Author Topic: Yeast Calculation  (Read 712 times)

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Offline LD

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Yeast Calculation
« on: December 02, 2011, 05:41:24 PM »
This sounds like a simple question in my head, but is probably more complicated then I believe.  If I want to change a dough formula to either speed or retard rise i.e. either change an emergency dough to a 24 hour fridge rise or vice versa, how would I go about figuring the change in percentage?  Using ADY yeast. 


Online Pete-zza

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Re: Yeast Calculation
« Reply #1 on: December 02, 2011, 06:49:55 PM »
This sounds like a simple question in my head, but is probably more complicated then I believe.  If I want to change a dough formula to either speed or retard rise i.e. either change an emergency dough to a 24 hour fridge rise or vice versa, how would I go about figuring the change in percentage?  Using ADY yeast. 


LD,

You are right. If you want to be precise, and in every instance, it is more complicated than you believe. The way to do it is discussed in Reply 6 at http://www.pizzamaking.com/forum/index.php/topic,5028.msg42572.html#msg42572. But even before doing the re-calculation of the amount of yeast (ADY), you would need a reference standard. An example, might be using a certain amount of yeast to achieve a certain desired dough condition (such as a doubling in volume) over a certain time period. Once you have those numbers, then you do the rest of the math to determine the amount of yeast to use for the new condition.

There is a pretty good online scientific calculator to do the various calculations at http://www.calculator-tab.com/.

Of course, you can also use a brute force approach where you experiment with different values. I don't know what kind of emergency dough formulation you have in mind, but generally emergency doughs use about double or triple the amount of yeast (ADY or IDY) than you might use for a 24-hour cold fermented dough. I'd have to see your particular dough formulation to comment further on the subject.

Peter

Offline scott123

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Re: Yeast Calculation
« Reply #2 on: December 02, 2011, 08:08:22 PM »
Peter, no offense to Red.November, but there's not a chance in heck that those calculations could reliably predict rate of fermentation for multiple temperature time periods.

It appears to be based on the assumption that yeast activity is linear- that, assuming the temperature stays the same, the yeast will be equally as active at the beginning of fermentation as at the end. They aren't. During longer ferments, enzymes play a larger role, generating sugar that may, to a point, hasten yeast activity, but also depending on how much sugar is generated, might slow it down.  Regardless of whether or not it's faster or slower, it is in no way linear.  And that's just one aspect impacting the way yeast activity might plot. It could be a J curve or even a hump- or maybe even a combination of the two.

There's probably some set of calculations out there that might take every single possible variable into account, and, along with a reference rate, could predict fermentation rate for various lengths of time/temp, but those calculations are not it.

LD, your 'simple' question is even more complicated that you even though it might be. The only reliable method for predicting yeast activity is through trial and error.  Control every variable (final dough temp, identical amount of kneading, same recipe- don't scale down or up, same bag of flour, same batch of yeast, same proofing temps, etc. etc.), use ballpark yeast amounts that you see in recipes to give you an approximate target and then carefully note the actual amount of time it took to double.  Once you dial in the yeast quantity for a given time, then you can start testing another length of fermentation, and, hopefully, because of the trial and error you've already put in, dialing in that length of time should be a bit easier.  Once you have two lengths of fermentation, then the third gets a bit easier, and after that, you can graph it.

This is for one single static recipe.  If you're the type that likes to tweak hydration or other ingredients, then that makes predicting fermentation a lot harder.  The best way that I've found is to begin with a popular fermentation of two days and a reliable recipe, use trial and error to reach the yeast quantity that achieves doubling in that time and then stick to that recipe for company. In other words, if your relatives show up and say "I want pizza now," tell them no. If you're planning a party, plan to make the dough two days in advance. You can experiment with longer and shorter time frames, but only do that when it doesn't matter if you're off.

I've made pizza hundreds of times, and, because of my incessant tweaking, I can make dough that's ready in exactly two days, but any shorter than that and it's a crap shoot. I've also been religious about documenting all my permutations of formulations, but I've been bad on going back to my notes and putting in when the dough had actually doubled so that hasn't helped.

If I opened a pizzeria, I could take my experience with yeast and my notes and have a protocol that would serve me, all year round, for yeast quantities and water temps, within maybe week or two, but it would be largely based on intuition, not on calculations.  Most pizzeria owners aren't fervent calculator users.

Oh, and this is for non sourdough doughs. If you really want to pull your hair out, add bacterial activity to the mix.
« Last Edit: December 02, 2011, 08:22:21 PM by scott123 »

Online Pete-zza

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Re: Yeast Calculation
« Reply #3 on: December 02, 2011, 08:54:42 PM »
scott123,

I don't know exactly what degree of certainty November had in mind in devising the method described in the post referenced earlier. I sensed that there were perhaps transitions in temperature that might not be embraced by his method and might affect the accuracy of the method, but beyond that I did not have any idea as to whether there were other possible disconnects. For example, if a dough in a cold refrigerator is brought out to room temperature, or vice versa, the dough will not instantaneously be at the new temperature. There will be a lag time. All I can tell you is that I have tried out November's method on several occasions--often out of curiosity--and the numbers seemed to work for me. The last time I used November's method was to help another member, Andre, as I described the process at Reply 36 at http://www.pizzamaking.com/forum/index.php/topic,13080.msg128439.html#msg128439. Andre later reported that he ended up reducing the amount of salt by 0.3% and he started the preferment 1 1/4 hours earlier than I suggested, but he apparently got very good results, judging from his post at Reply 48 at http://www.pizzamaking.com/forum/index.php/topic,13080.msg130280.html#msg130280. I tried to connect the dots as best I could but maybe there were other factors that played a role in the results Andre got.

Peter

Offline scott123

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Re: Yeast Calculation
« Reply #4 on: December 03, 2011, 05:09:22 PM »
Peter, if you look at November's calculations, I believe he factors in the slow process of cooling and warming, although, I'm not sure that he factors in the shape of the container, the material/insulating properties of the container or the fact that larger amounts of dough will take longer to reach the target temp than smaller amounts.

I read through the link that you posted, and I can't seem to find any mention of the reference rate dough.  Was the dough for Andre a conversion from an emergency single temp dough to an overnight multi-temp ferment?  Did your own experimentation involve an emergency conversion as well?  I might be able to see this formula being somewhat successful for a less meaningful time adjustment, like, say 4 days to 3 or 3 days to 2, because any error in the calculations won't show up that dramatically, but for an emergency to overnight, any error will be glaring evident because of the vastly disproportional difference in time- 3 hours is 1/8th the time of 24 hours, while 48 hours is 2/3 the time of 72.

Online Pete-zza

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Re: Yeast Calculation
« Reply #5 on: December 05, 2011, 10:40:18 AM »
scott123,

It took me a while but I found my notes on Andre's project to help refresh my memory on all of the calculations I performed.

As I noted in Reply 36 at http://www.pizzamaking.com/forum/index.php/topic,13080.msg128439.html#msg128439, I used November's method twice, once for the Preferment (poolish) and the second time for the final dough. For the Preferment (poolish), I used Didier Rosada's poolish numbers for a 12-15 hour prefermentation period (I settled on 14 hours) using 0.03% IDY (with respect to the weight of the poolish flour), a prefermentation temperature of 80-85 degrees F, and a poolish water temperature of 60 degrees. The reference rate for the poolish was based on 14 hours of prefermentation (from 8PM to 10AM the next day) at a prefermentation temperature of 82 degrees F (and a poolish water temperature of 60 degrees F). The predicted rate was based on a temperature of 64.4 degrees F. That resulted in IDY for the poolish of 0.071142%. I also had to decide how much poolish to use, as was also discussed in Reply 36 referenced above. And I gave instructions to Andre on water temperature and finished dough temperature to achieve better control over the overall process.

For the Final Mix, the reference rate was 18 hours of fermentation at a temperature of 80 degrees F, based on using 0.012% IDY. That set of numbers represented a doubling of the dough, and came from experiments I had conducted under similar circumstances. I described that scenario in the opening post in the thread at http://www.pizzamaking.com/forum/index.php/topic,7225.0.html. I wasn't sure how that set of numbers would work but it was the best I had to go on. The predicted rate was 6 hours at 64.4 degrees F and 4 hours at 80 degrees F. That calculation yielded a value of IDY for the final dough (Final Mix) of 0.032086%.

I later learned that Andre had about 20 people over to have pizza using the dough formulation that I came up with for him to use. Had I known that, I might not have even attempted to come up with a dough formulation :-D. However, when I looked at the final numbers, they looked right to me based on prior experience, and also as a gut check, which I have learned to value as highly as my calculations. I also wanted to have another test of November's method, for fun and to satisfy my curiosity. As I noted in Reply 36, everything was done on paper, not as a result of having tested the dough formulation I came up with for Andre. That made the exercise all the more interesting.

Peter

Offline scott123

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Re: Yeast Calculation
« Reply #6 on: December 06, 2011, 11:28:49 PM »
I'm not pointing any fingers, but I'm sort of amazed by how frequently people want to make major changes to their dough right before an important event.

As I look at your notes (thanks for taking the time to look those up), it seems that your adjustments, in the general scheme of things, were not overly dramatic, so it does seem to support my contention that the calculations might be appropriate for small-ish changes but not large ones.

This being said, if I was going from 82 degrees to 64 degrees on a preferment, I wouldn't have the faintest idea how much of an adjustment to make to the yeast, so if these calculations can actually consistently predict these types of changes, then I have to admit, they'd be useful.  Even if they only predict a half decent ballpark, that's better than nothing.

Online Pete-zza

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Re: Yeast Calculation
« Reply #7 on: December 07, 2011, 08:35:47 AM »
scott123,

Maybe Andre thought that I was a lot smarter than I really am :-D. He didn't say so, but maybe he had a Plan B just in case.

I don't think that there is much danger of people using November's method. You have to be kinda geeky to do that. I will continue to try November's method if the situation calls for it. The hardest part is getting an accurate reference rate. In Andre's case, it was fortuitous that I had one.

Peter

Online norma427

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Re: Yeast Calculation
« Reply #8 on: December 07, 2011, 09:18:48 AM »
Peter,

I donít know if you used Novemberís method to figure out the preferment Lehmann dough I use for market, but your method and formulation works well for my market pies.  :chef:

Norma
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Online Pete-zza

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Re: Yeast Calculation
« Reply #9 on: December 07, 2011, 09:51:59 AM »
I donít know if you used Novemberís method to figure out the preferment Lehmann dough I use for market, but your method and formulation works well for my market pies.  :chef:

Norma,

No, I did not use November's method that time. I used a more straighforward approach using the Didier Rosada information. However, had I thought of it at the time, maybe I could have used November's method. It wasn't until I came up with the dough formulation for Andre that it occurred to me that November's method could be used for a preferment. After all, a preferment is really a form of a dough.

Peter


 

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