Irwin Franzel came up with the solution when he
vacationed in Denver several years ago. He was kind
enough to allow us to reprint his advice in our book
THE BREAD MACHINE MAGIC BOOK OF HELPFUL HINTS. So to quote
Irwin and ourselves:
At higher elevations, the dough "overproofs." Due to the
lower barometric pressure at high altitudes, the carbon
dioxide gas bubbles created by the yeast expand more
rapidly. Therefore, the bread rises too high, the gluten
loses its strength, and the bread collapses during baking.
Try the following combination of suggestions:
Reduce the amount of yeast by about 1/3. This will create
less carbon dioxide and the bread will not rise as quickly.
Increase the salt by 25%. This will have the same effect
as decreasing the yeast. The bread will rise slower and be
less likely to sink during baking.
Add from 1/2 to 1 T gluten per cup of flour. Increasing
the gluten will give added strength to your bread.
Watch your dough as it mixes. You may need to add at
least 1 to 3 T more liquid since flour stored at high
altitudes tends to be drier.
Two other options: Because of the rapid-rising nature of
high-altitude breads, try baking them on the Rapid Bake
cycle of your machine to reduce the rising time. Or, if
your machine has a programmable mode, watch the loaf as it
rises; when it nears the top of the bread pan, switch to the
Bake cycle manually.
Hope this does the trick for you!