Author Topic: fermentation  (Read 11092 times)

0 Members and 1 Guest are viewing this topic.

Offline IEatPizzaByThePie

  • Registered User
  • Posts: 56
  • Location: Nomville, ZA
  • ohaipizza OM NOM NOM NOM NOM NOM NOM OM NOM NOM
fermentation
« on: January 16, 2007, 04:08:02 PM »
I've made a good number of pizzas, and I can definitely say that I prefer the taste of retarded dough that has fermented for a good 3 days. That is compared to dough fermented for 6-8 hours, 24 hours and 48 hours.

My question is, what exactly is the resulting difference between a dough that ferments for, say, 8 hours at room temp and has risen to double its original size, and a dough that ferments refrigerated for 3 days and has doubled in size? Does the fermentation occur more "thoroughly" in dough that uses a slow ferment even though the rise appears to be the same?
"I looked at the serving size: two slices. Who the hell eats two slices? I eat pizza by the pie! Two pies is a serving size!!"


Offline LabRat

  • Registered User
  • Posts: 21
  • I Love Pizza!
Re: fermentation
« Reply #1 on: January 16, 2007, 05:01:50 PM »
My understanding is that retarding the dough slows down yeast fermentation, which allows amylase and other enzymes naturally present in flour more time to break down starch molecules in to various sugars and perform other functions.  Bacteria also present in the flour are adding their own fermentation products (like acids) during this time, but if you let it go too long they take over and create an environment in which bakers yeast can not survive.  The wild yeast in San Francisco sourdough starter actually prefer the acidic environment created by the various bacteria.

Offline SemperFi

  • Registered User
  • Posts: 152
  • Age: 42
  • Getting there, slowly but surely
Re: fermentation
« Reply #2 on: January 16, 2007, 09:05:55 PM »
Ieatpizzabythepie,

You might want to check out this thread by Pete-zza.  He is extremely knowledgeable on pizza doughs.

http://www.pizzamaking.com/forum/index.php/topic,1523.msg13899.html#msg13899

Hope it helps.
Adam
Adam

Offline Pete-zza

  • Lifetime Member
  • Global Moderator
  • *
  • Posts: 23446
  • Location: Texas
  • Always learning
Re: fermentation
« Reply #3 on: January 16, 2007, 09:17:40 PM »
Adam,

Thank you very much but the guy who really knows what is going on inside a dough ball is November :).

It was interesting to read the thread you referenced because at the time many of us were having difficulties getting more than three days out of a Lehmann NY style dough. More recently, with the help of November and others, I have been able to make doughs that have a useful life of 6-12 days. The details, along with photos, are presented at this thread: http://www.pizzamaking.com/forum/index.php/topic,3985.msg33251.html#msg33251.

Peter

Offline SemperFi

  • Registered User
  • Posts: 152
  • Age: 42
  • Getting there, slowly but surely
Re: fermentation
« Reply #4 on: January 16, 2007, 09:22:34 PM »
Peter,

Your welcome, I do believe that you deserve kudos though.  I had actually just scanned that thread, then did another search, and came up with the thread that I posted.  Both are excellent threads though.  Its amazing, I just keep searching every thought that comes to mind, and there you are..with a post.   :-D  Thanks again for the additional info Peter.

Adam
Adam

Offline IEatPizzaByThePie

  • Registered User
  • Posts: 56
  • Location: Nomville, ZA
  • ohaipizza OM NOM NOM NOM NOM NOM NOM OM NOM NOM
Re: fermentation
« Reply #5 on: January 17, 2007, 04:05:49 AM »
Thanks for the replies.

Yes, I'm very away that Pete is extremely knowledgeable  ;D
After spending any amount of time on these boards it quickly becomes apparent that this guy is a natural born pizza wiz! Like you, his posts always seem to turn up in my searches (that's a good thing!)

Anyway, I will have to experiment with that 5-6 day Lehmann recipe in that thread. I've made the original Lehmann NY recipe already, but it only refrigerated for 24 hours. It was good, but personally I enjoyed Big Dave's Old Faithful more.
"I looked at the serving size: two slices. Who the hell eats two slices? I eat pizza by the pie! Two pies is a serving size!!"

Offline November

  • Registered User
  • Posts: 1892
  • Location: North America
  • Come for the food. Stay for the science.
    • Uncle Salmon
Re: fermentation
« Reply #6 on: January 17, 2007, 05:48:29 AM »
Thanks, Peter.  When I first saw the question, I hesitated answering because of how subjective flavor can be.  A lot of people swear by cold-fermentations; I don't.  This topic depends on so many things it's not even funny.  (Okay, maybe it is sometimes.)  This is by no means a comprehensive answer on the subject, but here are a few important points, some of which LabRat mentioned already.

Bacteria convert malic acid excreted by yeast into more pleasant tasting lactic acid, and bacteria are more active than yeast at lower temperatures.  Acetic acid bacteria also convert flavorless ethanol to acetic acid.  However, if the yeast are not producing these chemicals at a very fast rate because of the cold, the bacteria aren't going to be doing their job as actively as they could.  Also, alpha-amylase enzymes, like all enzymes, are almost as inactive in the cold as yeast.  If you want to know more specifically how active the enzymes are with any given condition, search for the Arrhenius equation (an equation used in Chemistry to determine reaction kinetics).

For maximum flavor the trick is, as most chemistry experiments go, to find the reaction stoichiometry between bacteria, enzyme, and yeast activity.  You want the dough at just the right temperature so that they all play their important roles harmoniously.  It's not as easy as just putting the dough in an average household refrigerator.  How much bacteria you have in your dough, the falling number of your flour, the strain of your yeast, and the micro-nutrients you (purposely or inadvertently) feed your yeast all have more to do with flavor than the temperature itself.  Cold fermentation has house odds only because of its near fool-proof procedure.  When doughs can go as long as a week in the refrigerator, pulling it out to use a few hours late isn't going to have much effect.  The same cannot be said about room temperature dough.  One has to be more careful with what goes in the dough, and when to use the dough.

- red.november

Offline SemperFi

  • Registered User
  • Posts: 152
  • Age: 42
  • Getting there, slowly but surely
Re: fermentation
« Reply #7 on: January 17, 2007, 06:27:10 AM »
Wow, Pete-zza was right when he said:

Thank you very much but the guy who really knows what is going on inside a dough ball is November .




Bacteria convert malic acid excreted by yeast into more pleasant tasting lactic acid, and bacteria are more active than yeast at lower temperatures....  Also, alpha-amylase enzymes, like all enzymes, are almost as inactive in the cold as yeast.  If you want to know more specifically how active the enzymes are with any given condition, search for the Arrhenius equation (an equation used in Chemistry to determine reaction kinetics).

- red.november
Adam

Offline IEatPizzaByThePie

  • Registered User
  • Posts: 56
  • Location: Nomville, ZA
  • ohaipizza OM NOM NOM NOM NOM NOM NOM OM NOM NOM
Re: fermentation
« Reply #8 on: January 17, 2007, 06:52:17 PM »
Thanks for that post November, very informative. A lot seems to be going on during fermentation that many people probably don't know about.

So, is there any reason why I couldn't just take a given recipe, lower the amount of yeast some, and then refrigerate the dough longer to achieve a slower rise? Like a 3 day rise instead of just 24 hours maybe? If this is possible, would anything else need to be altered to compensate for the longer rise time (such as other ingredients like the amount of water)?
"I looked at the serving size: two slices. Who the hell eats two slices? I eat pizza by the pie! Two pies is a serving size!!"


Offline November

  • Registered User
  • Posts: 1892
  • Location: North America
  • Come for the food. Stay for the science.
    • Uncle Salmon
Re: fermentation
« Reply #9 on: January 17, 2007, 07:28:19 PM »
IEatPizzaByThePie,

The length of fermentation, whether cold or room temperature, is always determined by what you have in your dough that will help sustain the yeast.  This includes several things, the most basic of which is nutrients.  Simple nutrients like sugars are obviously needed, whether added by you or converted by enzymes.  You'll likely want to use a little less salt than a room temperature dough formula, because although the yeast already slow down because of the lower temperature, enzymes are even more inhibited by salt.  If you're planning on a really long fermentation, use sea salt so that additional micro-nutrients are available to the yeast for cell maintenance; and if you use sugar, use one with minerals like zinc, magnesium, or phosphorous (e.g. brown sugar, maple sugar, raw cane sugar, honey).  Depending on the condition of your flour, you can probably sustain a small amount of yeast (0.25% or less) for about a week at 41 F with no additional nutrients.  For a three day rise, you shouldn't have to do anything but use less yeast.

How the dough is stored in your refrigerator will make a difference too.  Ideally during a long, cold rise, you want the excess gas to escape, but not the moisture.  During a 24 hour rise, keeping it completely sealed is fine.  Storing the dough in a plastic container (as opposed to metal or glass) will spare the surface of the dough from extreme temperature gradients.  If your refrigerator is really cold like mine, where the temperatures reach 32 F or below near the back, double-up your container.

- red.november
« Last Edit: January 17, 2007, 07:30:11 PM by November »

Offline IEatPizzaByThePie

  • Registered User
  • Posts: 56
  • Location: Nomville, ZA
  • ohaipizza OM NOM NOM NOM NOM NOM NOM OM NOM NOM
Re: fermentation
« Reply #10 on: January 18, 2007, 08:26:48 AM »
Hey November,

That makes good sense. You mentioned letting the gases escape during a lengthy cold rise. How would you recommend going about this? Would just uncovering the container for a few seconds every day get the job done?
"I looked at the serving size: two slices. Who the hell eats two slices? I eat pizza by the pie! Two pies is a serving size!!"

Offline David

  • Registered User
  • Posts: 966
  • What’s So Funny ‘Bout Pizza Love and Understanding
Re: fermentation
« Reply #11 on: January 18, 2007, 09:13:13 AM »
Bacteria convert malic acid excreted by yeast into more pleasant tasting lactic acid, and bacteria are more active than yeast at lower temperatures.  Acetic acid bacteria also convert flavorless ethanol to acetic acid.  However, if the yeast are not producing these chemicals at a very fast rate because of the cold, the bacteria aren't going to be doing their job as actively as they could.  Also, alpha-amylase enzymes, like all enzymes, are almost as inactive in the cold as yeast.  If you want to know more specifically how active the enzymes are with any given condition, search for the Arrhenius equation (an equation used in Chemistry to determine reaction kinetics).

For maximum flavor the trick is, as most chemistry experiments go, to find the reaction stoichiometry between bacteria, enzyme, and yeast activity.  You want the dough at just the right temperature so that they all play their important roles harmoniously.  It's not as easy as just putting the dough in an average household refrigerator.  How much bacteria you have in your dough, the falling number of your flour, the strain of your yeast, and the micro-nutrients you (purposely or inadvertently) feed your yeast all have more to do with flavor than the temperature itself.  Cold fermentation has house odds only because of its near fool-proof procedure.  When doughs can go as long as a week in the refrigerator, pulling it out to use a few hours late isn't going to have much effect.  The same cannot be said about room temperature dough.  One has to be more careful with what goes in the dough, and when to use the dough.

- red.november

Thanks for this insight red.november .I have to say I often have a difficult time getting my head around the mathematical  / scientific side of Pizza making and as such my progress is somewhat sloth like.Particularly as someone who only uses room temp.rises / natural starters,I would value you input and  knowledge of any experimentation on the maculation of the crust that you would wish to share?It is a subject that has been touched on in the past,but without any significant explanations IMO.
                                                                               David

If you're looking for a date... go to the Supermarket.If you're looking for a wife....go to the Farmers market

Offline Pete-zza

  • Lifetime Member
  • Global Moderator
  • *
  • Posts: 23446
  • Location: Texas
  • Always learning
Re: fermentation
« Reply #12 on: January 18, 2007, 09:25:10 AM »
November,

I understand that there are also nutrients in water that are used by the yeast. Is there any particular form of water (e.g., spring, tap, bottled, etc.) that is preferred? I know that many pizza operators, especially the big ones, use water purification systems. What aspects of the water are they treating?

The municipal water where I live is on the hard side, with a pH on the high side. I have read that using a bit more yeast can compensate. Does that make sense?

Thanks.

Peter

Offline November

  • Registered User
  • Posts: 1892
  • Location: North America
  • Come for the food. Stay for the science.
    • Uncle Salmon
Re: fermentation
« Reply #13 on: January 18, 2007, 12:12:49 PM »
IEatPizzaByThePie,
You could do that if you're dedicated enough.  If it's just a cheap container, you could also drill a tiny hole (1-2 mm) near the lid and be sure your dough ball is oiled.

David,
I'm not sure what you mean.  Are you talking about blisters?  If so, that's been covered in another thread.  If you're talking about some other kind of lesion or surface effect, you'll have to explain further.

Peter,
Tap water is too much of an unknown and not considered a control.  For chemistry experiments at least, a chemist always starts with distilled water and adds what he needs.  In the case of pizza making, I always start with filtered water and add what I need.  Hard water has lots of minerals, but in most places they are mostly calcium and iron which yeast don't really need (at least until they develop hemoglobin and a skeletal structure).  If you weren't planning on adding sodium salt (table salt), calcium chloride (not calcium oxide) from hard water would then, and only then, be a benefit.  Spring water is a great option, since there shouldn't even be trace amounts of chlorine or fluorine.  Reverse osmosis filtering eliminates mineral content and reduces the number of larger microorganisms.  If the filtration system has a carbon post-filter, halogens are also reduced.  A water filter pitcher (like what I use) reduces mostly halogens and only part of the minerals.  I prefer filtered over bottled, because unless I run an analysis on the bottled water, I don't really know what's in it.  Yeast want a low pH (acidic), and the best range is around 4.2-4.6.

- red.november

Offline David

  • Registered User
  • Posts: 966
  • What’s So Funny ‘Bout Pizza Love and Understanding
Re: fermentation
« Reply #14 on: January 18, 2007, 12:32:36 PM »


David,
I'm not sure what you mean.  Are you talking about blisters?  If so, that's been covered in another thread.  If you're talking about some other kind of lesion or surface effect, you'll have to explain further.


- red.november

Yes.Leopard spots.I've seen pizzas with pale (In comparison to the rest of the cornicione) blisters but this is not what I'm talking about.The charred spotting that is so prominent against the pale dough as found in true Neapolitan pizza.I'm wondering if this is more due to the intense heat ,dough management,or a combination of factors?
If you're looking for a date... go to the Supermarket.If you're looking for a wife....go to the Farmers market

Offline November

  • Registered User
  • Posts: 1892
  • Location: North America
  • Come for the food. Stay for the science.
    • Uncle Salmon
Re: fermentation
« Reply #15 on: January 18, 2007, 12:57:56 PM »
David,

Charing is a result of intense or prolonged heat.  The fact that it's spotted just indicates that some parts of the dough dry out sooner than others.  That can happen due to several factors, the most prevalent of which is dynamically constant circulating heat over turbulent surfaces.  The pizza crust is not perfectly smooth.  Where there are very small (almost naked to the eye) cavities, a boundary layer is created and prevents the hotter, circulating air from reaching it.  Hotter circulating air and radiant heat can more effectively penetrate places on the crust where there are small protrusions.

- red.november

Offline scott r

  • Supporting Member
  • *
  • Posts: 3101
  • Age: 44
  • Location: boston
  • I Love Pizzafreaks!
Re: fermentation
« Reply #16 on: January 18, 2007, 01:40:20 PM »
November,  have you read Baking science and technology by E. J Pyler?

I was thinking about picking it up for some light sunday reading.  ;D

Just wondering if you have any comments about it.


Offline November

  • Registered User
  • Posts: 1892
  • Location: North America
  • Come for the food. Stay for the science.
    • Uncle Salmon
Re: fermentation
« Reply #17 on: January 18, 2007, 02:19:08 PM »
scott,

No, I have not.  I had a formal education in biology, chemistry, and physics and only keep references like the "CRC Handbook of Chemistry and Physics" around.  When I want to focus on a specific discipline within one of those sciences, I turn to research publications because they are generally more up-to-date.  Publications from authors like Dr. T. van Vliet (http://www.wewur.wur.nl/wewur/visitecard.cfm?o_nummer=14942) are what pique my interest.  Read through his entire list of publications and you'll see what kind of level I like to play on.  I get most of my publications from ScienceDirect, and more specifically from the Journal of Cereal Science (http://top25.sciencedirect.com/?journal_id=07335210) for dough related research; and from Blackwell Synergy (http://www.blackwell-synergy.com/).

I'm sure "Baking Science and Technology" is a good book.

- red.november

Offline scpizza

  • Registered User
  • Posts: 317
  • Demystifying Neapolitan Pizza
Re: fermentation
« Reply #18 on: February 10, 2007, 11:05:04 AM »
This is a good discussion.  November, do you have any insights on the optimal rise temperature (for flavor) for the Ischia and/or Camaldoli starters using Caputo 00 Pizzeria?

One way I recently tried to improve flavor is by attempting to increase lactic acid production.  I did this by incubating my starter through several washings at 33C.  According to the temperature graphs in Ganzle, et. al. this should shift the population in favor of L. Sanfranciscensis over C. Milleri.  Indeed the resultant culture smelled non-yeasty and dull-sour.

Unfortunately dough made with the culture, rising at 25C, showed no improvement in taste and actually lacked flavor.  I wonder if the interdependencies between the two organisms, such as the malic acid link you mention, kept the LAB from doing anything in excess of the proportion of yeast and thus defeated my skewing of the population.

I am also vexed by conflicting information in regards to the favorability of lactic vs. acetic acid for improved flavor.  Some information says lactic acid is preferable in that its non-volatility means it doesn't evaporate at baking; plus the lactic taste is more appealing than the acetic vinegary taste.  Other information points out the tongue is not where the complex tastes are registered; it's actually the nose, and thus the volatile compounds like acetic acid are preferable over lactic acid.  What are your thoughts?
« Last Edit: February 10, 2007, 11:13:17 AM by scpizza »

Offline AKSteve

  • Lifetime Member
  • *
  • Posts: 141
  • We are all made from the same dough.
Re: fermentation
« Reply #19 on: February 11, 2007, 02:03:48 AM »
Anyone,

Any ideas on what effect the longer fermentation period has on the glycemic index of the dough? I'm a Type I diabetic and I've noticed that the pizza I make at home raises my bloodsugar much less than pizza from the local shops. I'm sure there are many other variables in play like pizza-sauce ingredients, thickness of the crust, etc. Plus the fact that I'm running around burning calories doing all of the cooking rather than waiting for the pizza to be delivered. I'm just wondering whether a 3 day+ cold fermentation would use up more of the starch in the dough compared to a quick room-temperature rise.

Steve

Offline November

  • Registered User
  • Posts: 1892
  • Location: North America
  • Come for the food. Stay for the science.
    • Uncle Salmon
Re: fermentation
« Reply #20 on: February 12, 2007, 01:56:21 PM »
November, do you have any insights on the optimal rise temperature (for flavor) for the Ischia and/or Camaldoli starters using Caputo 00 Pizzeria?

I don't have anything specific to report about optimal temperatures for starters.  I've always handled my starters (when I use them, which is very rare) the same way as my dough with regard to temperature.  With the finer granularity of 00 flour, less work is needed by the enzymes to convert the starch to simple sugars, so you can get away with lower temperatures using 00 flour relative to other flours.  I've spent a lot more time with preferments than what are generally referred to as starters, as I'm only performing the extra work for better flavor.  I don't like to catch wild yeast, or keep the same dough around for the purpose of starting subsequent batches.

One way I recently tried to improve flavor is by attempting to increase lactic acid production.  I did this by incubating my starter through several washings at 33C.  According to the temperature graphs in Ganzle, et. al. this should shift the population in favor of L. Sanfranciscensis over C. Milleri.  Indeed the resultant culture smelled non-yeasty and dull-sour.

With respect to one bacteria over another, that's fine.  However, with respect to bacteria over yeast, depending on how much yeast you have in your starter, that's not usually the case.  As has been mentioned several times before, bacteria can thrive at temperatures below the comfort zone for yeast, so keeping the dough cool (as in 5 C) accomplishes your goal in the long run.  That's why food can still spoil even if kept in the refrigerator.  You may want to keep your yeast away from your starter when you have the starter at 33 C, or use extremely miniscule amounts.  The more acetic acid that is produced by the yeast, the less your bacteria will be able to function.

Unfortunately dough made with the culture, rising at 25C, showed no improvement in taste and actually lacked flavor.  I wonder if the interdependencies between the two organisms, such as the malic acid link you mention, kept the LAB from doing anything in excess of the proportion of yeast and thus defeated my skewing of the population.

Lactic acid contributes, by most people's standards, a better flavor, but acetic acid is by far a stronger acid in terms of palate sensitivity.  It's like the salt of acids.  A little bit goes a long way to enhance flavor.  By lowering your temperature to 25 C, you created conditions where comparatively speaking, less acetic acid is produced.  At the same time, less malic acid would be produced also, but keep in mind that yeast produces very little malic acid compared to acetic acid.  Since each person has their own subjective flavor preference, you apparently found a region near 30 C, with whatever amount of yeast you used, that produces the mix of acids (and related organic compounds) that are favorable to you.

I am also vexed by conflicting information in regards to the favorability of lactic vs. acetic acid for improved flavor.  Some information says lactic acid is preferable in that its non-volatility means it doesn't evaporate at baking; plus the lactic taste is more appealing than the acetic vinegary taste.  Other information points out the tongue is not where the complex tastes are registered; it's actually the nose, and thus the volatile compounds like acetic acid are preferable over lactic acid.  What are your thoughts?

First of all, lactic acid and acetic acid are both carboxylic acids with similar boiling points, so the evaporation at baking will also be similar, with acetic having only a slightly higher evaporation rate.  Due to acetic acid's smaller molecular weight, it is more penetrating and aromatic than lactic.  That's one of the reasons why our sensitivity is higher with acetic.  It's been well studied and documented that flavor is approximately half odor and half taste.  There are a lot of biochemical registers that are set off as a result of smelling your food.  It has long been believed that people ingest more when their food is cold, because the lower temperature prevents certain aromatic compounds from evaporating from the food, and triggering a response in the brain telling it how much food they've even.  Refrigeration was an invention of man, so our bodies aren't designed to deal with the consumption of food at temperatures less than around 20 C.  The effect is minimal for some people, but it's there at some level for everybody.  That's why a lot of people report being able to eat a whole box of cereal (with cold milk) before getting full.  There are few aromatic compounds in cereal to begin with, and eating it with cold milk exaggerates the effect.  So, I said that to say this, acetic acid does register with the senses (gustation and olfaction) more than lactic acid, but more so with gustation (taste).

I get around the whole idea of trying to get bacteria to produce lactic acid for me by using food products like soy butter, or my favorite so far, "Better Than Cream Cheese" by Tofutti.  The lactic acid they add to soy products like this is produced by bacteria simply fed cane sugar.  Since these products lack lactose or other milk solids, they don't taste exactly like dairy, but instead have a generic cheesy/buttery flavor which compliments pizza dough very well.  It's essentially what you're looking for but without all the work.  The primary fat is soybean oil, so I usually use about 20-30g soy cream cheese with 7-10g of olive oil or rice bran oil for a total of 10-15g total oil in a 900-1000g dough batch.  Because of this process, I rarely use preferments anymore.  Some may consider that cheating, but by some standards, so is letting someone else grow your wheat and mill it for you too.

- red.november

Offline scpizza

  • Registered User
  • Posts: 317
  • Demystifying Neapolitan Pizza
Re: fermentation
« Reply #21 on: February 12, 2007, 06:54:00 PM »
You may want to keep your yeast away from your starter when you have the starter at 33 C, or use extremely miniscule amounts.

Thanks for your response, however, it is confusing to me.  We may be defining terms differently.  I'm defining "starter" (Ischia in this case) as a culture containing both bacteria (L. Sancrancisenis) and yeast (C. Milleri).  There is no other yeast involved in my experiment other than the C. Milleri cells present in my starter.

Agreed that culturing at 5C will favor bacteria at the expense of yeast, but so will culturing at 33C.  At either temperature after several refreshments the yeast should be in the minority in the starter by my reckoning. 

Also I don't agree with your comment that by lowering the temperature from 33C to 25C less lactic acid is produced.  At 25C the bacteria and yeast grow at about the same rate.  It is at temps from 25C-40C that the bacteria grow faster.

Even though I cultured my starter at 33C, I rose my dough at 25C because I figured the starter was so heavily skewed to the bacteria side to start with, that letting the bacteria and yeast yeast rise at 25C would simply keep that imbalanced state preserved as each bug grew at the same rate.  I didn't want to obliterate the yeast entirely.

Plus I read somewhere that no cell division happens in the anaerobic environment of the dough, that oxygen is required for that, though of this I am not very confident.

I am still not sure why my experiment skewing the starter cell population toward the lactic bacteria did not produce the stronger lactic acid taste I was hoping it would.

Thanks for your perspective on the lactic vs acetic acid taste question.  I didn't appreciate the different chemical properties of each.  Fascinating story about refrigerated food lacking the same taste as room temp food.  Wonder why cold pizza tastes so good then? :)

And yes, your addition of lactic acid saturated foodstuffs to pizza dough is total cheating!

Offline November

  • Registered User
  • Posts: 1892
  • Location: North America
  • Come for the food. Stay for the science.
    • Uncle Salmon
Re: fermentation
« Reply #22 on: February 12, 2007, 08:11:19 PM »
Thanks for your response, however, it is confusing to me.  We may be defining terms differently.  I'm defining "starter" (Ischia in this case) as a culture containing both bacteria (L. Sancrancisenis) and yeast (C. Milleri).  There is no other yeast involved in my experiment other than the C. Milleri cells present in my starter.

I was talking about starters in general.  Again, I don't know how much yeast is in your starter, but in general, at that temperature yeast will be active enough to consume the nutrient supply to such a degree that bacterial activity will be impaired.

but so will culturing at 33C.

Not without provisions, at that temperature the yeast will be quite active.  Growth rates don't necessarily translate to metabolic exchange rates.  Just because the optimum temperature for C. Milleri is about 27 C, and 33 C for L. Sancrancisenis, it doesn't mean you will achieve a dough with a disproportionately larger quantity of lactic acid.  Because of how much more yeast consumes on a per-cell basis, the minor growth rate difference at 33 C will not not be enough to allow the bacteria to thrive as much in the presence of yeast.  If your culture has a significantly small amount of C. Milleri, or your washing is effective in meeting your desired end, then you're set to incubate at 33 C.

Also I don't agree with your comment that by lowering the temperature from 33C to 25C less lactic acid is produced.

Your disagreement is misplaced.  I never said less lactic acid is produced; nevertheless, assuming bacteria is less active at 25 C versus 33 C, I don't see from where the source of your disagreement stems.

At 25C the bacteria and yeast grow at about the same rate.  It is at temps from 25C-40C that the bacteria grow faster.

Growth at the same rate, yes, but not necessarily produce the respective acids at the same rate; and even that is assuming the nutrient supply holds up for both.

Plus I read somewhere that no cell division happens in the anaerobic environment of the dough, that oxygen is required for that, though of this I am not very confident.

That is not exactly correct.  Yeast budding happens at a greatly decreased rate in an anaerobic environment, but it doesn't stop entirely.

Wonder why cold pizza tastes so good then? :)

Although I eat cold pizza on very regular basis, I would have to say that is a matter of opinion.

And yes, your addition of lactic acid saturated foodstuffs to pizza dough is total cheating!

So be it.  I don't have a problem with experimentation for the sake of gaining knowledge, but I have better things to do than spend time on starters all the time.  I'm sure there are many who think buying yeast cultures is cheating.

- red.november

Offline scpizza

  • Registered User
  • Posts: 317
  • Demystifying Neapolitan Pizza
Re: fermentation
« Reply #23 on: February 12, 2007, 09:50:05 PM »
Growth rates don't necessarily translate to metabolic exchange rates.  Just because the optimum temperature for C. Milleri is about 27 C, and 33 C for L. Sancrancisenis, it doesn't mean you will achieve a dough with a disproportionately larger quantity of lactic acid.  Because of how much more yeast consumes on a per-cell basis, the minor growth rate difference at 33 C will not not be enough to allow the bacteria to thrive as much in the presence of yeast.
Even if the yeast consume far more on a per-cell basis, shouldn't the lactic acid / acetic acid ratio increase if you get more L. Sanfranciscensis cells?

It seems you are saying even though the L. Sanfranciscenis is growing disproportionately faster at 33C than C. Milleri, we still don't see a higher lactic acid / acetic acid ratio because the yeast cells that are there are much more metabolically efficient at 33C than 25C and thus able to hog the sugars even in the face of increasingly larger numbers of L. Sanfranciscenis.

I have assumed that replication rate changes are proportional to metabolic rate changes.  Replication is directly linked to energy availability is directly linked to metabolic rate is directly linked to by-product production.  If that assumption is mistaken, then I can see why I might not get a greater lactic acid / acetic acid ratio at the higher temperature.

I do see you agree with me that at some point after enough washings the C. Milleri would just be so numerically overwhelmed by the L. Sanfranciscenis that I could then achieve the higher lactic acid / acetic acid ratio.

Your disagreement is misplaced.  I never said less lactic acid is produced; nevertheless, assuming bacteria is less active at 25 C versus 33 C, I don't see from where the source of your disagreement stems.
I was disagreeing with your statement that "By lowering your temperature to 25 C, you created conditions where comparatively speaking, less acetic acid is produced."  Does "comparatively" mean compared to acetic acid at 33C or to compared to lactic acid?  I definitely agree with the former.  But as I mention above, the latter is very counterintuitive.

That is not exactly correct.  Yeast budding happens at a greatly decreased rate in an anaerobic environment, but it doesn't stop entirely.
This makes sense to me.  From a survival basis it just makes sense that both of these bugs need to be able to replicate in an anaerobic environment.
« Last Edit: February 12, 2007, 09:55:09 PM by scpizza »

Offline November

  • Registered User
  • Posts: 1892
  • Location: North America
  • Come for the food. Stay for the science.
    • Uncle Salmon
Re: fermentation
« Reply #24 on: February 12, 2007, 11:23:10 PM »
Even if the yeast consume far more on a per-cell basis, shouldn't the lactic acid / acetic acid ratio increase if you get more L. Sanfranciscensis cells?

You're assuming that the L. Sanfranciscensis cell count increases at an optimal rate in the presence of yeast.  It doesn't.  Both its growth and metabolic exchange rate is very much dependent on the nutrient supply - a supply which the yeast competes for.  Yet again I stress that all of this still depends on what the initial cell count ratio is between the yeast and bacteria.  If the bacteria are outnumbered to begin with, there isn't much room for bacterial activity, metabolic or growth.

It seems you are saying even though the L. Sanfranciscenis is growing disproportionately faster at 33C than C. Milleri, we still don't see a higher lactic acid / acetic acid ratio because the yeast cells that are there are much more metabolically efficient at 33C than 25C and thus able to hog the sugars even in the face of increasingly larger numbers of L. Sanfranciscenis.

Once again, it comes down to the initial ratio between the two and nutrient availability, but also washings over time.

I have assumed that replication rate changes are proportional to metabolic rate changes.  Replication is directly linked to energy availability is directly linked to metabolic rate is directly linked to by-product production.

That is not a solid assumption to make.  Waste products from organisms at any level of complexity change variably with stages of life.  You can tell the difference between the fecal matter and urine from a human infant, 30-year-old, pregnant mother, and dying 85-year-old, because when an organism is growing, maintaining, reproducing, or dying, it is producing a different kind of waste.  The cell growth and reproductive processes also absorb compounds and reserve producing certain chemicals that would not necessarily happen in cases of cell maintenance or dying.  Reproduction is also directly linked to acidity for bacteria, which does not affect metabolism in the same way.

I do see you agree with me that at some point after enough washings the C. Milleri would just be so numerically overwhelmed by the L. Sanfranciscenis that I could then achieve the higher lactic acid / acetic acid ratio.

It could take a lot of washings though.

I was disagreeing with your statement that "By lowering your temperature to 25 C, you created conditions where comparatively speaking, less acetic acid is produced."  Does "comparatively" mean compared to acetic acid at 33C or to compared to lactic acid?  I definitely agree with the former.  But as I mention above, the latter is very counterintuitive.

I don't see how it matters what I was comparing.  I said less acetic acid, not less lactic acid.  Even if I were comparing it to the lactic acid, that doesn't mean there's less lactic acid.  In fact, it would imply there's more lactic acid relative to acetic acid.  Anyway, you were comparing the results between two temperatures, so I followed suit.  However, I still don't know why you object to there being less lactic acid as a result of a lower temperature.  The comparison has remained between 25 C and 33 C results.

- red.november