The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

yeast and sugar

dlassiter's picture
dlassiter

yeast and sugar

In ALL my yeast breads, I add some sugar. Not a lot. Yeast fermentation is a metabolic process in which the yeast consumes sugar, turning it into ethanol and CO2. Certainly sugar helps to proof the yeast. But, I understand that you can make bread without any added sugar, and things work fine. In fact, it is said that sugar doesn't even actually help yeast bread rise. So I have to assume that flour itself provides enough sugar for the yeast to ferment. Is this correct? There sure isn't much sugar in flour. Maybe something like 01%.

pmccool's picture
pmccool

The flour contains enzymes--they were there in the original wheat kernels.  Some break down proteins, some break down starches.  Those that break down starches convert a small portion of the starches into sugars.  That's what the yeast consumes in doughs made with no added sugar.  A long, slow fermentation gives the enzymes more time to work, which yields more sugar.  Not only does this benefit the yeast, it also improves flavor and contributes to browning of the crust. 

Paul

kendalm's picture
kendalm

too much sugar inhibits yeast as most sweetbread / viennioise bakers know all too well. My son had a science project and we did a little experiment to prove - I cant remember the concentrations but at a point activity really halts as osmosis dehydrates the yeast cell - at the lowest level of breakdown the yeast is processing fructose and glucose - here's he details at 7th grade levels -

http://www.thefreshloaf.com/node/55354/too-much-sugar-starves-yeast-junior-high-sci-project-find-out

texasbakerdad's picture
texasbakerdad

"Yeast eats sugar, glucose to be specific. If there is no glucose around but there are other sugars, starches or alcohols, yeast creates machines (enzymes) to convert these into glucose."

https://www.thespruceeats.com/bread-making-yeast-faq-1447197

even more details below...

http://www.bakeinfo.co.nz/Facts/Bread-making/Bread-ingredients/Enzymes

dlassiter's picture
dlassiter

Very interesting. Thank you. I'm especially struck that yeast doesn't digest sucrose directly, but needs it to be made into glucose and fructose. Of course, that's what sucrose is. It's a combination of those two other saccharides. But it takes enzymatic activity to do the decomposition. That particular enzymatic activity works fast!

Now, the enzymatic activity in flour is striking. How long does that take to work? That is, when I add a bit of sucrose to my dough, BANG, the fermentation starts right away. If I didn't, would the dough sit and wait until the enzymes did their job on the starch? That is, if you want to make bread without added sugar, is it going to take a lot longer? I understand that longer fermentations develop more flavor. I just want to know if lack of added sugar *requires* longer fermentations.

texasbakerdad's picture
texasbakerdad

Let me be clear about something. Sugar-free bread is not some specialty bread. Sugar free bread is quite normal and is how bread is traditionally made.

Bread does not take a long time to rise when the recipe contains zero added sugars. And, the term "long" is relative. You can add more yeast to the recipe to decrease the rise time. Usually the sugar in bread recipes is added for flavor, the increased bread rise speed is a side effect. Not all of the added sugar ferments because the bread is cooked well before yeast has the opportunity to consume all of the available food. 

If i want a zero sugar loaf to rise in 4 hours, I might use 1/2 teaspoon of yeast. If I want it to rise in 30 minutes I would probably use 2 tablespoons of yeast. 

Ways to adjust rise times:

  • more or less yeast
  • hotter or colder dough
  • more or less added sugar
  • use a preferment
  • use flours that are easier for yeast to digest
  • The type of yeast can make a big difference (fresh yeast vs. bread machine yeast vs. instant yeast vs. active dry yeast)

hope that helps

dlassiter's picture
dlassiter

So if I'm in a hurry, added sugar is a help. If I'm not, it's not necessary. I'm not inquiring about "specialty bread". I make regular sandwich loaves every week. I'm not trying to prolong that job, and I don't add sugar for flavor. A tablespoon or two in a couple of loaves isn't going to change any flavor. So added sugar just makes things go faster.

texasbakerdad's picture
texasbakerdad

I googled "simple white bread recipe" and the link below was the first search result. The recipe I googled is very common because it is a relatively easy bread to make, you can make it in less than a day, and it is similar to sandwhich bread found in the store.

https://www.google.com/amp/amp.myrecipes.com/recipe/simple-white-bread

The recipe and the thousands of other white bread recipes like it share the same traits:

  • uses only all purpose flour or bread flour.
  • the whole process from mixing to baking takes less than 8 hours
  • commercial yeast is used
  • cooks around 350 dF

If you bake a bread with the characteristics above, you will notice the 2 tbs of sugar. Why, because that type of recipe produces a bread with very little natural flavor.

If however the bread uses some whole grains, uses a leaven, has an extended fermentation, or cooks at a high temperature (450 dF or more)... then the 2 tbs sugar might get lost amongst all the other flavors. 

Nothing wrong in my opinion with adding sugar or honey. I love my white bread, even though my wife tells me it is bad for me. My original comment was me trying to be clear that you can make fast rising breads with zero sugar and that doing so is not uncommon.

My apologies if I come across terse or have a 'know it all' written tone. I don't mean too. I think I have an unfriendly writing style.

dlassiter's picture
dlassiter

Thank you. I have the information I needed. I certainly don't need recipes, I make a dozen loaves every month, of both sandwich bread and others. My family loves my bread, but certainly not for the length of time it takes to make it. I add several flavorings - mostly dried spices, so sugar is not a real flavor enhancer. My standard recipe is done in four hours -- proofing to eating. Of course, a principal factor in keeping time short is warmth. In the winter, I just microwave the dough a bit to warm it up. Works well.

Georgenp's picture
Georgenp

"Ways to adjust rise times:

  • more or less yeast
  • hotter or colder dough
  • more or less added sugar
  • use a preferment
  • use flours that are easier for yeast to digest
  • The type of yeast can make a big difference (fresh yeast vs. bread machine yeast vs. instant yeast vs. active dry yeast)"

Thank you very much! This would help a lot.

Tyler Dean's picture
Tyler Dean

(I posted this on kendalm's thread about the science project with sugar and yeast, but I also wanted to post here because it seems more of an active conversation - hope it's okay to repeat myself for the sake of knowledge:)

I wonder if there would be a variation in results if different types of sugars were used. Something like sucanat, coconut/date or other types of palm sugars, maybe even invert syrup. Also, are any of you aware of the type of yeast which is more adapted to the higher levels of sugar?

https://www.wildyeastblog.com/osmotolerant-yeast/

On another note, how would this phenomenon differ with something like sourdough or yeast water? The types of yeast and organisms can be different as well as the Ph with homemade yeast cultures, so are these type of yeast affected by sugar in the same ways?

dlassiter's picture
dlassiter

I believe that most natural sugars are either glucose, fructose (monosaccharides) or sucrose (disaccharide). Yeast will eat all of them. Honey is about 70% fermentable sugars. I believe the one sugar that is not fermentable is lactose (milk sugar). As a result, it contributes sweetness that doesn't go away with fermenting.