and above — right around the temperature at
which the egg proteins are bonding to each
other — the granules absorb water, swell up,
and begin to leak their long starch molecules
into the liquid. The swelling granules slow
protein binding by absorbing heat energy
themselves, and the dissolved starch
molecules get in the proteins’ way and
prevent them from bonding to each other too
intimately. Because they contain starch, both
chocolate and cocoa can also help stabilize
custards and creams.
A full tablespoon/8g of flour per
cup/250ml liquid (or 2 teaspoons/5g pure
starch in the form of cornstarch or arrowroot)
is required to prevent curdling. The
disadvantage is that this proportion of starch
also turns a creamily smooth dish into a
coarser, thicker one, and diminishes its flavor.
Custard Theory and Practice