Compound Interest: The Chemistry of Camembert

The Chemistry of a Camembert — Click to enlarge

The creaminess of camembert is bested by few other cheeses – but it also has a strong smell to rival blue cheeses that reminds you of its presence in your fridge! Additionally, unlike many other cheeses, as it’s left for longer its insides start to become more gooey. Here we take a look at some camembert chemistry, and try to uncover the chemical reasons behind the cheese’s unusual characteristics.

Camembert is a surface-ripened cheese; other surface-ripened cheeses including brie, cambozola, and a number of goat cheeses. Hard cheeses ripen internally, as a result of a number of processes involving milk and microbial enzymes. However, surface-ripened cheeses, as the name suggests, ripen from the outside in, with the hard outer rind of the cheese actually consisting of a layer of mould which facilitates this process.

In the case of camembert, after the cheese is made, it is commonly sprayed with the mould Penicillium camemberti and/or Geotrichum candidum. The growth of these moulds is what gives the cheese its mottled white appearance. The mould works its magic on the cheese for a minimum of three weeks, ripening the cheese and developing its flavour. This ripening process continues whilst the cheese is in its packaging, and can also help explain camembert’s increasing ooziness as it ages.

The cow milk that camembert is made from contains the sugar lactose, which is transformed by bacteria in the cheese into lactic acid. The surface moulds on the camembert can break down this lactic acid into carbon dioxide and water, which reduces the acidity of the cheese around the surface. This creates a concentration gradient, leading to more lactic acid migrating through the cheese towards the surface, where it too is broken down, and so the cycle continues.

After a while, the unequal pH in the various parts of the cheese starts to affect its structure. As the lactic acid is broken down, the pH at the surface changes from around 4.6 to up to 7.0. This pH change affects the solubility of calcium phosphate.

Calcium phosphate is found in cow’s milk, and therefore in cheese; within the cheese it helps hold together clusters of milk casein proteins called micelles. Calcium phosphate’s solubility drops as the pH of the cheese increases, so it begins to precipitate near the surface of the cheese. This then leads to a concentration gradient in the cheese that draws more calcium phosphate from the cheese’s centre. This is a significant factor in the softening of the cheese.

How about camembert’s smell? This is contributed to by a wide range of compounds, many of which are produced as a consequence of the ripening process. They include such delights as isovaleric acid, which in isolation smells of cheesy feet, diacetyl (buttery), methanethiol (cabbage-like), methanol (boiled potatoes), 1-octen-3-one (mushroom-like), and butyric acid (sweaty). Of course, though some of these sound pretty unpleasant in isolation, they come together to contribute the characteristic camembert smell.

Another compound that can make a significant contribution to camembert’s aroma is ammonia. This is produced by the deamination of amino acids on the cheese’s surface. The amount of ammonia increases as the cheese ripens; after a significant amount of time, the smell can become very strong, at which point the cheese is probably past its best!

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