On food and cooking the science and lore of the kitchen ( PDFDrive ) 1497

evaporate moisture continuously. Cooks take
advantage of it when they bake delicate
preparations like custards gently by partly
immersing the containers in an open water
bath, or oven-roast meats slowly at low
temperatures,orsimmerstockinanopenpot.
In each case, evaporation removes energy
fromthefoodoritssurroundingsandcausesit
tocookmoregently.
Steam Releases a Lot of Heat When It
Condenses into Water Conversely, when
watervaporhitsacoolsurfaceandcondenses
into liquid water, it gives up that same high
heat of vaporization. This is why steam is
such an effective and quick way of cooking
foodscomparedwithplainair—alsoagas—
at the same temperature. We can put a hand
intoanovenat212ºF/100ºCandholditthere
for some time before it gets uncomfortably
warm; but a steaming pot will scald us in a
secondortwo.Inbreadbaking,aninitialblast


of steam increases the dough’s expansion, or
ovenspring,andproducesalighterloaf.
WaterandAcidity:ThepHScale

Acids and Bases Despite the fact that the
molecular formula for water is H2O, even
absolutely pure water contains other
combinations of oxygen and hydrogen.

Chemicalbondsarecontinuallybeingformed
and broken in matter, and water is no
exception. It tends to “dissociate” to a slight
extent,withahydrogenoccasionallybreaking
off from one molecule and rebonding to a
nearbyintactwatermolecule.Thisleavesone
negatively charged OH combination, and a
positively charged H3O. Under normal
conditions,averysmallnumberofmolecules
existinthedissociatedstate,somethingonthe
orderoftwoten-millionthsofapercent.This
is a small number but a significant one,
because the presence of relatively mobile