Author Topic: Compressed Yeast to make a Starter?  (Read 1618 times)

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Offline Wazza McG

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Compressed Yeast to make a Starter?
« on: December 07, 2013, 07:53:59 PM »
Hi,

I was wondering whether you could make a starter out of fresh compressed yeast and keep it alive forever as you can with other starters? The Deli up the road changed hands and has now got fresh compressed yeast available.

Cheers
Warren
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Offline norma427

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Re: Compressed Yeast to make a Starter?
« Reply #1 on: December 07, 2013, 10:11:27 PM »
Hi,

I was wondering whether you could make a starter out of fresh compressed yeast and keep it alive forever as you can with other starters? The Deli up the road changed hands and has now got fresh compressed yeast available.

Cheers
Warren

Warren,

I played around a little when with a starter made with Cake yeast, water and molasses.  If you want to read more about that the thread is at http://www.pizzamaking.com/forum/index.php/topic,16884.msg164510.html#msg164510  Chau also posts about his Cake yeast starter at Reply 4 http://www.pizzamaking.com/forum/index.php/topic,16884.msg164522.html#msg164522 and helps me on my thread.

I also posted at Reply 1090 http://www.pizzamaking.com/forum/index.php/topic,9908.msg165002.html#msg165002 about using the cake yeast starter to leaven pizza dough and those results are at Reply 1094 http://www.pizzamaking.com/forum/index.php/topic,9908.msg165153.html#msg165153

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Online Pete-zza

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Re: Compressed Yeast to make a Starter?
« Reply #2 on: December 08, 2013, 02:07:06 PM »
Warren,

To get the full picture on this matter, the thread that I think you should read is Chau's thread, including the posts referenced therein, starting at http://www.pizzamaking.com/forum/index.php/topic,12824.0.html. In that thread, Chau starts to talk about trying to make a commercial starter and perpetuating it through subsequent feedings at Reply 43 at http://www.pizzamaking.com/forum/index.php/topic,12824.msg128775.html#msg128775 and continuing, with some discussion of related matters in between, to Reply 76 at http://www.pizzamaking.com/forum/index.php/topic,12824.msg131448.html#msg131448. I believe during the span of those posts that Chau used commercially leavened starters that were held both in the refrigerator and at room temperature. Chau can correct me if I misinterpreted what he said but I believe that he concluded at least two things: that commercially leavened starters did not produce a tangy or sourdough flavor in the finished crust, and it was highly questionable that a commercially leavened starter could be perpetuated for long before being overtaken by wild yeast. In fact, in Reply 76 referenced above, Chau said that the cake yeast leavened starter that was fermented at room temperature was so acidic and masked all other flavors that he decided to end the experiment.

It has always been my belief and contention that it is not possible to perpetuate a starter based entirely on commercial yeast. Rather, I believe that such a starter is eventually taken over by wild yeast.

FWIW, this is what I believe happens when a commercial yeast is used to form a starter that is subjected to future feedings of water and flour, but with no further additions of more commercial yeast.

Once flour, water and commercial yeast (including cake yeast) are combined, there is an initial aerobic phase during which the yeast uses the available oxygen in the dough for reproduction purposes. The oxygen is a prerequisite of cell reproduction. The aerobic phase is followed by an anaerobic phase during which the starter dough ferments (as I understand it, there can also be some further reproduction of the yeast during fermentation, at least in the early stages). The fermentation of the starter dough takes place in stages. In the first stage, the yeast ferments simple sugars that are naturally present in the flour in very small amounts (0.5%). These simple sugars (glucose and fructose) start the fermentation process during which carbon dioxide and ethyl alcohol are produced. In the following stage, certain complex sugars present in the dough (at 1%) are hydrolyzed to simple sugars (glucose, fructose and maltose) to further feed the yeast. The bulk of the sugars needed to feed the yeast come in a final stage from very complex sugars, comprising mostly starch in the flour, that are converted to simple sugars (glucose) by the action of amylase enzymes (alpha- and beta amylase enzymes) on the damaged starch component of the starch (damages starch occurs during milling and in some cases with poor wheat crops). Many of the above conversions require certain enzymes that are included in the yeast cells themselves.

The rate at which the above actions take place depends on the amount of yeast used to form the starter dough, the hydration of the starter dough, and the temperature at which the starter dough is held, either under refrigeration, at room temperature, or maybe a combination of both protocols. In general, the higher the amount of yeast, the higher the hydration value, and the higher the fermentatation temperature, and all else being equal, the faster the fermentation process.

After the initial preparation of the commercially leavened starter, it can be fed with regular feedings of flour and water. With the introduction of more oxygen into the starter dough as addtional flour and water are mixed in with the initial starter dough, there can be further yeast cell reproduction and further conversion of natural sugars into forms of simple sugars needed to feed the yeast, as discussed above. How long this process can continue will depend mostly on the acid levels in the starter dough. The acids in the starter dough are formed as byproducts of the fermentation process (there are many different acids formed although they are individually in rather small amounts). As it so happens, commercial yeast has a high tolerance to pH, even at extremes, but the pH of the starter dough eventually reaches a stage where the commercial yeast ceases to act. According to the article at theartisan.net website at http://www.theartisan.net/The_Artisan_Yeast_Treatise_Section_Two.htm#Yeast GrowthThat (which also discusses the above matters but in much greater detail), the point at which the commercial yeast ceases to act is a pH value of 2 or a pH value of 8. It is perhaps at these values where wild yeast, which can tolerate a wider range of pH values than commercial yeast, can step in and, eventually, take over the commercially leavened starter dough. When this happens will depend on the starting amount of commercial yeast, its hydration value (including when fed regular feedings), the number and timing of feedings, and the fermentation protocol and temperatures. As I understand it, the wild yeast and possibly the bacteria use the dead commercial yeast cells as nutrients. Also, what you end up with as a starter will be governed by the species of wild yeast. It might be a great starter but, then again, it might not.

Peter
« Last Edit: December 08, 2013, 02:29:41 PM by Pete-zza »

Offline arspistorica

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Re: Compressed Yeast to make a Starter?
« Reply #3 on: December 09, 2013, 03:11:56 AM »
Hi,

I was wondering whether you could make a starter out of fresh compressed yeast and keep it alive forever as you can with other starters? The Deli up the road changed hands and has now got fresh compressed yeast available.

Cheers
Warren

No, for a variety of reasons.  Industrial yeast strains can only be grown under diploidy or aneuploidy conditions, resulting in cells that sporulate poorly; have a lower rate of mutation, and hence adaptive fitness, than haploid cells; and, especially under aneuploidy circumstances, experience "chromosomal instability," wherein major transmission errors occur from parent to daughter cells.  Industrial yeast strains are selectively bred for very particular outcomes, with baker's strains chosen for their ability to consume sugars completely and quickly while consequently generating as much carbon-dioxide as possible.  These strains should be seen as "inbred," and are produced for one-off fermentative events (preferments included).

What this effectively means for bakers is there's only so many doublings or generations you can get out of the initial inoculation of yeast.
« Last Edit: December 09, 2013, 01:25:31 PM by arspistorica »
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Offline ThePieman

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Re: Compressed Yeast to make a Starter?
« Reply #4 on: December 11, 2013, 12:57:49 PM »
...SNIP...

What this effectively means for bakers is there's only so many doublings or generations you can get out of the initial inoculation of yeast.

That certainly goes against what bakers have been doing for centuries when using a "mother dough" or "old dough" for levening. I think the big picture is that at an early stage of sourdough culturing, the bakers yeast will provide some initial leavening. As the acid-producing bacteria begin to prolferate and the PH of the culture lessens, the "baker's yeast" will be killed off, leaving the wild strains intact. 

Online Pete-zza

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Re: Compressed Yeast to make a Starter?
« Reply #5 on: December 11, 2013, 01:33:42 PM »
That certainly goes against what bakers have been doing for centuries when using a "mother dough" or "old dough" for levening.
ThePieman,

As noted in the last paragraph of Reply 19 at http://www.pizzamaking.com/forum/index.php/topic,9395.msg81477/topicseen.html#msg81477, according to Prof. Calvel there are some generational limits and penalties to the use of the old dough method.

Peter

Offline ThePieman

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Re: Compressed Yeast to make a Starter?
« Reply #6 on: December 13, 2013, 12:45:10 PM »
ThePieman,

As noted in the last paragraph of Reply 19 at http://www.pizzamaking.com/forum/index.php/topic,9395.msg81477/topicseen.html#msg81477, according to Prof. Calvel there are some generational limits and penalties to the use of the old dough method.

Peter

Indeed, Pete. The reply that I replied to implies that baker's yeast is only good for a few replications. That is not true. In the context of the original question, can baker's yeast be used to make a starter, the answer is an absolute yes. However, as I stated above, the baker's yeast only has a finite life within the culture, as the acid-producing bacteria proliferate to a certain amount. Then, the baker's yeast will begin to die off, leaving behind the wild yeasts.

An advantage of making a starter with baking yeast is that the "starter" will be available almost immediately as a leaven. In a few days, the starter will also be soured to the point where it will add a sour flavor to your baked goods, though the primary leavening will still be coming form the baker's yeast.

Offline arspistorica

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Re: Compressed Yeast to make a Starter?
« Reply #7 on: December 14, 2013, 11:52:02 AM »
Indeed, Pete. The reply that I replied to implies that baker's yeast is only good for a few replications. That is not true. In the context of the original question, can baker's yeast be used to make a starter, the answer is an absolute yes. However, as I stated above, the baker's yeast only has a finite life within the culture, as the acid-producing bacteria proliferate to a certain amount. Then, the baker's yeast will begin to die off, leaving behind the wild yeasts.

An advantage of making a starter with baking yeast is that the "starter" will be available almost immediately as a leaven. In a few days, the starter will also be soured to the point where it will add a sour flavor to your baked goods, though the primary leavening will still be coming form the baker's yeast.

Your point is a semantic one and somewhat beside the point.  OP was asking if a culture could be established and indefinitely maintained using baker's yeast.  The answer to this question is clearly no, for the reasons already given. (For the record, there is a theoretical limit to the number of generations industrial yeast strains can achieve.) Using baker's yeast or any random carbon source (like fruit) to establish a sourdough culture only adds unnecessary steps and total time it takes for proper establishment.  E.g., a fully-viable, stable type-I sourdough culture can be realised in 5 to 7 refreshments using optimised processing conditions, which can be realised in as little as 3 days.  All starters undergo a three-phase evolution, which can be cut short to two using optimal conditions (mainly through substrate and temperature), and will always require a minimum of 5 to 7 refreshments.  Using non-adapted culture sources (like baker's yeast or fruit) does nothing more than add extra refreshment steps at the beginning of the process until that source's cell population has been exhausted, at which point the normal three-phase evolution to create a sourdough starter begins.  This means the minimum number of refreshments to achieve a culture goes up, usually by several refreshments in the case of fruit and even more in the case of baker's yeast, with the latter having more "growing pains" (unreliable leavening properties and dough outcomes) during the transitional phase.

For the record, the "old dough" method, when used with baker's yeast, has mostly been practiced with the introduction of fresh (re: viable) yeast to the final dough on a daily basis, whereas "mother" doughs, historically speaking, refer almost exclusively to purely sourdough-based cultures (this would be la mère in the French tradition, the dough before le levain-chef).
« Last Edit: December 14, 2013, 12:00:41 PM by arspistorica »
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Offline ThePieman

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Re: Compressed Yeast to make a Starter?
« Reply #8 on: December 14, 2013, 02:25:09 PM »
Your point is a semantic one and somewhat beside the point.  OP was asking if a culture could be established and indefinitely maintained using baker's yeast.  The answer to this question is clearly no, for the reasons already given. (For the record, there is a theoretical limit to the number of generations industrial yeast strains can achieve.) Using baker's yeast or any random carbon source (like fruit) to establish a sourdough culture only adds unnecessary steps and total time it takes for proper establishment.  E.g., a fully-viable, stable type-I sourdough culture can be realised in 5 to 7 refreshments using optimised processing conditions, which can be realised in as little as 3 days.  All starters undergo a three-phase evolution, which can be cut short to two using optimal conditions (mainly through substrate and temperature), and will always require a minimum of 5 to 7 refreshments.  Using non-adapted culture sources (like baker's yeast or fruit) does nothing more than add extra refreshment steps at the beginning of the process until that source's cell population has been exhausted, at which point the normal three-phase evolution to create a sourdough starter begins.  This means the minimum number of refreshments to achieve a culture goes up, usually by several refreshments in the case of fruit and even more in the case of baker's yeast, with the latter having more "growing pains" (unreliable leavening properties and dough outcomes) during the transitional phase.

For the record, the "old dough" method, when used with baker's yeast, has mostly been practiced with the introduction of fresh (re: viable) yeast to the final dough on a daily basis, whereas "mother" doughs, historically speaking, refer almost exclusively to purely sourdough-based cultures (this would be la mère in the French tradition, the dough before le levain-chef).

arspistorica, you're preaching to the choir. I've been doing this for years and years. My go to starter is a 70-year-old starter which has been maintained through generations and passed on. I've researched this until I was blue in the face. I certainly do not know everything, however, I do understand what I am speaking of.

I believe my explanation was quite sufficient to the reader that baker's yeast in a "starter" would die off once the acid-producing bacteria began to proliferate and reached a certain level, leaving behind the wild yeasts. The reason that the baker's yeast dies off in a starter, has absolutely nothing to do with the finite replication abilities of the baker's yeast in it's reproductive cycle. It has to do with the face that, in a starter,  baker's yeast simply cannot be maintained in the acidic environment of the starter.

Offline arspistorica

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Re: Compressed Yeast to make a Starter?
« Reply #9 on: December 14, 2013, 02:52:40 PM »
arspistorica, you're preaching to the choir. I've been doing this for years and years. My go to starter is a 70-year-old starter which has been maintained through generations and passed on. I've researched this until I was blue in the face. I certainly do not know everything, however, I do understand what I am speaking of.

I believe my explanation was quite sufficient to the reader that baker's yeast in a "starter" would die off once the acid-producing bacteria began to proliferate and reached a certain level, leaving behind the wild yeasts. The reason that the baker's yeast dies off in a starter, has absolutely nothing to do with the finite replication abilities of the baker's yeast in it's reproductive cycle. It has to do with the face that, in a starter,  baker's yeast simply cannot be maintained in the acidic environment of the starter.

Without wanting to trek too far down this path, as I do not like polemics, it should be noted Saccharomyces cerevisiae is the principal yeast in human food fermentations, and, as such, whenever industrial strains are used near--or, worse, in--sourdough starters, there's a very high probability of contamination by wild mutagens of the initial commercial strain due to mutations from genomic instability.  Wild strains of S. cerevisiae are more highly tolerant of acidified conditions than their commercial counterparts and can remain a permanent member of a stable sourdough culture.
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Offline ThePieman

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Re: Compressed Yeast to make a Starter?
« Reply #10 on: December 15, 2013, 04:32:09 PM »
Without wanting to trek too far down this path, as I do not like polemics, it should be noted Saccharomyces cerevisiae is the principal yeast in human food fermentations, and, as such, whenever industrial strains are used near--or, worse, in--sourdough starters, there's a very high probability of contamination by wild mutagens of the initial commercial strain due to mutations from genomic instability.  Wild strains of S. cerevisiae are more highly tolerant of acidified conditions than their commercial counterparts and can remain a permanent member of a stable sourdough culture.

There are countless books written by old-school Italian bakers who list starters containing baker's yeasts in the initial formula. Remember son, this is food, NOT a science experiment.

Happy eating.  :chef:

Offline arspistorica

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Re: Compressed Yeast to make a Starter?
« Reply #11 on: December 15, 2013, 07:20:47 PM »
There are countless books written by old-school Italian bakers who list starters containing baker's yeasts in the initial formula. Remember son, this is food, NOT a science experiment.

Happy eating.  :chef:

It's funny how science is only relevant when it happens to be about what one knows; once the subject matter wades into unknown territory, it is conveniently laid to the wayside.  Not wanting to stir the pots too much, just because something is written does not make it true.  This is one of the reasons I have begun my project exploring the science of baking; where its findings taper off, I let the artistic, the cultural, the traditional, and even the personal take over.  All of these considerations are not mutually exclusive.  Although I professionally trained under the first generation of molecular gastronomists, I kick it old school.  Always have, always will.

I, for one, am not content reading statements in books like, "Wet starters favour lactic fermentation and dry starters acetic." Or "The mass effect helps speed fermentation."  Yes, but, why and how?  Since embarking on this journey of mine I have answered these and many other topics I have yet to see thoroughly explained by traditional baking and pizza literature, even that which is highly technical.
« Last Edit: December 15, 2013, 08:15:42 PM by arspistorica »
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Offline Wazza McG

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Re: Compressed Yeast to make a Starter?
« Reply #12 on: December 21, 2013, 08:09:45 AM »
So compressed yeast will not survive in the acid environment and wild yeast will eventually take over - does that mean the acids created by the compressed yeast enhance a combined different flavor with the wild yeast?

Would there be good enzymes in the compressed yeast or only in the wild yeast?

I read all of Chau's thread and others and was totally absorbed.  Thanks for the head up.
Fair Dinkum - you want more Pizza!  Crikey ! I've run out out them prawny thingymebobs again!

Offline arspistorica

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Re: Compressed Yeast to make a Starter?
« Reply #13 on: December 24, 2013, 07:01:59 PM »
So compressed yeast will not survive in the acid environment and wild yeast will eventually take over - does that mean the acids created by the compressed yeast enhance a combined different flavor with the wild yeast?

Would there be good enzymes in the compressed yeast or only in the wild yeast?

I read all of Chau's thread and others and was totally absorbed.  Thanks for the head up.

First, enzymatic activity likely does not play as large a role in explaining the differences between industrial and so-called "wild" yeast.  Second, you're right, industrial yeast does not cope as well in acidified conditions, but it's likely lowered pH conditions in a continuously-maintained dough began with commercial yeast is not the reason for dwindling yeast cell numbers. (The cause is likely for the reasons stated above in previous posts.) Yeast, either wild or industrial, both produce minute amounts of organic acids, most of which do not end up in the final, baked product, as they are thermally-degraded due to their naturally-low levels of occurrence.  Doughs started with industrial yeast tend to have a final pH of around 5.2.

As to the question of flavour, that's a more complex answer, as aromatic volatiles and their precursors are determined by an interaction between substrate, fermentation temperature, amount of enzymatic activity in a dough, and type of leavening culture used.  For all intensive purposes, industrial yeast can be simplified to two groups of flavour compounds directly due to their metabolic action, alcohols and fatty-acid esters, while others depend upon their indirect effect in doughs (such as amylolytic activity and so on; there are other compounds directly attributable to yeast fermentation, but most exist at thresholds below human perception in baked, final products).  It is partly for this reason I do not advocate the use of long, cold rises when solely using industrial yeast, as is common on this forum, because it produces an end product with significantly less (and, to my mind, more undesirable) flavour compounds, mostly isolated to the alcohol group.

Flavour in sourdough fermentations is a much more involved answer, with too many variables to get into here.  The short answer is, yes, sourdough produces a wider range of, both, more "desirable" and a greater quantity of flavour compounds.
« Last Edit: December 24, 2013, 07:04:17 PM by arspistorica »
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