The white mold used in Brie and Camembert greatly affects how the texture of the cheese changes while it ages.
This post may seem too specific to have any use to anyone, but I assure you the chemistry is interesting enough to make up for it. How many times have you cut a wheel of Brie/Camembert open to be met with a ring of translucent gooey goodness with an opaque chalky center? Quite often I’m guessing. How many times has a consumer done this and assume something is wrong with the cheese? Probably just as often unfortunately.
Many a cheesemonger know this is the normal progression of many white mold cheeses. But what exactly is going on? What’s the difference between that gooey perimeter and chalky center? These textural differences are a hallmark for Brie and Camembert.Top
Lactate is the conjugate base of lactic acid. A “conjugate base” is just a fancy way of saying a de-activated acid; an acid that’s lost its pep. The structure of lactate and lactic acid only differ by one proton (a positively charged hydrogen atom). This missing proton is what, by definition, makes lactic acid an acid. For simplicity sake, we’re going to be using lactic acid and lactate interchangeably. To some chemists, that would earn me a place in the 8th circle of hell. For our purposes, the difference isn’t important.
You may remember that lactic acid is the main compound produced by starter culture when they breakdown lactose. We’ve covered this concept in previous posts. This lactic acid is then metabolized by a whole host of other microbes. The growing yeasts and molds on the surface of cheeses like Brie and Camembert convert lactate into compounds such as CO2, O2, and H2O. This causes the pH of the cheese to rise, or in other words, for the acidity level to go down. Molds like P. camemberti also metabolize the amino acids present (from the protein) and that also has a multitude of effects on pH, flavor, texture, etc. We’ll dive into some specific reactions involving pH, protein breakdown, etc. in the next few sections.Top
As we alluded to in the previous section, the metabolism of white molds causes the surface pH of Bries/Camemberts to rise. This pH rise is also affected by proteolysis which can produce ammonia (NH3), which we’ll discuss in the next section. Since the mold’s activity is on the surface, and not the interior. A pH gradient is established. With low pH (high acid) on the interior and high pH (low acid) on the surface.
This increase in pH at the surface softens the structure by affecting how proteins bond and associate to each other. The altered protein-protein interactions also give it a translucent/gooey appearance as opposed to the chalky center. This increase pH may also affect enzyme activity, such as proteases like plasmin and rennet, which is an explanation of how soupy these cheeses can become; simply, the protein structure is being breaking down by enzymes.Top
Proteolysis is the break down of protein. Since protein is the structure of cheese, it breaking down means the cheese gets softer. The white molds produce enzymes near (~1-5mm) the surface that cause proteolysis. As this happens, ammonia (NH3) can be release, which is an aroma we are all familiar with when it comes to Brie/Camembert. It is thought that the enzymes produced by the molds don’t travel that far into the cheese, so the softening of the interior is more likely caused by the effects of pH as discussed above and precipitation of calcium phosphate as discussed below.
As acid is produced in cheese, the pH lowers and calcium is dissolved from the protein structure. Calcium is basically the glue that holds cheese protein together. Without it, they can get very soft.
In white mold cheeses, the pH rises at the surface and this causes calcium to precipitate and form calcium phosphate (Ca3(PO4)2). As with pH, a gradient is formed with high amounts of calcium phosphate precipitated/crystallized on the surface and low amounts in the center.Top
I know this post was pretty jargon heavy. At the end of the day, all you need to know is: the ring around your Camembert is caused by the white mold creating various gradients in the cross-section of the cheese. The mold is changing the pH and producing enzymes, thereby affecting the texture of the cheese from the outside moving in.
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