On Food and Cooking

the major milk protein, casein, when milk is
heated. If the fat globules account for 25% or
more of the cream’s weight, then there’s a
sufficient area of globule surface to take most
of the casein out of circulation, and no casein
curds can form. 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.)

Kinds   of  Cream

U.S.    TermFat Content,    %Use

Half-and-half12 (10.5–18)Coffee,    pouring

12–

30

Coffee, pouring,    enriching   sauces,

soups,  etc.,   whipping