Technical Snippet: How does adding starter culture affect your cheese?
Bacteria in the form of starter cultures are added to milk to make cheese. Bacteria obtain their nourishment by secreting enzymes that dissolve the food in the milk e.g. that food being fats, proteins and sugars. The nutrients are then taken in through the bacterial cell wall as a solution. The nutrients are used as a source of energy for the bacteria to multiply into more bacteria. During metabolism, energy is utilised and the waste products in the form of lactic acid are produced and are excreted from the cell. So, as cheese is being made in the vat, and after hooping, more food can be dissolved, more bacteria produced and more enzymes and acid result. The more diversity in the bacteria types that you add to the milk, the more diversity in the enzymes that are produced. This will, in turn, be beneficial to flavour development in the cheese.
The bacteria in the cheese eventually die due to a combination of time, the loss of moisture, the acid produced and the salt. The enzymes however remain in the cheese and continue to breakdown the fats, proteins and sugars in the cheese over the life of the cheese. The more bacteria you add to the milk the more lactic acid is produced and the more enzymes that are produced. But more is not necessarily better for both enzymes and lactic acid. The right amount of both is required to make a good cheese. The simple solution is simply following the dosage instructions for the recipe. However, lots more elements that affect cheese quality come into play.
During the process of metabolism:
- Proteins can be broken down by enzymes into amino acids
- Fats are broken down by lipase enzymes into fatty acids.
- Carbohydrates (milk sugar is called lactose) are broken down to lactic acid.