The Importance Of Microbial Cultures In Cheese Production

Cheese is a well-known and diverse food that has been produced by nearly every culture throughout the course of human history. The microbial strains used throughout the production process are considered the best metric for categorizing cheeses. These cultures, which can include bacteria, fungi, and other microorganisms, play a vital role in the fermentation and aging of cheese. 

Most cheeses start out with pasteurized milk. Pasteurization is deemed necessary to rid the milk of any harmful bacteria or fungi that would multiply during the cheesemaking process. That said, some traditional cheeses, like roquefort and idiazabal, may call for the use of raw or unpasteurized milk. Following pasteurization, starter cultures of bacteria and/or fungi are added to the milk; these cultures ferment the lactose in the milk, producing lactic acid and other compounds that contribute to the flavor and texture of the cheese. 

There are a number of factors that determine the specific bacteria or fungi used as a starter, including the cheese's desired flavor profile, the climate in which it will be aged, and the cheese's desired texture after it has been aged. For example, the production of cheddar cheese requires the addition of starter cultures of bacteria such as Streptococcus thermophilus and Lactococcus lactis, which are used to ferment the milk and produce lactic acid. This lactic acid helps to coagulate the milk proteins, forming curds. The curds are then cut, heated, and stirred to produce a consistent texture. Cheddar is aged anywhere from six months to two years, during which additional bacteria and fungi may grow on the surface of the cheese and contribute to its flavor and texture. 

Fungi and molds, too, are used as starters in cheese production, primarily in the production of blue or cave cheeses. The best example of a cheese that depends on mold for flavor is Roquefort, which necessitates the use of a strain of mold that is unique to the cheese called Penicillium roqueforti. This fungus grows on the surface of the cheese and produces the characteristic blue or green veins that are found in blue cheese. There are a number of ways that the mold may be introduced to the cheese: as a starter prior to curdling or as an aerosol during aging. The mold typically grows on the cheese naturally, as the temperature and humidity of the caves the cheese is aged in are ideal for the growth of mold. That said, most cheesemakers introduce lab-grown cultures of the mold into the cheeses during different stages of the cheese’s production in order to ensure optimum taste and quality. Most blue cheese is aged for three to five months. During this time, the mold spreads all over the cheese, giving it a distinct smell that you can taste. 

Then scientific monitoring of bacterial and fungal strains is just as important in the production of soft cheeses such as Brie and Camembert. Starter cultures of bacteria such as Lactococcus lactis and Lactobacillus bulgaricus are added to the cheese in order to induce curd formation through the production of lactic acid. The use of microbial cultures in these types of cheese requires caution, as the higher moisture content is a sensitive variable that can easily affect the population of different strains, thereby negatively impacting taste and flavor. These cheeses can also be aged for a few weeks or months. During this time, bacteria and fungi like Brevibacterium linens and Penicillium camemberti grow on the surface of the cheese, making it taste and feel better.  

The specific strains of bacteria and fungi used in cheese production play a significant role in determining the nature of the final product. For example, the use of Streptococcus thermophilus and Lactococcus lactis in the production of Cheddar cheese gives it its distinctive sharp, tangy flavor, while the use of Penicillium roqueforti in the production of blue cheese gives it its characteristic blue or green veins and a strong, pungent flavor. The texture of the cheese can also be affected by the microbial cultures used. Some cultures make cheeses that are softer and creamier, while others make cheeses that are harder and more crumbly. 

Almost all traditional cheeses rely on additional microbial cultures introduced naturally during the aging process. For example, the bacteria Brevibacterium linens, which is found on the surface of some washed-rind cheeses, produces compounds that contribute to the rounds' pungent, earthy flavor. In the same way, the fungi Penicillium camemberti and Penicillium candidum are often used to age soft cheeses like Brie and Camembert. These fungi help give these cheeses their creamy texture and white, edible rind.