On food and cooking the science and lore of the kitchen ( PDFDrive ) 1193

separating, or the proteins coagulating and
curdling.
Wholemilkisonlyabout4%fat,soitsfat
globulesaretoofewandfarbetweentoblock
theflowofthewaterphaseandgivemuchof
animpressionofthickness.Creamisaportion
ofmilkinwhichthefatglobuleshavebeen
concentratedandcrowded:lightcreamis
around18%fat,andheavyorwhippingcream
around38%.Inadditiontoitsfatsupply,
creamoffersproteinsandemulsifying
moleculesthatcanhelpstabilizeother,more
fragileemulsions(beurreblanc).
Heavy Cream Resists Curdling The casein
proteins in milk and cream are stable to
boiling temperatures, but they’re sensitive to
acidity,andthecombinationofheatandacid
will cause them to curdle. Many sauces
include flavorful acid ingredients: sauté pans
are often deglazed with wine, for example.
This means that most milk and cream


products, including light cream and sour
cream, can’t actually be cooked to make a
sauce; they must be added as a last-minute
enrichment. The exceptions are heavy cream
and crème frche, which contain so little
caseinthatitscurdlingsimplyisn’tnoticeable
(p.29).
ReducedCreamWhenheavycreamisadded

toanotherliquidtoenrichandthickenit—to
a meat sauce, or deglazing liquid, or a
vegetable puree — then of course its fat
globules are diluted and its consistency thins
down. In order to make cream a more
effective thickener, cooks concentrate it even
further by boiling off water from the
continuousphase.Whenthevolumeofcream
is reduced by a third, the globule
concentration reaches 55% and the
consistency is like that of a light
starchthickened sauce; when reduced by half,
the globules take up 75% of the volume and