Three main types of cheese rely on moulds for their characteristic properties: blue cheese, soft ripened cheese (such as camembert and brie) and rind-washed cheese (such as époisses and taleggio).
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 P. 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 such as beer and wine which contain mould. This also makes them attractive to bacteria, which add to the flavour.
Traditionally, inoculations of sausages with moulds were done with the indigenous biota of the slaughters. Different moulds (such as P. chrysogenum and P. nalgiovense) can be used to ripen surfaces of sausages. The mould cultures develop the aroma and improve the texture of the sausages. They also contribute to shortening of the ripening period and preserving the natural quality. This expands the shelf life of the meat product.
In the past, soy sauce has been made by mixing soybeans and other grains with a mould (Aspergillus oryzae or A. sojae) and yeast. This mixture was then left to ferment in the sun. Today soy sauce is made under controlled conditions. The key flavour ingredients formed in this process are salts of the amino acid glutamic acid, notably monosodium glutamate.