1. Lactic Acid Production: This is the most fundamental process. Bacteria convert lactose (milk sugar) into lactic acid. This:
* Lowers pH (makes it more acidic): This prevents spoilage by other bacteria.
* Coagulates (curdles) the milk proteins: This forms the solid curds, the basis of cheese.
2. Flavor and Aroma Compounds: Different bacteria produce different flavor and aroma compounds, contributing to the unique characteristics of each cheese:
* Acetic Acid: A vinegar-like sourness (e.g., some cheddar cheeses).
* Propionic Acid: A nutty, slightly sweet flavor (e.g., Swiss cheese).
* Butyric Acid: A strong, pungent flavor (e.g., some blue cheeses).
* Diacetyl: A buttery, sweet flavor (e.g., some cheddar cheeses).
3. Texture Development: Some bacteria contribute to the texture of the cheese by:
* Breaking down proteins: This can make the cheese softer or more spreadable (e.g., Brie).
* Producing gas: This creates holes or "eyes" in the cheese (e.g., Swiss).
4. Mold Growth: In some cheeses, molds are introduced intentionally. They contribute:
* Flavor: Blue cheese gets its distinctive flavor from the Penicillium roqueforti mold.
* Texture: Mold can create veins or streaks within the cheese.
Key Bacteria in Cheesemaking:
* Lactococcus lactis: The most common bacteria used in cheesemaking, responsible for lactic acid production.
* Streptococcus thermophilus: Often used with Lactococcus lactis for acidification and flavor development.
* Propionibacterium freudenreichii: Responsible for the holes and nutty flavor in Swiss cheese.
* Penicillium roqueforti: Used for blue cheeses, producing the characteristic blue veins and flavor.
Remember that the specific bacteria used and the conditions under which they are grown will significantly affect the final cheese.
