Starter cultures

Many fermented foods can be manufactured merely by allowing microorganisms already present in the environment to act on a foodstuff. An example of this is in the agricultural manufacture of silage (fermented cut grass used for winter feeding of cattle). In the absence of air the acidification of grass will occur as microorganisms on the grass slowly convert carbohydrates into organic acids. However, there is a significant danger that pathogenic Bacteria or toxins will build up during the fermentation, so starter cultures containing Enterococcus, Pediococcus, and Lactobacillus are grown up in the laboratory and mixed with the grass as it is cut. The presence of the large amounts of starter culture increases the speed of the fermentation and reduces the incidence of contamination as the starter culture out-competes endemic microorganisms.

The principle of using starter cultures is employed in the large-scale manufacture of beer and wine, where the brewer or vintner has a choice of Saccharomyces strains (yeast) that will give particular flavors distinct to different types of beer or wine.