Author Topic: Fermentation Curve  (Read 3399 times)

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Offline 2stone

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Fermentation Curve
« on: November 09, 2012, 07:31:04 AM »
I have been intrigued over the "Fermentation Curve" more specifically where the sweet spots are.
Where in the fermentation curve do you give it a fold /punch down / or degas.
As shown here http://www.bioc.rice.edu/bios576/nih_bioreactor/NDL_Bioreactor%20Page.htm (attached pic)
Would you degas in the "Stationary Phase", and if so would the degassing result in a back-step to the "Log Phase".
Would you degas in the log phase, and where would that put it? or should all this activity be done in the "Stationary Phase"?
Does this whole curve repeat itself every time you degas (to simplify it, do you have a new mini fermentation curve each time you degas or fold?
Lastly would it be correct to assume that the sweet spot is towards the end of the "Stationary Phase"

The link to the curve again: http://www.bioc.rice.edu/bios576/nih_bioreactor/NDL_Bioreactor%20Page.htm

regards
willard
« Last Edit: November 09, 2012, 07:40:42 AM by 2stone »
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Online TXCraig1

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Re: Fermentation Curve
« Reply #1 on: November 09, 2012, 11:22:34 AM »
I have been intrigued over the "Fermentation Curve" more specifically where the sweet spots are.
Where in the fermentation curve do you give it a fold /punch down / or degas.
As shown here http://www.bioc.rice.edu/bios576/nih_bioreactor/NDL_Bioreactor%20Page.htm (attached pic)


This is an interesting question I hadnít thought about before.  One minor thing to note, you have shown a growth curve which is closely related to fermentation in the case of bakerís yeast (S. cerevisiae), but to call it a ďfermentation curveĒ is technically not correct. Fermentation, in the case of yeast in pizza dough, is the process of extracting energy from carbohydrates needed for growth and reproduction.

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Would you degas in the "Stationary Phase", and if so would the degassing result in a back-step to the "Log Phase". Would you degas in the log phase, and where would that put it? or should all this activity be done in the "Stationary Phase"? Does this whole curve repeat itself every time you degas (to simplify it, do you have a new mini fermentation curve each time you degas or fold?


The growth phases are based on food supply and type (other than lag which is the yeast acclimatizing to the new environment). You canít step back from stationary to log without adding a new supply of food. There is a deceleration phase at the end of the log phase. Manipulating the dough at this point might appear to be back stepping from stationary to log by moving yeast away from their waste products and to new food, but it would be short lived Ė effectively shortening the deceleration phase rather than back stepping from stationary to the log.

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Lastly would it be correct to assume that the sweet spot is towards the end of the "Stationary Phase"


I donít think so. There is no food of any type left for the yeast at the end of the stationary phase and they are just about to die. There is no meaningful yeast activity and certainly no fermentation. I would think any degassing would need to be done in the log phase. Once you get to the stationary phase, the yeast have produced all the CO2 they are going to produce and there will be no further inflation/rise. Where in the log phase to degas is probably a function of temperature.

AOTBE (i.e. for any particular fungus such as bakerís yeast), the shape of the growth curve in dough is largely determined by the temperature.  Commercial yeast (ADY, IDY, CY) is selected to be, among other things, fast, and the lag phase is relatively short at room temperature. Once you start to see visible activity in the dough, it has entered the log phase. Depending on the temperature, the log phase may be quite steep or almost flat, as would be the case in cold fermented dough.  When people talk about ďretardingĒ the dough, it means flattening out the growth curve by extending the log phase via low temperature. As long as your dough will still rise (if cold, it might need to be warmed), itís in the log phase. The stationary phase begins when all of the fermentable sugars have been exhausted and the yeast survive on stored products such as glycogen. Little or no CO2 is produced in the stationary phase, so rising has stopped. The yeast will remain in the stationary phase until all food sources are exhausted and the yeast begin to die.

At some point, enzymes will weaken the gluten to such a degree that water and gas will be released and the dough begin to get wet and collapse. This could happen in the log phase or stationary phase depending on factors such as temperature. As a general rule, the cooler the temperature, the earlier gluten breakdown will occur in the yeast growth cycle.

Here is a chart that illustrates yeast growth rate vs. temperature. It is for a sourdough culture, but the bakerís yeast curve would be similar to C. milleri though probably slightly more active at both ends.
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Offline 2stone

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Re: Fermentation Curve
« Reply #2 on: November 09, 2012, 02:13:32 PM »
Thanks for your detailed and quick response Craig,

Forgive me for being fast and loose with my terminology, I have switched out "Bacterial Growth Curve" with "Fermentation Curve" since bacteria sounds very unappetizing in this context.
The misconception I made when I first started baking 5 years ago is probably the same one a lot of people make regarding recipes being an end all blueprint. It turns out that mixing and fermentation procedures and protocols have way more to do with the final outcome than 1-2 % points of protein may have. Not being a chemist or a biologist I have a little of the same relationship to this subject as I do.... not wanting to know all the ins and outs of my computer hardware other than essentials needed to get my software to run properly.
As it turns out it is almost impossible to advance in baking without taking the time to understand some of the main principles involved.  

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I would think any degassing would need to be done in the log phase

When degassing the dough is it correct to assume that I would in effect be giving it a new food nutrient source that was formerly not in direct contact with the cell structures that were punctured, or am I just emptying out the tank (gluten walled pocket) and providing new room for more gas.

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I donít think so. There is no food of any type left for the yeast at the end of the stationary phase and they are just about to die

Is there something else changing during the stationary phase from beginning to end, or is it just in a stable limbo until it takes the nosedive. or is this where the gluten also starts degrading?

I"m at work and have to tend to some things but I really appreciate your detailed response and will digest it some more tonight.

regards
willard






« Last Edit: November 09, 2012, 02:16:37 PM by 2stone »
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Online TXCraig1

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Re: Fermentation Curve
« Reply #3 on: November 09, 2012, 03:13:59 PM »
When degassing the dough is it correct to assume that I would in effect be giving it a new food nutrient source that was formerly not in direct contact with the cell structures that were punctured, or am I just emptying out the tank (gluten walled pocket) and providing new room for more gas.

When you manipulate the dough, the agitation stimulates the yeast. The yeast is moved around away from waste products to new food, CO2 (a waste product and growth limiter) is removed, and some oxygen is added (yeast prefer an aerobic environment).

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Is there something else changing during the stationary phase from beginning to end, or is it just in a stable limbo until it takes the nosedive. or is this where the gluten also starts degrading?

Itís in limbo, but itís far from stable. During the early stages, the yeast synthesizes glycogen. They feed on this until enzymes break the starch into fermentable sugar. Some of the glycogen is stored.  When all the fermentable sugars are consumed, growth slows dramatically or stops and the yeast begins to metabolize the glycogen reserves to survive. Waste products accumulate to a point where they also limit growth.  This is the stationary period. Once the glycogen is depleted, the yeast will consume itself (autolysis).

The gluten breakdown is a result of the interplay of several factors and could happen during the log or stationary phase. It typically is not a problem with bakerís yeast other than with very long cold ferments. Sourdough is a different story.
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Offline 2stone

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Re: Fermentation Curve
« Reply #4 on: November 11, 2012, 12:09:48 PM »
That is an iteresting curve you posted. I have also found that the curve is completely different from CY IDY and a natural starter.

I'm looking at it in very simplistic terms......I was prodded by the master brewer at a brewery who also is a pizza enthusiast to look into many of the fermentation similarities between the two.

My overall interest in this is in trying to establish markers in the lag, log, and stationary phases.

For instance: http://redkart.com/cgi-bin/brew/ahbs/showstory.pl?s=newsletter&a=two_stage_ferm

In brewing they use a single and two stage process.....the 2 stage process could have some corresponding parallels to a biga / sponge / or poolish method.     -willard
« Last Edit: November 11, 2012, 12:11:19 PM by 2stone »
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Online TXCraig1

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Re: Fermentation Curve
« Reply #5 on: November 11, 2012, 03:36:09 PM »
That is an iteresting curve you posted. I have also found that the curve is completely different from CY IDY and a natural starter.


Just to be sure we are on the same page; the growth curve chart you posted is not the same as the growth rate at temperature chart I posted. The x-axis on the former is time, and it is temperature on the latter. I think you will find that the shape of the growth rate vs. temperature curve for a natural [sourdough] starter (typically Candida milleri or Saccharomyces exiguous yeast) is very similar to bakerís (and brewers) yeast (ADY, IDY, and CY Ė all strains of Saccharomyces cerevisiae). The difference is where the activity peaks; it is about 6-7C warmer for bakerís yeast. See the charts below (note on the second chart: ScT73 is a strain of S. cerevisiae used in winemaking).

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I'm looking at it in very simplistic terms......I was prodded by the master brewer at a brewery who also is a pizza enthusiast to look into many of the fermentation similarities between the two.


Pizza is not brewing or vice versa. While they both employ yeast fermentation Ė and generally the same species of yeast, both the growth medium and the objectives are very different.

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My overall interest in this is in trying to establish markers in the lag, log, and stationary phases.

For instance: http://redkart.com/cgi-bin/brew/ahbs/showstory.pl?s=newsletter&a=two_stage_ferm

In brewing they use a single and two stage process.....the 2 stage process could have some corresponding parallels to a biga / sponge / or poolish method.     -willard


Not to sound like a broken record, baking is not brewing. There are things you canít do in baking that you can in brewing Ė like remove the beer from the yeast waste products. I can see how having a mid-stage marker that will tell you when to do that could be important, but there is no corresponding activity in baking. Rather, the opposite is true, in large part, it is the waste and by products that deliver the flavor we are after.

To some extent, I use the stage breaks in my pizza making. I want to ball right at the onset of the log phase. This is easily identified when noticeable activity begins. But I donít go by visual cues. I know how long it takes to get there at my desired temperature.

I bake somewhere in the log phase (I know this because the dough is still expanding), but now itís a combination of intel that I use to get the dough ready when it needs to be ready. I know about how long it will take to get there at the desired temp, but thatís just a range. I also know how different temperatures will affect the growth rate (now Iím working off the growth vs. temp curve Ė not the growth curve). I can use visual cues  to make decisions about temperature adjustments, if necessary. The bottom line is that you need to know 1) what the dough looks like when it is ready, and 2) what changes to make if needed to get it ready on time.

I donít agree that biga, sponge, polish, etc. is analogous to or have parallels to a two-stage brewing process. As I noted above, you canít remove waste. If anything, itís just the opposite. You are trying to accumulate more waste that you otherwise could in a traditional direct method.

I would agree that there is sort of an inherent use of the growth curve in preparing a sourdough starter (and maybe a biga, sponge, polish, etc. Ė Iím not as familiar) for use. To have consistent results, itís important to use your starter at as close to the same activity level as possible every time. One place you can easily peg this is when the starter falls after post-feeding expansion.  I donít think you can say for sure if this is the onset of the death phase or rather somewhere in the stationary phase (and the gluten structure is weakened to a point where the structure collapses). My guess is the latter because it can be easily revived for days after falling. I suppose you could also try to use the end of the log phase (the starter stops expanding) as a reference point. Iíve heard many times that peak activity occurs right as the starter falls. I donít know if this is true or not. I tend to doubt it, and I donít think it matters. For me it's about consistency not a particular phase or marker.

While interesting as an intellectual exercise, I donít see an obvious practical value in baking akin to what you may have in brewing.

FWIW, there is a simple way to monitor the log phase; put two poppy seeds a measured distance apart on the surface of your dough. By measuring the increase in distance and employing a little math, you can tell how much your dough has expanded in volume. With a little calculus, you could determine the changes in rate and build a curve. You could even find some markers like the beginning of acceleration and deceleration. I just donít know what you would do with them after that. Though Iím curious to see what you come up with.


Pizza is not bread.

Offline La Sera

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Re: Fermentation Curve
« Reply #6 on: November 11, 2012, 06:30:29 PM »
Thanks for your interesting input, TXCraig1.

Cheers

Offline Jet_deck

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Re: Fermentation Curve
« Reply #7 on: November 11, 2012, 08:55:42 PM »
...To some extent, I use the stage breaks in my pizza making. I want to ball right at the onset of the log phase. This is easily identified when noticeable activity begins. But I donít go by visual cues. I know how long it takes to get there at my desired temperature.

And I want to bake this guy a pizzA?  :o
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Offline 2stone

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Re: Fermentation Curve
« Reply #8 on: November 12, 2012, 09:56:57 AM »
Craig,

You are disregarding the essence of my original post. I am referring to a broad description of fermentation as spelled out by the Department of Bioengineering, of Rice University as I indicated in the first post.....I'm sticking to my terminology.

Quote: "The basic process of fermentation has been used for centuries for producing a variety of foods around the globe.  Such examples include breads, beer, buttermilk, cheese, pickles, sauerkraut, yogurt, tempeh, just to name a few.  Up until the work of Louis Pasteur during the mid to late 1800s, little was know about the process of fermentation or the involvement of microorganisms.Fermentation is often defined as a process where cells produce energy anerobically, or without oxygen. In general, fermentation involves the breaking down of complex organic substances into simpler ones. Microbial or animal cells obtain energy through glycolysis, splitting a sugar molecule, and removing electrons in the process. The electrons are then passed to an organic molecule such as pyruvic acid. This results in the formation of waste products that are excreted from the cell. Waste products formed in this way include ethyl alcohol, butyl alcohol, lactic acid, and acetone."

I get asked all the time to recommend a good recipe for pizza. Many times I ask them if they know about pizzamaking.com.....and if not I tell them there's more information there than you could use in a life time. Some people find all of this information daunting, and many people just read and never join so they can't ask questions.

Pizza making is subjective. Style, recipe, yeast types, toppings, crust appearance, mixing protocols, fermentation protocols, dough handling, equipment preferences, mixers, ovens, dough containers just to name a few.

This can all be daunting for the first time pizza maker, (it was for me 5 years ago)

So to cut to the chase: recipes are great, but without mixing and fermentation protocols / schedules you will surely end up with mixed bag of results.

I still consider myself a "newbie" in most respects, and if I'm going up against a microbiologist or chemist, count me out. I have been on a quest to simplify (not oversimplify) the process, for myself and the people I deal with on a daily basis. Just because I'm popping the hood on my car, doesn't mean I'm willing to pull out the motor and disassemble it down to the last nut. (I would never get it back together again)

In some ways a hot oven (800-1000F) can be detrimental to the real understanding of good dough, since almost anything you put in the oven at those temperatures can easily come out looking like a beautiful hot air balloon.

If you back the temperatures down to 500-650F it can be a "reality check" on your dough making prowess, just as a "naked portafilter" is for the Barrista.

For the past two years I have been working on trying to understand the core principles of "hand mixing". Quality, repeatability and simplicity
were some of my main objectives. I may work up a shorter version and post it here, if I don't the process is posted in the link below. I browse Pizzamaking, Slice and PMQ to name a few.... here is my contribution if anyone would like to try it. (designed to work in any oven, especially at low temperatures)

http://2stoneblog.wordpress.com/2012/11/11/gustavsens-knife-trowel-protocol-for-hand-mixing-dough/

As you can see I have not gone into the "fermentation protocols" yet, but would like to get a better simplified (not oversimplified) handle on it some time.

below is the crumb structure of an 8 oz pizza dough ball baked at 550 F (instead of making a pizza out of it, I slid it onto some parchment paper, slit it a few times and baked it.
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FWIW, there is a simple way to monitor the log phase; put two poppy seeds a measured distance apart on the surface of your dough. By measuring the increase in distance and employing a little math, you can tell how much your dough has expanded in volume. With a little calculus, you could determine the changes in rate and build a curve. You could even find some markers like the beginning of acceleration and deceleration. I just donít know what you would do with them after that. Though Iím curious to see what you come up with.



Yes that is what I'm looking for.

Thanks for your diligent responses.

regards
willard
« Last Edit: November 12, 2012, 10:37:05 AM by 2stone »
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Online TXCraig1

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Re: Fermentation Curve
« Reply #9 on: November 12, 2012, 01:53:55 PM »
Craig,

You are disregarding the essence of my original post. I am referring to a broad description of fermentation as spelled out by the Department of Bioengineering, of Rice University as I indicated in the first post.....I'm sticking to my terminology.

Willard, Iím sorry; I wasn't trying to disregard the essence of my original post. I was only trying to restrict my focus to pizza (you did post this in the General Pizza Making section), clarify some misconceptions, and answer some of your questions. The quote you cited from my alma mater is about a subject much broader than the pizzamaking or baking, and most of it has no relevance to the topic at hand. Even something as closely related as the fermentation in brewing has little relevance.  As you noted, there is a lot of information here Ė so much that it can be daunting to some. For this reason, I donít understand why you want to expand beyond yeast fermentation and include bacterial and non-yeast fungal fermentations? Likewise, why complicate the relevant issues with growth mediums, substrates, process, etc. that have no bearing on pizza?

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So to cut to the chase: recipes are great, but without mixing and fermentation protocols / schedules you will surely end up with mixed bag of results.

I still consider myself a "newbie" in most respects, and if I'm going up against a microbiologist or chemist, count me out. I have been on a quest to simplify (not oversimplify) the process, for myself and the people I deal with on a daily basis. Just because I'm popping the hood on my car, doesn't mean I'm willing to pull out the motor and disassemble it down to the last nut. (I would never get it back together again)

Yes, my thoughts exactly Ė focus on what matters to pizzamaking. Those are the sorts of things I was trying to highlight in my previous posts. Understanding the 10 reactions that make up glycolysis is not going to help you make better pizza.  Nor, IMO, is likening baking to brewing where the substrate is completely different. Even knowledge of lactic acid fermentation will be of little benefit unless you are studying sourdough, and even then, I would think it would make sense to start your study of zymurgy with the most important organism in baking: S. cerevisiae (baker's yeast).

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In some ways a hot oven (800-1000F) can be detrimental to the real understanding of good dough, since almost anything you put in the oven at those temperatures can easily come out looking like a beautiful hot air balloon.

If you back the temperatures down to 500-650F it can be a "reality check" on your dough making prowess, just as a "naked portafilter" is for the Barrista.

I beg to differ. A NP-hot oven allows you to do things you canít in a home oven, but it does not magically fix problems in your dough or make you a better pizzaiolo. 500F or 1000F, the dough has to be right and right for the cooking environment, and the pizzaiolo must have some skills. Look at pictures WFO pizzerias across the country; the majority of the pies donít look very good.

The portafilter analogy doesnít fit. It would be more appropriate in the context of taking a guy who watches pies flow through the impinger oven at Dominoes, handing him a peel, and having him work a deck oven.

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As you can see I have not gone into the "fermentation protocols" yet, but would like to get a better simplified (not oversimplified) handle on it some time.

Iím not suggesting you oversimplify. With all due respect, I think you may be unintentionally overcomplicating something that is already immensely complicated.

Here are some things that come to mind that, if studied, could have application to baking:

- Study of the fermentation curve in terms of cumulative CO2 produced (as opposed to number of microorganisms which would be difficult to measure) vs. time (note that in this curve, there is no declining phase), and CO2 production rate vs. time;
- The effect of temperature on the shape of the curves, the stages, and sub-phases (e.g. acceleration and deceleration in the log phase);
- The effect of changes in the formula % yeast on the shape of the curves;
- How the shape of the fermentation curve affects flavor, texture, etc.;
- Effects of inoculating the dough with a population that is already in the log phase or beyond (i.e. biga, sponge, polish, etc.) and how temperature effects both the preferment and the final ferment;
- How deflating, reballing, baking, etc. at different points in the log phase affects the final product;
- Same questions post log.

Iím just trying to give you some things to think about. This is only a start. The changes in flour, hydration ratio, salt%, oil?, sugar? etc. all affect fermentation as well. As you can see, the fermentation problem, even in a tightly limited sense, is many orders of magnitude more complex than the study of mixing. Take and leave what you like. No worries.

Beautiful crumb on your loaf, BTW.

CL
Pizza is not bread.


Offline 2stone

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Re: Fermentation Curve
« Reply #10 on: November 13, 2012, 05:55:28 AM »
Mixing is the prelude to fermentation. It sets the stage for fermentation and impacts it more than some may think. In some cases they are running in tandem. There is more going on there than meets the eye.

Baking is the final act in the play. As the heat is increased, it becomes more and more dominant.  At some point it starts running ruff-shod over everything else. When something becomes too dominant it overshadows other things that can be of equal importance.

« Last Edit: November 13, 2012, 06:02:38 AM by 2stone »
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Online TXCraig1

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Re: Fermentation Curve
« Reply #11 on: November 13, 2012, 09:57:28 AM »
Mixing is the prelude to fermentation. It sets the stage for fermentation and impacts it more than some may think. In some cases they are running in tandem. There is more going on there than meets the eye.

Baking is the final act in the play. As the heat is increased, it becomes more and more dominant.  At some point it starts running ruff-shod over everything else. When something becomes too dominant it overshadows other things that can be of equal importance.



If you think I said fermentation is more important than mixing, you're reading things that I did not write. That the subject of fermentation is more complex does not diminish the importance of mixing; rather it provides opportunity. Genius in baking, like most things, lies in simplifying the complex.

I would argue that as the heat is increased, it is not the heat that becomes more dominant; problems in the dough become more dominant; problems with the oven become more dominant; and mistakes made by the pizzaiolo become more dominant.  When employing high heat, it is the shortcomings that run roughshod. If anything, proper application of high heat prevents the changes that occur during baking from becoming too dominant.

Pizza is not bread.

Offline 2stone

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Re: Fermentation Curve
« Reply #12 on: November 13, 2012, 10:48:32 AM »
Quote
I would argue

yes, I see......I'm not going to
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Re: Fermentation Curve
« Reply #13 on: November 13, 2012, 11:06:22 AM »
yes, I see......I'm not going to


A wise choice.
Pizza is not bread.

Offline mkevenson

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Re: Fermentation Curve
« Reply #14 on: November 13, 2012, 10:14:06 PM »
Craig and Willard, thanks for this post. The info you have both brought has given me insights into pizza making that I never realized I didn't know. I sense a bit of ........ Animosity at times in the replys. I hope that you both are willing to share your knowledge with us, the uneducated masses, in a constructive way.
I know that it takes a long time for me to write my meager posts, so I do appreciate you both taking the time to discuss the finer points of fermentation.
I wonder if you got together in a less formal format than the forum, if you would find more common ground?
Be that as it may, thanks for the education.

Mark
"Gettin' better all the time" Beatles