Brewing with bread yeast

Question

recently bought northern brewer irish ale and yeast was misplaced. can I use bakers yeast? Also, how long will wort last before adding yeast?

Answer 1

Baker's yeast is a very poor yeast for brewing - prone to infection and produces poor alcohol content before dying off. Your wort should keep for a day or two if tightly covered, but if unsure, you can reboil it to sterilise before brewing.

Answer 2

There is very little difference in price compared to a big difference in results.

Bread yeast feeds on starches in the flour, producing CO₂ which expands the gluten proteins in the flour, gluten proteins cause the dough (of which flour is a main ingredient) to expand and rise. Baking removes the alcohol. Beer yeast is designed for low temperature and consists of a yeast called Saccharomyces cerevisiae (Brewer's yeast, also used for wine) or Saccharomyces pastorianus (for Lager) while Baker's yeast is a different strain; though similar to brewing yeast.

Fermentation of fruit (grapes, plums, etc.) is a faster process than the fermentation of wheat, potatoes or corn. This is because most fruits, when ripe, store carbohydrates as a monosaccharide called fructose. Yeast can metabolize monosaccharides immediately. Cane sugar (sucrose) is a disaccharide. Most species of yeast have the enzyme sucrase. Sucrase breaks sucrose into the two monosaccharides glucose and fructose. However, potatoes, corn and wheat store carbohydrates as a polysaccharide called starch. Starch is a large molecule composed of many monosaccharides linked together. Yeast cannot metabolize starch directly. The starch has to first be broken down into its monosaccharides, which are glucose. Yeast lacks the enzyme amylase that will digest starch into glucose.

In beer brewing, germinating barley is added to the fermenting wheat. The germinating barley supplies the enzyme diastase which breaks the starch into maltose, a disaccharide of glucose. The yeast can separate maltose into glucose, but the metabolism of maltose by yeast is a slow process. As the maltose is hydrolized into two glucose molecules, the glucose is then fermented into ethanol.

Wine yeast is specifically developed to produce results designed for the type of wine you are making. From ECKraus Blog - "Making Wine With Bread Yeast… Not!":

Most bread yeast will ferment alcohol up to about 8% with ease, but when trying to produce alcohol beyond this level, the bread yeast begin to struggle, very often stopping around 9% or 10%. This is short of what we’d like to obtain for almost any wine.

Another reason making wine with bread yeast is not a good idea is that bread yeast do not clear out very readily or settle very firmly, either. They typically will form a low layer of hazy wine in the bottom of the fermenter that will never completely clear out.

Even more importantly, bread yeast produce alcohol that is plagued with a lot of off-flavors. The bread yeast becomes so stressed and has to work so hard that off-flavored enzymes and fatty acids are produced along with the alcohol.

There are several other issues with using bread yeast to make your wine, but these are the big ones: the alcohol, the clearing, and the flavor.

So while Baker's yeast, used for beer, probably won't affect the strength it won't taste correct and the poor flocculation would make the resulting brew excessively cloudy.