What microorganisms turn milk in to cheese?

The microorganisms that turn milk into cheese are primarily bacteria. These bacteria are classified into two main categories:

* Lactic Acid Bacteria (LAB): These bacteria are the workhorses of cheesemaking. They convert lactose (milk sugar) into lactic acid, which lowers the pH of milk and causes it to curdle. Different LAB species produce different flavors and textures in cheese. Some common LAB used in cheesemaking include:

* Lactococcus: Found in most cheeses, produces a mild flavor and helps with curd formation.

* Streptococcus: Also involved in curd formation, can contribute to buttery or creamy flavors.

* Lactobacillus: Produces more complex flavors and can contribute to the texture of cheeses like cheddar and swiss.

* Propionibacterium: This bacteria is responsible for the characteristic holes (eyes) in cheeses like Swiss. They produce propionic acid and carbon dioxide, which give Swiss cheese its unique flavor and texture.

The specific bacteria used in cheesemaking vary depending on the type of cheese being produced. Each cheese has a unique combination of bacteria that contributes to its flavor, texture, and appearance.

Here's a simplified explanation:

1. Milk is heated: This kills unwanted bacteria.

2. Starter cultures are added: These cultures contain the desired LAB species.

3. LAB convert lactose to lactic acid: This lowers the pH and causes milk proteins to coagulate.

4. Curds are formed: The coagulated milk proteins separate from the whey.

5. Curds are cut and stirred: This helps remove whey and creates the cheese texture.

6. Curds are pressed and shaped: This removes more whey and forms the cheese's shape.

7. Cheese is aged (ripened): This allows the bacteria to continue working, developing flavor and texture.

During aging, additional molds and bacteria can be added to some cheeses, further contributing to their unique characteristics.