"Edkins, Suzanne M" <Suzanne.Edkins@med.va.gov> wrote:
>I was really just interestd in the answer to the question. My niece is
>using yeast in a science experiment and this question came up. I said too
>much will make the bread rise too much, others says it makes it fall. I
>think we are argueing symantics. I think it falls after the dough rises
>too much because it gets too heavy or explodes. Help. Any thoughts.
OK- the reason bread rises is that the stretchy dough acts like a balloon
and traps the gas formed by the yeast. Reasons for bread flopping can
include a dough which isn't stretchy enough (so the gas escapes), dough
which is too thick (so the balloon can't get blown up) and dough which is
too thin (so the gas escapes).
To much yeast will have no effect whatsoever as long as you watch your
bread, and knock it down and bake it when it is the right
shape/size.... If you leave bread too long rising so that the dough has
stretched 'thin' the gas can escape when you move the bread into the
oven. The 'balloon' deflates and you get a flat loaf. In our house, if we
leave bread to rise a little too long, we just get loaves that have puffed
up above the loaf tins so that they look like a type of mushroom. They
don't flop, though....
If you really leave bread for ages in the first rising, and the knock it
back, you can sometimes have a situation where the yeast won't grow any
more. This can be because it has given off too many waste products
(alcohol, carbon dioxide etc.) into the dough which then slow it down to
the extent that you won't get any rising. This can be another cause of
flopping, and can be related to using too much yeast.
HTH, and that other techies will correct anything I've got wrong.
Lorna
--
Lorna Campbell
Strathbungo
Glasgow
Scotland