The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Minimum amount of yeast

  • Pin It
kolobezka's picture
kolobezka

Minimum amount of yeast

Hi!


I would like to ask what is the minimum amount of yeast (commercial) to use in a recipe that would not negatively affect the results.


I have read that yeast can reproduce but in fact it has not enough time to do so during dough fermentation. It just eats (and therefore produces gaz and increase volume, I guess).


Of course lean dough needs less than fat- and/or sugar-rich dough. And less yeast needs more fermentation time. Are there other factors that should be taken into consideration (whole wheat, rye, multigrain...)? And is there a general rule of thumb what would the minimum for different types of bread be? The avarage seems to be 10g fresh yeast (1tsp instant) for 500-600g flour. Can this be reduced?


For example I do not understand why in ABED by Peter Reinhart there are 4g instant yeast for 560-680g flour in one case (eg p. 72/73 - 50% and 100% Whole Grain Rustic Bread) and then 10-15g instant yeast for app the same quantity of flour in other breads (eg p. 83 Every Day 100% WW Sandwich, p. 102 Many-Seed, p. 113 Wild Rice and Onion), when there is not a difference between fat and sugar content. Would it be possible to reduce the yeast amount in all recipes?


Thanks for help


zdenka

Mini Oven's picture
Mini Oven

And even instant yeast is only one form of a variety of yeast.  If you are aware that there is wild yeast in the flour also, I guess the minimum amount would be "none."  There are recipes where no yeast is added and the flour ferments with the liquid that has been added to it.   The problem that may arrise is: will the dough strength hold up long enough for all the yeast replication that is needed to raise the dough using yeast?


The reason different recipes call for different amounts of instant yeast even with the same amount of flour, is to vary and control the fermenting process. That is what flavor is all about.


Yeast reproduce by budding and they double their population every hour to 2 hours under ideal conditions.  Yeast can also run out of available food and they produce products that when a saturation level is reached, slow down or stop the yeast from budding.


Lets back up a little bit.  It might help to think of the whole dough and fermentation as a negative process with positive results.  From the time ripe grain or flour gets wet it purpose is to feed a new plant as it degenerates and falls apart eventually back to basic elements.  Fermentation is in reality the breaking down of the flour.  It goes thru different stages of decomposition and we take advantage of this process trying to control it and  make usable food.  


There are also enzymes in the flour (some are added to instant yeast) that also react as well.  Various gluten levels can lengthen dough strength.  Factors vary from flour to flour and in different quantities and these even vary from season to season, year to year.  All have influence on the fermenting process and our ability to trap the by-products of fermentation, gas, acid, aromas, etc. to make bread.  It is a balancing act.  


It is also important not to let the process advance too far too fast out of our control.  We control the factors: moisture, temperature, yeast and each ingredient and expect certain results.  All the factors have parameters of too much or not enough with losses or gains that affect other factors both positively and negatively.  The mind boggles!  A good recipe has these factors all in consideration and by following it, you should come out with decent bread. Many are pretty flexible and so "tweaking" a recipe with small changes is easily done.


I like to reduce the yeast when I want a longer fermenting time than the recipe.  I start by reducing in half first and seeing what happens, then add more or less.  If the recipe doesn't have a total wet time of at least 6 hours, I reduce the yeast.  That is my rule of thumb.


Mini


 

Yerffej's picture
Yerffej

Zdenka,


I saw your post and was going to answer but Mini just covered the subject so superbly that there is but little left to be said.


Jeff

AndyM's picture
AndyM

I would add just a couple of things:


1) Whole grain flours (all other things being equal) generally have a higher activity level than refined (or white) flours.  My understanding is that this is because they have a higher level of enzymatic activity.  More enzymatic activity means more yeast food is produced, and if more yeast food is produced, more yeast can be fed in the same amount of time.  So some bakers will add more yeast to doughs with more whole grain flours.


2) The doughs that you mention with more yeast all have ingredients that lower the relative percentage of gluten (compared with the dough with less yeast).  An all-whole grain dough will have slightly less gluten than a 50/50 dough, and the gluten that is developed will be lower quality.  The addition of seeds or rice and onions will also interfere with optimal gluten development, and lower the relative proportion of gluten in the final dough.  Some bakers will want to compensate for the lower gluten proportion (and lower gluten quality) by adding additional yeast - the theory is that more yeast organisms will produce more gas at any one time, and if the poorer quality gluten does not hold as much gas inside the loaf, then producing gas at a faster rate means that more gas will be inside the loaf at any one time.  However, as Mini points out, this goal of producing more gas must be balanced with other desirable characteristics of bread, such as flavor development, which occurs best with longer fermentation times.  So with every step toward faster gas production, there is a corresponding step away from optimal flavor production.  Where each baker decides to be on that continuum is a very individual decision.


For a direct answer to your direct question, Zdenka, yes, you can reduce the yeast in just about any recipe.  The results of any reduction of yeast in isolation would be expected to be as follows:


a) increased bulk fermentation time.


b) increased final proofing time.


c) increased production of flavor compounds through fermentation - this will likely yield more complex flavors including more of the characteristics of sourdough creeping in, and less of the "yeasty" taste.


d) increased risk of failure - as Mini notes, a dough does have a life-span within which it will hold up its strength.  If fermentation time goes beyond this life-span, the dough will start to fall apart.  My understanding is that this is mostly due to the activity of protease enzymes, which attack and degrade gluten.  As with other enzymes, proteases are more active in whole-grain flours, so this risk is likely magnified in whole-grain doughs.  Also, because final proofing times will be increased, there is an increased risk of minor forming errors causing loaves to deflate.  Loaves that are not formed with adequate surface tension will have an increased risk of flattening out before they go in the oven, and not holding their oven spring very well.


So there are benefits to cutting down on the yeast, but also risks.  Personally, I try to use the least possible yeast and accept the risks.  I usually use about 1/8 tsp of active dry yeast in a batch of about 950 g of flour.  If using sourdough, I'll use about 10% pre-fermented flour (or about 150 g of stiff starter).  First fermentation is long (about 12-18 hours, depending on the room temperature), and final proofing is usually about 2 hours.  And yes, I fail sometimes, and end up with pancakes.  The pancakes still taste really good, though, and since it's just me eating the bread, and I don't have to take any embarrassing pictures if I don't want to, I can easily accept that risk.


Best of luck, and if you do any experiments, I'll look forward to some pictures of your results.


Andy

kolobezka's picture
kolobezka

Thank you very much Anydy for such a great and detailed explanation and some concrete hints! It helps.


Actually even for 100% WW Peter Reinhart uses 0.6% instant yeast in one case and 1.2% in another.


I have used 2% fresh yeast for most breads but thanks to your encouragment I will try less. I may not go down to app 0.2% (which would roughly be the equivalent in fresh) as you, but 0,5-1% is certainly wort trying.


Thank you very much!


zdenka

kolobezka's picture
kolobezka

Thank you very much - Mini and Jeff. It gives me a better understanding.


May I add two more "yeast" questions?


 


- is it correct to say that using more commercial yeast is less healthy? Of course wild yeast is always better but this is a different issue (and my new  - second starter is almost ready :-)) But as for commercial yeast - Saccharomyces cerevisiae - if you use less of it in a recipe, it will increase during the longer fermentation anyway... or not?


 


- what happens when commercial and wild yeast are in the dough together? I have read that the commercial yeast would not survive the acidity created by thee sourdough.


But why then is it recommended to use a small amount of commercial yeast with a starter when reducing fermentation time is desired? Does it have any effect?


Or adding a sourdough starter into a yeasted bread to enhance flavour? How does yeast manage to accomplish its work in such an environment?  (I have done this many times and it does not seem to be harmful, but I do not understand the theory then).


Thank you!


zdenka

diah's picture
diah

Yeah me too would like to know which yeast is healthier to use. Commercial yeast of wild yeast. And do anyone know usually those bakers use which yeast for their bread. I have never bake using wild yeast. Would like to use wild yeast but it seems that it takes days to be able to use wild yeast. I will one day make my own sourdough starter if I have the time. 

mlucas's picture
mlucas

As to the health-related effects of baking with wild yeast (aka sourdough) or using longer fermentation times with regular yeast, see this 2007 thread: Healthy Sourdough


FreshLoaf user Andy (is that the same person as AndyM in this thread?) does a really good job of explaining things. In summary:



  • additional fermentation does a better job of releasing enzymes and pre-digesting the dough so that the humans can process more of the nutrients from the bread

  • sourdough contains more variety of organisms which do a better job of the above, but commercial-yeasted preferments still help

  • there may be benefits to the fact that some of the lactic acid bacteria in sourdough are actually the same species as some healthy intestinal flora in humans (so-called probiotics). However this is hard to say for sure because the organisms are killed in the oven, so it would only be true if something they did to the dough, made it more beneficial to those organisms once the bread makes it to your intestines.


@zdenka, regarding using commercial yeast and sourdough together: In Whole Grain Breads Peter Reinhart includes a lot of hybrid recipes that use both a sourdough preferment and commerical yeast. The commercial yeast is added at the end to speed up the final bulk ferment & proof*. So you can definitely use both in the same recipe, I think it's a matter of understanding what they're doing.


*he says he needs to speed it up because of how he uses whole-grain soakers, and once the soaker is combined with the preferment the dough can break down quickly due to the high amount of enzymes in the soaker.


I think it may be true that over a longer period of time, the acid in sourdough may kill of the commercial yeast, I've heard that before too.


Mike

kolobezka's picture
kolobezka

Thank you Mike for explanation and the link. It helped me a lot.


So, according to PR it is not recommended to use a soaker in a pure sourdough - am I right? Well I have not tried the soaker method with pure sourdough yet, but with cold 24hour fermentation with commercial yeast there did not seem to be any problem. Even if the flours in my country are generally very weak.


Do you have any experience?


zdenka

AndyM's picture
AndyM

Hi Mike-


That's a different Andy, and one who knows a lot more about human digestive physiology than I do.  What he says about dough chemistry and fermentation sounds quite solid, and I have heard anecdotal reports of good digestive results being associated with more completely fermented doughs.


Andy (the other one)

Mini Oven's picture
Mini Oven


Saccharomyces cerevisiae - if you use less of it in a recipe, it will increase during the longer fermentation anyway... or not?



Yes it will increase.



is it correct to say that using more commercial yeast is less healthy?



No it is not correct to blankly say that.  There is much discussion and debate, not only about the yeast itself (allergy or intollerance) but about the short fermenting times that can be achieved by using it.  Wild yeast have a symbiosis with bacteria found living with wild yeasts cultures.  So one cannot compare them without including a debate whether these bacteria make a bread more healthy.


It is possible to use commercial yeast and prolong the fermenting time.  Seems to go against trends and be a healthy option.  Truly more studies need to be done.  And the question... less healthy than what?  Using more than the recipe stipulates?  Yeast gives a kick to the fermenting process; speeds it along.  There are some who eat denatured yeast regularly as a supplement.  Commercial yeast also has a more neutral flavor and can easily be used in sweetened or unsweetened doughs.  It certainly has its place as a tool.  A speedy wild yeast could also present debate with fermenting times.



what happens when commercial and wild yeast are in the dough together? I have read that the commercial yeast would not survive the acidity created by the sourdough.



When they are thrown together, how much of each?  Ok, the commercial yeast goes after its food, the wild one too.  The commercial yeast is fast to produce gas to raise the dough, you have to decide to bake it when it's ready or risk loosing total dough structure.  The wild yeast did not have the chance to work with their bacteria, they need more time to raise the acid levels too.  So I ask you, did the commercial yeast bow to the sourdough?  Hardly.   At most the wild starter added a little flavor. Now one could make the dough with the sourdough first, and later add the commercial yeast for a fast final lift.  This is often the case to guarantee rise in very sour doughs or to make a less sour sourdough cutting the long fermentation short.  If the sourdough would kill the commercial yeast on contact, then there would be no reason to use commercial yeast in this way.


However; if you are maintaining a starter and both are together, eventually the rising acid levels and long feeding cycles make it harder for the commercial yeast to survive, it will eventually be overpowered by sheer numbers of the wild yeast (could be more than one type) and their acid producing groopie bacteria.   The acid at high concentrations will slow all the yeasts from budding and I suspect a little more complicated than just that but the commercial ones are less flexible when it comes to survival.   This could take weeks but the wild ones will come thru.

AndyM's picture
AndyM

...on their heads. 


Sourdoughs contain several different strains of yeasts; the most prevalent group is called saccharomyces exiguus.  This type of yeast happens to prefer a more acidic environment, so it is particularly well-suited to being in a sourdough starter, which is usually kept fairly acidic.  Even within a starter culture, though, acidity varies.  When you first build up a starter, you add in lots of new flour and water.  This brings the pH up closer to neutral, then as the culture ferments the new flour, the starter's pH gradually becomes more and more acidic.  This also happens when a starter is added to a dough - adding all that new flour and water (and salt and any other ingredients) leads to an environment that is less acidic than the starter was before it was added to the dough.  So, if you add some baker's yeast at this stage, the pH is likely to be well within the baker's yeast's comfort zone.  It will do quite well.  As the dough ferments, it will become progressively more acidic, and eventually the pH will go so low that the baker's yeast (sacc. cerevisiae) will have less and less activity.  The yeast in the sourdough culture, though, being mostly sacc. exiguus, will do very well at these more acidic pH levels, so the dough will continue to have acitivity even after the fermentation of the sacc. cerevasiae has decreased.


On the pH scale, the numbers we are talking about are roughly: commercial yeast (sacc. cerevisiae) usually prefers a pH of about 5-6.  This is slightly acidic.  Commercial yeast fails to thrive at a pH below about 4.5.  Sourdough starters, when they are ripe, usually measure about 3.5-4.5, which is outside of the comfort zone of commercial yeast.  But it is perfect for sacc. exiguus strains.  So ultimately, each yeast strain has its comfort zone, and pH is one factor that determines the activity level of each strain.  And in the lifespan of any one dough, it is certainly possible to pass through the pH levels that enhance the activity of each strain, starting with a less acid dough that favors commercial yeast, and leading to greater acidity that brings on the activity of Sacc. Exiguus. 


In practice, my experience has been that commercial yeast operates so quickly that a "mixed" fermentation dough can move too fast for the sourdough to be able to contribute too much.  I've had breads that contained sourdough starter, but ended up with essentially the flavor of commercial yeast fermentation.  So I would tend to go very light on the sacc. cerevisiae and more heavy on the starter content to achieve a better balance.  But that is just my preference showing through (and confidentially, I rarely use commercial yeast at all anymore, as I almost always prefer the flavor profile of sourdough breads).


Hope this helps, and many thanks to Mini for her insights,


Andy

Yerffej's picture
Yerffej

Zdenka,


While I would not call commercially yeasted bread "unhealthy", I do eat sourdough bread almost exclusively because of health.  A little yeasted bread can make for an uncomfortably full stomach whereas a lot of sourdough does not have that effect.


When comparing yeast vs. sourdough I would say that sourdough is a much healthier choice but that does not make yeast un-healthy...although I do have my doubts about the health aspects of yeasted bread.


Sourdough is essentially a fermented food and like yogurt or sauerkraut, and these are foods that are very good for the body,


Jeff

Mini Oven's picture
Mini Oven

The kids BBQed yesterday and they had planned the whole meal including a purchased baguette and smeared it with garlic butter.  They ate lots of salad with their meat and grilled zuchinni and peppers.  What got left over?  The bread.  Smart kids.  I thought there was enough raw vegies in the salad for twice as many people.   That was a low carb meal.


Mini