I am reading the part of the book "On Food" about milk cream.
There is a section that discusses the stability of milk cream in cooking.
The argument is that if the fat content of the cream is high enough (>25%) then the total surface area of the membranes that surround fat globules is quite large.
Large enough that upon heating, most of the major milk protein casein present in the cream becomes stuck to the membranes and is thus unavailable to coagulate (note that in cream the ratio of fat to protein is 10:1 versus about 1:1 in milk).
Thus, even cooking the cream with acidic or salty ingredients in a mixture, the cream does not curdle.
At the end of the section, however, there is the following snippet
At lower fat levels, there’s both a smaller globule surface area and a greater proportion of the casein-carrying water phase. Now the globule surfaces can only absorb a small fraction of the casein, and the rest bonds together and coagulates when heated. (This is why acid-curdled mascarpone cheese can be made from light cream, but not from heavy cream.)
I'd like to understand this snippet.
One wants curdling to occur when making mascarpone cheese I guess.
The process (which I googled) involves heating the cream to about 85 Celsius and then adding acid (lemon juice), letting it cool, and then leaving it for 24h or so.
With heavy cream (say, 45% fat), the heating does not curdle the cream (for the reasons in the initial argument above), and adding acid after the heating also does not curdle the cream (same initial argument: the casein proteins are all bound to fat globule membranes).
With a light cream, I guess curdling occurs due to the acid. I am not sure what the heating is for exactly. I suppose it facilitates the curdling by denaturing the proteins first?
Thus, the snippet is basically saying that if you want curdling (as in mascarpone) you need to use a lower fat content cream.
Coincidentally, yesterday I bought cream to make mascarpone, and it is 45% so shucks. The internet recipes I looked at all said to use heavy cream.
