What are some important technological advances affecting food preparation.

There are, of course, tons of these, depending on how far
back you want to go.  To me, the most important technological advance affecting food
preparation is the electric stove and oven.  I cannot even imagine how much harder it
was to cook back in the days of wood stoves or even before
that.

This is especially true of the oven.  Nowadays, our
recipes are really specific about temperatures.  For example, when I make bread, I bake
it at 400 degrees for a while and then turn it down to 325.  If all I had was a wood
oven, I can't imagine how I would even know what 400 was, let alone trying to turn it
down to 325.  It must have been so much harder to bake back
then...