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Interesting Sweet Stiff Levain pH data

Benito's picture
Benito

Interesting Sweet Stiff Levain pH data

If you read my blog here you may have noticed my use of sweet stiff levains (sugar added to the levain) for my enriched doughs in particular the Hokkaido milk bread.  I had never bothered to measure pH of the dough or levains that I’ve made for this type of bread but decided I should check it today.  

I’ve read, correctly or not, that using a sweet levain may encourage yeast growth over LAB.  I’m not sure if that is correct of not but that is what I have read.  Not being a microbiologist with access to a lab the one thing I can do with my baking gear is to measure pH and rise.

In theory, I think that if there is significant growth during fermentation of the levain that must indicate yeast population growth.  Yes I am aware that LAB also produce some gas, but the yeast are the major producers of gas during fermentation and LAB are secondary.  LAB on the other hand are the primary producers of acids during fermentation potentially producing both acetic and lactic acids.  

So getting to the point I made a sweet stiff levain last night at this ratio 1:1.33:2.9:1  starter:water:flour:brown sugar.  The pH immediately after mixing was 5.16.  This morning after it had about a 3-3.5 x rise the pH was 5.00.  I was quite surprised at the minimal fall in pH given the typical rise.  This leads me to believe that the addition of sugar to the stiff levain does apply more negative pressure on the LAB than it does on the yeast given the excellent rise (gas production) and minimal pH drop (acid production).

In contrast I made a stiff levain without sugar using the same flour as the sweet levain, at the same time it had a pH of 5.37 after mixing and in the morning with a 3.5x rise it had a pH of 4.05 also typical for my stiff levains at peak when I use them.

Obviously I am unable to measure total titratable acid (TTA) as that would be the most accurate measure of the actual acid production.  But given the huge difference it the delta pH drop I believe I can say that the addition of sugar does “seem” to encourage yeast reproduction over the LAB.

What do you think?  Can you explain the difference in the delta pH of the two levains in another way?

Benny

Abe's picture
Abe

After my initial read through your comment, Benny, my first thought is what is meant by a "sweet" starter? A sweet stiff starter doesn't necessarily mean sweet but rather through a special maintenance the tang is kept at bay. This might be a 1:1 feeding over a day at 3 hourly intervals. That's a bit different than simply adding sugar to a regular starter feed. 

So I guess what i'm trying to say is a "sweet" stiff starter, like a pasta madre, is not necessarily sweet but rather a lack of tang allowing the yeast flavour to be more dominant. I think this is another crossover when it comes to terminology. 

Benito's picture
Benito

Good point, I’ve added to the first sentence what I mean by sweet levain.  I can understand that some bakers might think something different when reading that term. Thanks Abe.

greyspoke's picture
greyspoke

Interesting.  I have found that stiff levains really help with being able to push the final fermentation farther without the dough over-fermenting, though with a more acetic tang to the final loaf.

I have been experimenting with salty levains (~6% by weight of the water content) with some success.  I can ferment for longer after a 100% hydration levain and get a better (for me) flavour.  But I am only really scratching the surface I think, so many other variables to consider.

So now I can try sugar instead/as well!

Possibly the same  sort of thing going on, yeasts being more tolerant of dissolved stuff?

 

 

Debra Wink's picture
Debra Wink

Thank you Benny, that really shows a clear difference, doesn't it? I'm curious to know why you went with brown sugar (which is acidic) instead of white --- does it fit better with the flavor profile of the bread you are making?

dw

Benito's picture
Benito

I thought that the additional flavour of the brown sugar would add something to the flavour of the bread.  I also find that the brown sugar dissolves more easily when making a stiff starter.  I only realized that it was more acidic last night when I made the two starters and noticed the significant difference in the pH.  Thanks for reading Debra.  Do agree with my findings/assumptions?

Benny

Debra Wink's picture
Debra Wink

I’ve read, correctly or not, that using a sweet levain may encourage yeast growth over LAB.

This leads me to believe that the addition of sugar to the stiff levain does apply more negative pressure on the LAB than it does on the yeast.

It's the second one. LAB have higher minimum water requirements, and the sugar pulls water away. Yeast are just better at dealing with that. Yeast do love sugar, but I'm not sure at what level the sugar becomes more inhibitory in dough than promoting.

My quick calculation shows you're at approximately 100% flour, 45% water, 35% sugar and 35% starter. Is that right? Clearly you haven't exceeded what your yeast (or gluten) can tolerate given that the rise in that one was nearly as high as the other.

Thank you for sharing this :)
dw

Benito's picture
Benito

Debra thanks for your input and confirming what I thought to be the findings of this.  It is always nice when one’s experience confirms what is known about the microbiology.  Yes your calculations are correct.  I’m still a bit shocked at how little the pH moved in the sweet starter.  Had I not tested the pH myself I would never have believed it.  I have another sweet starter going tonight and the starting pH is almost the same 5.15 this time.  I’ll update this post with the morning pH at peak again. Again, thanks for sharing your knowledge with us, it is always appreciated.

Benny

happycat's picture
happycat

I'm not totally following all this, but given "brown sugar" is white sugar with molasses added, you could presumably tweak ph further by just using molasses (or making your own molasses-sugar combo) 

Benito's picture
Benito

This is true but since I have brown sugar, why not use it 😉

DanAyo's picture
DanAyo

Benny, I’m curious.
Why so elaborate? Is there a reason?
” So getting to the point I made a sweet stiff levain last night at this ratio 1:1.33:2.9:1  starter:water:flour:brown sugar. ”

Why not 1:1.5:3:1?

I know you must have a reason, but my curiosity is piqued.

BTW - interesting experiment!

Benito's picture
Benito

Dan, when written out the looks elaborate, but in fact the actual measurements are even and easy to measure.  I looked at the ratio of sugar to starter in other bakers’ sweet starters and then adjusted the water and flour so that the levain would be ready in the morning after an overnight fermentation.  In fact you’re right, I could even out the ratio and make it look less daunting, but what I’m doing is working so I just haven’t bothered.  I wish I had a more interesting reason for you!

Benny

Abe's picture
Abe

Could it be that yeasts are more efficient than lactic acid bacteria in metabolizing sucrose? 

Benito's picture
Benito

I have no idea, but Debra has responded above Abe.

Benny

Benito's picture
Benito

I made another sweet (sugar added) levain at the same ratio mentioned above last night for another milk bread.  The results are reproducible, which is always a good thing in science.  The pH of the levain at mix was 5.15 and 11 hours later with a 3.5-4x rise the pH was only 4.98.  So this time a 0.17 drop in pH.

 

DanAyo's picture
DanAyo

Didn’t want to hijack your interesting post, so the experimental data is published to my BLOG.

Thanks for starting such an interesting experiment.

Danny

BTW - are you using whole rye for feed?

 

Benito's picture
Benito

I’m using these starters in my 100% whole wheat Hokkaido sourdough milk breads so the levains are 100% whole wheat but as you know my starter is 100% rye.

I’ll be interested in your findings as well.

Benny

JonJ's picture
JonJ

This suggests a practical application of potentially being able to ferment further, to a higher volume increase, before acidification commences. Interesting to see how this can be used.

I did wonder if it might be specific to the types of bacteria that are in your specific starter. Perhaps the species that you have are simply not osmotolerant, but maybe others are. It will be interesting to see what Dan comes up with.

Also, with sugars we have a whole palette to work with - refined, muscovado, demerara, coconut.... Wonder if this is something we can also use to get a different desired outcome.

Benito's picture
Benito

You’re right Jon it could be another tool we could use. 

tttt1010's picture
tttt1010

Just want to say, this question has been on my mind for the past few months, so thanks for getting some data on this.

Benito's picture
Benito

You’re welcome it’s great to have confirmation of this. 

Abe's picture
Abe

I remember seeing a question asked which went something like this...

Why put a small amount of yeast in a dough when you can put in a large amount and make the bread quicker?

Answer went something along the lines of: Because there's more happening inside a dough than just yeast eating sugar. 

For yeast to metabolize sugar in the flour the flour has to go through a change. This happens when it mixes with water, enzymes get to work breaking down the complex carbohydrates into simple sugars for the yeast to feed on. Just throwing in a lot of yeast to get a quick bread doesn't result in a better result. 

I wonder how this translates into adding sucrose into a starter. The yeast have more readily available food and don't need to hang around for the enzymes to do their job in breaking down the flour. The starter, or dough, will leaven with less of the breaking down of the flour needing to take place. The flour itself is less consumed with the yeast just reacting more so to the sucrose.   

In other words instead of "...because there's more happening inside a dough than just yeast eating sugar" it's now more "...because there's less happening inside a dough and more of yeast just eating sugar". 

The food source has been altered and therefore results will do so to. 

Also, if it's simply a case of low hydration affecting the yeasts and Lab differently you'll need to also think about how the sugar is added. Sugar can either be a wet or dry ingredient affecting the dough differently depending on how it's added. This would also mean the sugar is not really integral to the experiment if this is the only reason. 

Benito's picture
Benito

Excellent points as always Abe.  I didn’t start out to make this an experiment, I just had two similar levains going at the same time so thought it would be interesting to compare their pH at mix and at peak.  I was surprised at how different they were.  The idea behind making the sweet stiff levain was partly to try to enrich the yeast component since the dough the levain would have to raise was going to be an enriched dough which is known to be more difficult to leaven.  Also, the additional flavour from the brown sugar in this instance was a positive to boot.

Our Crumb's picture
Our Crumb

Benny,

If the net result (objective?) in your exercise is to tip a levain's yeast/LAB balance to the former, it might be interesting, along with including sugar, to use RYW as its "water", as I reported last Spring.

Tom

Benito's picture
Benito

Yes Tom, I still remember your post and I haven’t forgotten about wanting to try yeast water again.  I wonder if my original grape yeast water supernatent will still work to inoculate a new yeast water.  I believe it should.  At some point I will get back to doing some work with yeast water.

DanAyo's picture
DanAyo

SeeTHIS LINK .

The starter with sugar tasted excellent. Almost like cookie dough :)
But it didn’t rise as strongly as the other two.

Benito's picture
Benito

Just another data point from today's levain.  I made an overnight stiff sweet levain for a 100% whole spelt loaf I'm working on today.  The levain was 16 g starter 25 g water 47 g whole spelt and 16 g white sugar for a 1 : 1.3 : 2.9 : 1 ratio or more importantly 1: 1.3 sugar to water by weight.

The pH after mixing was 5.2 and the next morning after 10 hours of fermentation the levain had risen 3.5 times and the pH only dropped to 4.86.  Typically I aim for a pH drop of 1-1.3 for the levain before I use it when it isn't a sweet (sugar added) levain.

By using this type of levain I'm hoping that the pH will fall more slowly as the 100% whole spelt dough rises.  This might maximize the lift while reducing the rate of gluten degradation in a flour that is gluten poor.