Moulds in food production

Moulds are essential components of several food products, such as some cheeses, sausages and soy sauce.

Cheese making
Three main types of cheese rely on moulds for their characteristic properties: blue cheese, soft ripened cheese and rind-washed cheese.

To make blue cheese, the cheese is treated with a mould, usually Penicillium roqueforti, while it is still in the loosely pressed curd form. As the cheese matures, the mould grows, creating blue veins within it which gives the cheese its characteristic flavour. Examples include Stilton, Roquefort and Gorgonzola.

Soft ripened cheese such as Brie and Camembert are made by allowing Penicillium camemberti to grow on the outside of the cheese, which causes them to age from the outside in. The mould forms a soft white crust, and the interior becomes runny with a strong flavour.

Rind washed cheeses like Limburger also ripen inwards, but here, as the name suggests, they are washed with brine and other ingredients like beer and wine which contain mould. This also makes them attractive to bacteria, which add to the flavour.

Meat fermentation
A wide variety of moulds (i.e. Penicillium chrysogenum and Penicillium nalgiovense) are used to ripen surfaces of sausages. The mould cultures plays a role in aroma formation and improve the texture of the sausages. They also contribute to shortening of the ripening period and preserving the natural quality and in that way expanding the shelf life of the meat product.
Inoculations of sausages with moulds were traditionally done with the indigenous flora of the slaughters, the socalled house flora.

Soy sauce
Traditional soy sauce is made by mixing soybeans and other grains with a mould – either Aspergillus oryzae or Aspergillus sojae – and yeast. Historically, this would have been left to ferment in the sun, but nowadays it is mostly made under industrial conditions. The key flavour ingredients formed in this process are salts of the amino acid glutamic acid, notably monosodium glutamate.