Propionic bacteria create holes in Swiss cheese.
Propionic bacteria are a largely harmless class of bacteria that are often found in human skin. However, these bacteria can aggravate skin conditions such as acne. Members of the propionic bacteria class are also responsible for creating the holes in Swiss cheese. The holes are the byproduct of a process in which the bacteria oxidize lactic acid and release carbon dioxide.
Propionibacterium acnes
Propionibacterium acnes is a strain of bacteria that resides in human skin. This bacterium is considered relatively harmless; however, overgrowth of the bacteria can lead to acne. Propionibacterium acnes feeds on fatty acids within the pores of the skin. When too much of this bacterium is present, it secretes chemicals that break down pore walls. The breakdown causes a skin infection that leads to acne. This bacterium can be killed with antibiotics in the tetracycline group.
Propionibacterium shermanii
Propionibacterium shermanii is a strain of bacteria that can be used to create the holes in Swiss cheese. This bacterium reacts to lactose, producing propionic and acetic acids. As a byproduct of the chemical reactions between the bacterium and lactose, carbon dioxide is released. The carbon dioxide causes the cheese to bubble; the bubbles become holes as the cheese hardens. The propionic acid itself adds a sharp flavor to the cheese.
Propionibacterium freudenreichii
Propionibacterium freudenreichii is another bacteria used in the production of Swiss cheese. Unlike shermanii, this bacterium is found naturally in milk products and needn't be introduced by the cheesemaker during the fermentation process. The mechanism by which it contributes to the flavor and appearance of the Swiss cheese is similar to that of shermanii.
According to a French study performed in December 2008, propionibacterium freudenreichii kills colon cancer cells. Rats injected with this bacteria also appeared to generate antibodies to ward off these cells. This study was replicated in 2010 by Dutch scientists.
Tags: Swiss cheese, bacteria that, carbon dioxide, holes Swiss, holes Swiss cheese, Propionibacterium acnes
