How much yeast should you use?
One gram of yeast contains 20 billion tiny cells. There are about 7 grams in a quarter ounce package that we buy at the store (2 1/2 teaspoons). That's 140 billion cells!
When I started baking as a girl, we used one packet active dry yeast for two loaves of white bread. Then it became trendy to use two packets because the bread rose faster. We thought we were onto something. What we were onto was making the yeast companies rich! They convinced us that bread had to rise rapidly, but the faster that happened, the fewer by-products the yeast produced and the less taste the bread had. We made up for that by adding oils, sugar, eggs, you name it. But bread does not need to be finished quickly. If we start with less yeast, we have slower rising times and a larger window of opportunity in which to finish the bread.
When you start making bread, add the amount of yeast called for in the recipe. If it tastes good and has the properties you want, then stick with it. I have started cutting the amount of yeast in half in many recipes with little change in rising time. This is partly because I am using the instant yeast, which reactivates very quickly and is more concentrated. That's also because half of 140 billion is still 70 billion little factories building gas and alcohol in my dough!
Because yeast does not divide much in bread dough (only 20-30% increase in cell numbers in 4 hours), what you start with is about what you end up with in terms of yeast numbers. This can affect the bread by adding a "yeast-y" 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.
If you let the dough rise too long, it will start having a yeast or beer smell and taste and ultimately deflate or rise poorly in the oven and have a light crust. This is not because of huge numbers of yeast cells taking over, but due to too little residual sugar and the inability of the gluten to stretch any further.
Why do some recipes call for just a pinch of yeast?
Some recipes start with a quarter teaspoon of yeast, that is just 10% of a packet of yeast! These recipes are depending on long fermentations to create flavor and mostly start with a very wet dough. This lets the yeast move around and divide while the flour enzymes are doing their thing. A dough like this is usually fermented overnight and often stirred into a final dough with more yeast to aid in the final rise.
What are the differences between regular yeast, instant yeast and bread machine yeast?
Taste and ease of use.
Instant and bread machine yeast is dried in a certain way to allow it to be mixed into flour without being proofed first. It is slightly more expensive than the old-fashioned technology. Regular, active dried yeast results in a slightly different flavor, which some people prefer. I have also found coarse, dried yeast in bulk at my health food store. The way it is manufactured, it takes about twice as long to reconstitute, but functions the same as powdered yeast once you proof it.
Cake yeast is compressed fresh yeast and is refrigerated. It has a shorter shelf life than the dried yeast, but I prefer its flavor in many German cakes. It is very expensive and hard to find in the US, so substitute dried yeast; one packet of active dry yeast (2 1/2 teaspoons) or instant yeast (2 teaspoons) for one cake (0.6 ounce in the US) and add a tablespoon or more liquid to the dough.
Generally, you can substitute one yeast for the other, although you may want to change the method of delivery. Instant yeast can be proofed if you like, but I do not recommend mixing active dry yeast or cake yeast with the flour directly as it does not dissolve evenly in a stiff dough.
- This page has an excellent discussion on yeast types used in baking.
- Also see Fleishmann's Yeast descriptions and
Red Star yeast products.
- Learn more about the science of bread dough.
Does salt hurt yeast?
Small amounts of salt can actually help yeast function better (0.5 - 1%), whereas 1.5-2.5% salt (by weight to flour) acts inhibitory. Salt is necessary for bread gluten structure, however, as well as for taste. Many breads are made satisfactorily with 2% salt.
Interestingly, sugar concentrations above 6% (by weight to flour) have a negative effect on yeast, as well. There is a special strain of yeast that works well in sweet and sourdough doughs.
What does kneading do to yeast?
Kneading does very little to yeast, since yeast should be evenly distributed after the first mixing. It does stretch and lengthen the gluten so that it can hold the nitrogen and carbon dioxide bubbles. The second knead is important, after the dough has risen once, to increase extensibility, even though it may not be a long kneading process.
Beating a dough hard does not hurt yeast either, you cannot break the cells that way. Professional bakers take care when mixing doughs so that the temperature does not exceed what is required by the recipe. Home bakers do not worry about that much because the small amounts of dough used at home do not require as much mixing.