The Fresh Loaf

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Why is yeast added when making a sourdough recipe?

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Marni's picture
Marni

Why is yeast added when making a sourdough recipe?

I know this sounds simple, but other than speeding up the rising, is there a reason to add yeast?  Or to look at it another way- why add the sourdough starter?  If the starter is not allowed to perform the rise, what's its purpose?  Does sourdough act as a tenderizer?  I'm asking because the sourdough oatmeal rolls I have making buy the dozens this week call for both but the sourdough taste is VERY mild and the recipe calls for 2t of yeast.  Trying to learn something new. Thanks.

Marni 

susanfnp's picture
susanfnp

Adding baker's yeast to a sourdough bread can be for the purpose of speeding up fermentation, or to tone down the sour flavor and allow more of the grain flavor to come through. The purpose of having sourdough at all in these breads is to produce a more complex flavor, to increase dough strength, to enhance the keeping quality of the bread, to achieve health benefits that come with sourdough (e.g., increased absorption of minerals), or all of the above.

Susanfnp

http://www.wildyeastblog.com

Mike Avery's picture
Mike Avery

Rye breads are a special case which I'll mention first.  To make a good rye, it really helps to acidify the rye flours.  Sourdough does this very, very well.  In Germany it has become common practice to use a very sour starter that is pretty well dead to acidify the rye flour and then to leaven the loaves with yeast.  This started sometime after the mid to late 1800's when commercial bakers yeast became available.  There is a growing trend in Germany away from this practice as it is seen as diminishing the flavor of the rye breads.

 

In wheat breads, people who suggest using commercial bakers yeast to start, or maintain, starters just don't understand what is going on.  A number of studues have shown that when a starter is healthy, it is so acidic that bakers yeast won't survive two feedings of the starter (call it a day).   Also, until the commercial bakers yeast dies off, it won't be a sourdough starter.

 

As to making breads, some French breads use levain and yeast.  A very, very small amount of yeast.  It is seen as a separate style in France.  In most breads, this isn't desireable.   If you add yeast, you are insuring that the starter doesn't have enough time to work it's "magic" to increase the acidity and flavor of the breads, to make micro-nutrients available.  When I see a recipe that calls for sourdough and commercial bakers yeast, I feel that the person who put the recipe together probably doesn't understand how sourdough works, doesn't have a good starter, or just doesn't trust their starter.  I omit the yeast and things work well.

 

You can adjust the flavor of the bread by varying the amount of starter you use and how long the bread is allowed to ferment.  In general, you should use a fresh starter.  I like to feed my starter, let it rise to a peak, and use it before it begins to decline.  Using less starter gives the starter more time to work and produces a more tangy bread.  Using more starter leads to a quicker rise and a less tangy taste.

 

Mike

 

susanfnp's picture
susanfnp

When I see a recipe that calls for sourdough and commercial bakers yeast, I feel that the person who put the recipe together probably doesn't understand how sourdough works, doesn't have a good starter, or just doesn't trust their starter. I omit the yeast and things work well.

One finds such recipes in Hamelman, Reinhart, Silverton, Leader, and Calvel, to name a few. I'm pretty sure all of them have robust starters and a pretty good handle on how sourdough works.

I'm glad that things work well for you when you omit the yeast. They work well for me, too, when I choose to omit the yeast. But it's disappointing that someone as knowledgeable as you, Mike, would promulgate the smug, misguided idea that the only reason for using yeast in combination with sourdough is that one is inexperienced or incompetent.

Susanfnp

http://www.wildyeastblog.com

SteveB's picture
SteveB

Mike,

With all due respect, you may want to rethink your statement: 

"When I see a recipe that calls for sourdough and commercial bakers yeast, I feel that the person who put the recipe together probably doesn't understand how sourdough works, doesn't have a good starter, or just doesn't trust their starter."

I don't think anyone would doubt that Prof. Calvel understood how sourdough works, yet he included a small amount of baker's yeast for consistent rising in his formulae for pain au levain (see his formulae in "The Taste of Bread" and "Bread & Baker: From the Source").  Personally, I don't use any, but I would hesitate to condemn those who do. 

ehanner's picture
ehanner

Susanfnp and SteveB,
I am surprised at both of your reactions to Mike's statement about the use of yeast with sourdough breads. I thought Mike made pretty good points and offered several reasons why authors would use yeast in "sourdough breads". I didn't see anything in his post that warrants your statement that he has a "smug, misguided idea that the only reason for using yeast in combination with sourdough is that one is inexperienced or incompetent." This statement is a total mischaracterization of Mikes post, Susan. He isn't condemning anyone, he is suggesting 3 reasons why an author would add additional yeast. Calvel uses a very small amount of bakers yeast for consistency in a commercial environment that operates on a schedule. He is in essence saying I don't trust my starter so I add bakers yeast to insure consistency. That is exactly what Mike was saying.

Susanfnp, in your first post you make the statement "The purpose of having sourdough at all in these breads is to produce a more complex flavor, to increase dough strength, to enhance the keeping quality of the bread, to achieve health benefits that come with sourdough (e.g., increased absorption of minerals), or all of the above."
The question was, why would a person add yeast to sourdough. The purpose of adding sourdough to a sourdough bread recipe is to use the leavening power of the  active sourdough culture to aerate the dough and flavor the bread. Using additional yeast changes the chemistry of the culture, alters the time required and perhaps the temperature needed for proofing and the taste of the bread. I suspect that the author's motives for adding additional yeast to a recipe have more to do with their desire to publish a recipe that will result in a successful bread. Keeping in mind the author hasn't a clue about the strength, activity or reliability of your starter.

Many if not all published authors of bread cookbooks have been telling us for years that a preheated stone is necessary to create hearth style artisan breads. It turns out that that general statement is also, ignorant. So let's not be attacking one of our own for pointing out the obvious.

Eric

susanfnp's picture
susanfnp

let's not be attacking one of our own

You're absolutely right that my response to Mike's post was unduly harsh. I apologize to Mike and all TFLers for letting my short fuse get the better of me. I (a person who sometimes uses yeast in combination with sourdough starter) did feel insulted by Mike's post, but that does not justify insulting Mike in return. Again, my apologies.

He isn't condemning anyone, he is suggesting 3 reasons why an author would add additional yeast.

You and I seem to have read Mike's remarks completely differently, Eric. I found nothing in Mike's post to imply that he felt that any of the reasons he suggests are actually valid ones. And in fact I would not say that any of the reasons he lists seem valid to me either. (But there are other reasons that he did not mention that I think are valid; see below) If one does not wish to condemn, starting a post with the title "Usually, ignorance" seems to me to be a rather odd way to communicate that.

The question was, why would a person add yeast to sourdough

The OP went on to say "Or to look at it another way- why add the sourdough starter? If the starter is not allowed to perform the rise, what's its purpose?" I felt my answer addressed that. I also thought that given the large amount of yeast she mentioned (2 t.) that this recipe probably was a case of a primarily yeast-leavened bread with the addition of some sourdough, rather than the other way around.

Calvel uses a very small amount of bakers yeast for consistency in a commercial environment that operates on a schedule. He is in essence saying I don't trust my starter so I add bakers yeast to insure consistency

My reading of Calvel is that he uses a small amount yeast (up to 0.2%) in some cases (and still feels entitled to call the resulting bread pain au levain) not for consistency, not because he does not trust his starter, but because the yeast, in small quantities, speeds up the second fermentation without noticeably affecting the taste of the bread (p. 92). This seems valid not only in a commercial envirnment that operates on a schedule, but also for a hobby baker who has a job, a family, and other interests and obligations to attend to.

Calvel also acknowledges a second style, the levain de pâte, which uses a larger quantity of yeast (his formula specifies 1%) in combintation with a natural starter. While not a true pain au levain, such bread seems quite acceptable to him. He notes the method "allows time savings at all the different stages of fermentation," produces "a noticeable loss in vinegar odor, allowing greater presence of the aromas derived from the flour itself" and "good keeping qualities" (presumably he means this in comparison to yeast-only breads). (p. 41)

So I hope that others will not follow Mike's lead in rushing to the conclusion that ignorance is the main reason why some sourdough recipes include yeast. Time savings -- is that not valid? A mitigation of sour flavor, with more flavor being derived from the wheat itself, while retaining some of the benefits of sourdough -- is that not valid?

If someone prefers to bake solely with sourdough, because they prefer the taste, the thrill of it, or whatever the reason, fine. I like to make and eat sourdough-only-leavened breads myself. I'm just baffled by why people feel it's necessary to think negative thoughts about the myriad competent, experienced, skillful bakers who sometimes consciously make other choices for very legitimate reasons.

Susanfnp

http://www.wildyeastblog.com

Janedo's picture
Janedo

This subject is very interesting. I just thought I'd add my own experience. As a Frenchy, I make several types of baguettes. I've tried pure sourdough baguettes and I've done ones on poolish with yeast, but in this family the very BEST ones are a nicely hydrated dough with some sourdough starter and a bit of yeast. The bread is left to rise 2-3 hrs instead of longer for regular sourdough, then another hour or so. The sourdough gives a perfect, just chewy enough texture, but not too much. It also gives just enough flavour but not sour. And the yeast gives a quicker, airier rise.

I agree with Susanfnp, the sourdough even if it doesn't have the time to FULLY develop it still adds great texture and taste and bread made with it keeps longer. So, there are definite advantages to mixing.

 

Marni's picture
Marni

I am finding all of this so interesting.  So, if you all don't mind considering another question... The recipe I referred to above also calls for a bit of baking soda.  Does that also temper the sourness?  Is there another reason for it?

 Also I just finished baking the sourdough banana bread from this site.  (It smells incredible!) It is a quick bread and clearly risen by the soda and baking powder.  I haven't tasted it yet, so I wonder again since the sterter has no time at all to effect the wheat proteins, what's its purpose?  (other than using some up so I don't have to waste it, for which I am grateful)

Marni

Richard L Walker's picture
Richard L Walker

James Beard used the argument of consistently reproducible results as his reason to use yeast with the sourdough  It was the inconsistent nature of sourdough that kept him from being a true fan.  Had he lived today he might have given it another look-see.  A lot more is known about it than when he was around ... even though it wasn't that long ago.

The more variables you can control ... the better and more consistent the results. 

Janedo's picture
Janedo

Without being able to explain why, from experience the sourdough changes the texture and amount of rise in quickbreads, muffins and pancakes. But the best thing to do is try and compare. Take a regular recipe that calls for baking powder and baking soda, drop the powder, add a half a cup of starter and keep 1 tsp baking powder, then compare the two recipes. Personally I think sourdough is great in quickbread! And even if it doesn't have time to develop the sourdough is there and it's healthy!

bwraith's picture
bwraith

One significant difference between instant yeast and a sourdough starter is that instant yeast is basically just the organisms with very little other contribution. However, with sourdough, you have to contribute the fermentation byproducts in the starter or sponge to the dough in the next stage along with the organisms.

In the case of sourdough, unlike instant yeast, there is not a way to isolate the organisms themselves and inject them separately into the final dough without including the fermentation byproducts that were produced while the starter or sponge matured.

So, the fact that putting a large amount of instant yeast into a dough and raising it quickly results in less flavor, while a small amount of yeast over a longer period of time results in more flavor, does not carry over well to sourdough methods.

In the case of sourdough, a small starter or a large one will result in about the same amount of fermentation byproducts in the final dough simply because the accumulation of fermentation byproducts occurs all along in both the starter or sponge and the dough. It may be possible to accumulate an excess of fermentation byproducts relative to the organism count by allowing an earlier step to mature additionally, similar to the use of preferments with instant yeast, but it will affect the texture and ability of the dough to rise in the later stages. Instant yeast can be a useful tool to compensate for those effects.

One of the reasons using a small amount of starter for a longer rise results in a satisfying flavor and texture in the case of sourdough - different from instant yeast which needs the long rise to accumulate fermentation byproducts - is the effect of the longer soak the flour experiences in that case. Very similar results can be obtained from a large sponge and an autolyse with a shorter rise time for the final dough with sourdough. In other words, it is possible to get similar results from two-step methods with a large preferment and one-step methods with a small starter with sourdough. It is also possible to get very different results by increasing the ripeness of the preferments in the two-step method. It is further possible to add instant yeast to change the final flavor and texture in either case.

There are good reasons to use both instant yeast and sourdough in combination, which take advantage of the difference between instant yeast and sourdough in their respective effects on flavor, texture, and gas production rates.

Bill

nbicomputers's picture
nbicomputers

a while back some one that asked if he could exchange a clear flour for a hy gluten flour for a jewish rye bread he asked about a name brand flour that cannot be bought in a store and named the other flour he wanted to exchange it for that also could not be bought in a store.  well since he knew about comerical flours i told him no and explained that the flours he asked about came from two diferent families. i gave him some tech data about the flours as well.

Well to make a long story short I GOT REAMED a new one by the board mod for that one.  compairing that to this my answer was tame.

i hope that fair play will prevail and another reaming will be comming soon.

duck!!!!