Yeast is the driving force behind fermentation, the magical process that allows a dense mass of dough to become a well-risen loaf of bread. And yet yeast is nothing more than a single-celled fungus. How does it do it? Yeast works by consuming sugar and excreting carbon dioxide and alcohol as byproducts.Click to see full answer. Thereof, how does the amount of yeast affect bread?One gram of yeast contains 20 billion tiny cells. This can affect the bread by adding a “yeasty” taste if you put too much into the dough. General amounts of yeast are around 1 – 2 % of the flour, by weight. Too much yeast could cause the dough to go flat by releasing gas before the flour is ready to expand.Beside above, what happens if you put too little yeast in bread? Adding extra yeast in bread can cause it to rise too much and produce large holes. Whether there is too much yeast in pizza dough or too much yeast in dough to be used for other purposes, it can result in a disappointing end product. Consequently, how is yeast used in bread? Yeast in bread making Yeast is used for the leavening of bread. Yeast uses the sugars and oxygen in dough to produce more yeast cells and carbon dioxide gas. This is called multiplication. The carbon dioxide makes the dough rise which gives the bread a light and spongy texture.What happens to bread without yeast?If you don’t use yeast or other leavening in your bread dough, the bread will be dense and will not rise. As others have said, there may well be a subtle taste difference since yeast forms carbon dioxide gas and alcohol. There are many breads that are unleavened and most are flatbreads.