold has proven to have practical uses, such as in the development of penicillin. When it comes to food preservation, mold is found most frequently in charcuterie, in the production of various preserved meats. Some cheeses also make use of molds to impart signature colors and flavors. These molds are taken from the Penicillium family.
The purpose of molds in food preservation are manifold. The first is to protect the food's surface from other organisms that may be present, including yeasts, bacteria, and other (and unwanted) molds.
The second is to increase the pH as a finishing step. This helps to reduce the sour flavor imparted by Lactobacillus during fermentation.
Lastly, the mold coating helps to control the drying process by reducing the amount of moisture lost near the surface, compared to the inside.
These molds often impart a white coating to the meat or cheese. The white stuff on the outside of brie? A beneficial mold.
Bacteria Use in Food
As mold serves to protect the outside of a cured meat product, bacteria helps to protect the inside.
The most common bacteria used in meat starter cultures are drawn from strains of Staphylococcus and Lactobacillus.
Staphylococcus is used primarily as a way to improve the color in a good, making it less like to turn a sad, unfortunate grey color, despite still tasting good. Presentation is important, folks.
Lactobacillus is useful in that it ferments sugars into lactic acid. This acid, as noted in my write-ups of various pathogens, is particularly useful in preventing contamination. In the way vinegar helps to preserve pickles, this lactic acid lowers the pH of the meat, to aid in preservation. Outside of its use with meats, Lactobacillus is most well known for its role in the production of sauerkraut. It also serves a secondary function, in that it serves as a competing organism to less desirable bacteria.
In conclusion, the use of mold and bacteria in foods is something that has, and continues to be done.
A word of caution, when using bacteria and mold cultures, make sure that you are getting them from a reliable source. Some strains of the Staphylococcus used in sausage-making can be harmful if not checked beforehand. A reputable supply store will be able to provide a verified starter culture.