Because of the way it’s made, mascarpone is considered by some to be more like yogurt than a real cheese. These folks have sort of a point, since the process for making mascarpone is nearly identical, save for the fact that mascarpone doesn’t need to be fermented after it’s been heated. It thickens up all by itself. That begs the question: why? Well let’s see now…
If you’ve ever made yogurt before you may recall that yogurt is made from low-fat milk. The milk is heated to 190 or so degrees, then cooled down to about 120. At that point a fermenting culture is introduced and the temperature is held there for several hours to give the culture time to grow and produce lactic acid. As the acid level rises, the proteins that were uncoiled by the heating process start to become attracted to one another, and eventually bond together to form a molecular mesh that traps other molecules like fish in a net. What results is a delicate gel made mostly of water molecules with a little fat and protein mixed in.
Mascarpone starts out the same way, only it’s made with high-fat cream. As with yogurt, the dairy is heated to about 190, a which causes proteins in it to unwind from bunchy yarn-like clumps into long, stringy structures. At that point acid is introduced to the cream, and here is where the two processes start to diverge. For instead of a gentle dose of lactic that causes the proteins to bond to one another, a larger dose of a stronger acid goes in. This causes the proteins to coagulate — essentially clump back up again — but because they’ve been unwound first, they trap other nearby molecules between them as they re-tangle. As the proteins are drawn more tightly together, the larger fat molecules become trapped, but smaller water molecules get squeezed out, like water from a sponge. What do you have in the end? Agglomerations of fats and proteins (curds) and water with residual fats, proteins and other molecular flotsam (whey).
So on the one hand we have a concentrated mass of dairy fat and protein, further concentrated by the elimination of some of its water. On the other we have a gel of mostly water with trace elements of protein and fat. I know which one I’d rather spread on my morning toast, but I’ll leave that to you to figure out.