Calcium & pHScience Byte
Calcium content of some cheeses correlates to their acidity/pH
We’ve already discussed, at some length, the importance of calcium in cheese. You may recall that calcium is the “glue” that holds cheese structure together. You may also recall that the chemistry gets quite complex when you consider calcium phosphate, buffering potential, mold metabolism, and a whole multitude of other things. This post tries to summarize what we’ve already learned and present it in a graphical form.
We’ve learned that acid is the solvent that dissolves calcium “glue” from cheese. We’ve also learned that acidity is expressed in terms of pH. With these two facts we should be able to correlate a cheese’s calcium content and pH, n'est–ce pas? If we hit the books we can find some studies where they did such a thing. For example, cheeses with a high pH (low acidity) often have a higher calcium content (see the table below). There are definitely some exceptions to this.
|Queso Fresco (adjusted)||6.2||1200|
|Queso Fresco (actual)||6.2||700|
It’s difficult to glean any information looking at these numbers in tabular form. When shown in graphical form, trends are clearly discernable. Trends have been color coded. Read below the graph to learn more!
Below are brief descriptions about the various cheeses on the graph (color coded).
Main Sequence Cheeses
These cheeses follow a general trend of “lower pH leads to lower calcium”. Another way of putting that is “more acidity means less calcium” (since acid dissolves the calcium from the cheese structure). If you like astronomy like I do, you'll recognize that I stole the "main sequence" moniker from the Hertzsprung–Russell diagram.
Latin American Cheeses
Here, Queso Fresco is shown as matching up with the trend shown by the “main sequence” cheeses. In order to accomplish this the calcium level had to be calculated based on the solids content of Queso Fresco, compared to that of Cheddar, Swiss, etc. Since Queso Fresco has such a high moisture content (~50%), the calcium is, in-essence, diluted out and wouldn’t fit so nicely on the trend if mathematical adjustments weren’t made. If you’re curious about the exact math, drop me a line.
Why doesn’t Parmesan fall nicely in the trend? A few things are at play here. For one, this cheese is called a “sweet make”. This means not much acid is produced before rennet addition, leaving much of the calcium bound to the cheese structure. As the cheese ages, acid being produced by the starter culture will dissolve some calcium, but not nearly as much as it would have in the liquid milk. The other main factor is how low in moisture Parm is. This lack of water has the reverse of the dilution effect we discussed for the Queso Fresco. Would Parm fit nicely in the trend if we adjusted its calcium content based on moisture content? You betcha!
Many thanks to Dean Sommer (of CDR) for helping me understand this!
Astute individuals may notice that cream cheese and cottage cheese have really low calcium content. What’s going on here? Cream cheese and cottage cheese are both examples of acid-set/lactic curd cheeses. These cheeses are usually acidified over long periods of time leading to much of their calcium being removed.
Perhaps the most confusing part of the graph are the blue/white mold cheeses hanging out all by their lonesome. They don’t even come close to following the trend, what the hell? Up to this point I haven’t mentioned a really important piece of information, all of these pH values are final measurements. Blue cheese and bloomy cheeses often end up at a pH ~ 6.2-6.5, but start their lives at low pHs around 4.6-4.9. When the cheeses first reach these low pH values, all that calcium is dissolved. With this piece of information, it becomes apparent that, at day 1, these cheeses match the trend. It is only through the metabolism of the mold that the pH goes up (acidity goes down) and they no longer follow the trend.Disclaimer
Calcium content and pH can vary wildly in cheese. The values and calculations used in this post are approximations and highlight a general trend.
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