Experiment to see if Starters can be contaminated

[Jackie Tran]

So I'm really curious to see if a starter can be contaminated or not.  I've read that they can be and that after a short period of ownership, the local yeast flora will take over and all starters of a particular region will be the same.   

Of course I don't personally believe this b/c I have kept up to 5 starters at any one time that seemingly produced different tasting pizza crust and remain unique. 

But to be sure, I devised a rather unscientific and yet simple test to see if starters can be contaminated or not.

I started out by making a commercially yeasted (IDY) starter.  I made a poolish with 50/50 water and AP flour with a bit of IDY.  I then let it become active within 6-8 hours, dumped out half and fed it with 50/50 water/AP flour.   I did this several times until I got an active starter after several hours of feeding.  I tasted the IDY starter at it's peak and it had ZERO flavor.  No hint of any sourness whatsoever.

I then activated my ischia starter and tasted it at it's peak and it had a very distinct citrus lemony taste to it.   I proceeded to dump out half the amount of each starter.   I took 2 tablespoons of the active ischia starter and stirred it into the IDY starter.   I retasted both and the IDY/ischia starter now had a slight "ischia" taste to it.   About 25% of the flavor of the original ischia starter.  I re-fed both starters and let them become active at room temps.  Both are doubling and becoming active at similar rates. 

I will continue to feed both starters side by side with the same regimen and it will be very interesting to see over the next few days and weeks if....

1) The small about of mature ischia in the IDY starter is strong enough to take over the IDY starter
2) If the higher % IDY yeast will outnumber and overpower the ischia thus diluting out the ischia taste.  If this is the case, then the taste of this active IDY/ischia starter should return to a bland/flavorless tasting starter.
3) if both strains of yeast will co-exist in harmony giving me weak tasting ischia starter with the leavening power of IDY. 

I'll keep you all posted of what I find out.   Anyone want to place bets on the outcome?

Chau

[Pete-zza]

Chau,

As a point of clarification, can you tell me the total time frame of your creating the IDY-based starter? Also, how could you tell when the IDY-based starter was at its peak? Was it at its peak expansion?

Peter

[Jackie Tran]

Peter, the IDY starter took approximately 24 hours to make.  I guess I shouldn't have used the term "peak".  What I meant to say was that the starters were active.   I determined that they were active after they pass the float test.   If the starters did not float in water, then more time gas given until they were active before tasting, discarding half, and refeeding.


Chau

[Pete-zza]

Chau,

Here's my amateur's analysis of the situation.

Even if you did not add the Ischia culture to the IDY-based poolish, and you kept feeding it, at some point it would be likely that your local wild yeast, whatever its source(s), would take over the IDY-based poolish. The reason is that the local wild yeast would eventually produce acids in quantities in which the IDY would not be able to survive. I suspect that as the IDY cells died off, they would be consumed by the local wild yeast. I think they call this process "autolysis", or something similar.

Now, with the Ischia culture added to the IDY-based poolish, at some point, there may be a battle between the local wild yeast and the Ischia strain of wild yeast. For a while, until the IDY dies off, the IDY and the local wild yeast and the Ischia wild yeast may co-exist, but once the IDY is gone, that is when the battle between the two wild yeasts is likely to occur. Given enough time, and enough feedings, maybe one of the wild yeast forms will overtake the other. I don't know how long that would take, or how many bread or pizza doughs you would have to make with the two poolish (the IDY with the Ischia and the Ischia alone) in order to make taste comparisons.

If my analysis to this point is correct, you might have saved a step by making a poolish with your local wild yeast and adding some Ischia culture to that poolish. At some point, you would end up making doughs and crust comparisons with the local/Ischia poolish and the Ischia poolish by itself. If both crusts taste like Ischia crusts, then maybe that would be evidence of the ability of the Ischia culture to retain its inherent characteristics and dominance over your local wild yeast.

I look forward to your results with your experiment if only to see if they tell me that I am still an amateur or not.

Peter

[Jackie Tran]

Peter, you make some valid points here.  However, after 24 hours of feeding the IDY poolish/starter I do not believe that a local yeast could have taken over the culture for 2 reasons.   I don't recall the exact initial amount of IDY used to start the poolish but it was enough to make it active after 6 hours.   I don't believe that 6 hours is sufficient time for any dormant yeast in the flour to take off, as it usually takes me around 3-4 days to see any type of activity when making a new starter from just water and flour.  And even at that, I'm not always sure how much of that is bacterial activity vs yeast activity.   After this 6 hour period, I believe the IDY yeast will have propagated to the point of not allowing any local yeast to overtake the culture.   The IDY will have outnumbered and dormant local yeast in the flour. 

Secondly, after feeding for 24 hours and tasting the raw IDY starter/poolish I tasted no hint any sour flavors whatsoever.  The IDY starter was flavorless or just tasted as flour and water would taste minus any yeast.  I know this doesn't necessarily mean that there is an absence of local yeast, but I do find it odd that local yeast wouldn't contribute some flavor profile.   I have made 3 starters in the pass using flour and water for 2 of these starters and raisens for a 3rd starter.  After becoming active around day 3, all 3 starters did develop sour/vinegar type odors.  Now granted I didn't taste these premature starters at the time but I could not perceive them being flavorless as this IDY starter has been.  Also after the starters became active, all 3 had unique and very distinct odors and flavors.  This IDY starter after become active, contribute no odors and no taste that I could perceive outside of wet dough. 

In a separate and future experiment, I could always continue maintaining an IDY starter for a lengthy period of time to see if it ever develops any flavor at all.  If it did, I would then be confident that a local yeast had taken hold. 

Rather than making up breads and pizzas to compare the taste in the end product, I am quite content with just comparing the raw taste of the starters.  I feel that I can more accurately taste the differences in starters in their raw state particularly if I maintain the same feeding schedule.  Now I understand that different starters will have different rates of fermentation, but this should be close enough for an unscientific comparison.  At this point, I'm only curious to know if the IDY starter with ischia will develop stronger or weaker ischia flavors.  This will give me an indication that the ischia is either taking over the IDY starter, is simply being diluted out with each feeding, or maintaining it's small presence (most unlikely of the 3 outcomes).

I am very curious to know the outcome myself.   I am fairly confident that I will be able to distinguish if the IDY starter starts to develop a different flavor from the raw ischia.  If so then I would say that it is possible that a local yeast has taken over.  I think it is likely that the ischia yeast in the IDY starter will get diluted out over time and eventually yeast in the flour used to feed the starters could take over.  If and when they do, I'm also sure they will make their presence known with a unique and different flavor profile as compared to the ischia culture.   

Thank you for your feedback.
Chau

[dellavecchia]

I might have some information to add. I keep two starters at room temp in my kitchen on a shelf. One is the Tartine-style, which was cultivated naturally with local yeast. The next is (was) an Ischia starter. They are both fed every two days with an 80% discard. They started out smelling and tasting very different. Over the course of a few weeks, the Ischia began to mellow, and finally after a few months, they both smell, taste, and act relatively the same way (except for the Tartine being fed bread flour/ww, and the "Ischia" being fed Caputo). This could be due to the amount of discard, or due to the room temp storage. If you have your yeast strains in the fridge, and only take them out to refresh or be used, they may not be exposed to wild yeast long enough to be taken over. Complete guess here.

John

[Pete-zza]

Chau,

I did not mean to suggest that the local wild yeast would take over the IDY-based culture in the short term. Even where I am in Texas where the wild yeast (and maybe the bacteria as well) seem to take hold quite quickly (sometimes as little as a day), depending on the amount of IDY I would be thinking in terms of maybe weeks for the wild yeast to establish a foothold in an IDY-based culture. The question of whether it is possible to make a "permanent" culture using commercial yeast, with regular feedings and without any further additions of commercial yeast, comes up on the forum quite often. Having run a few experiments along those lines some time ago, without any pretense of being scientific about the process, I came to the conclusion that it was not possible. Marc (widespreadpizza) once asked Marco (pizzanapoletana) a similar question, at http://www.pizzamaking.com/forum/index.php/topic,4182.msg34897.html#msg34897. You can see Marco's response in Reply 1. I did a further search this morning and also found another post by Marco, at Reply 8 at http://www.pizzamaking.com/forum/index.php/topic,4125.msg36343/topicseen.html#msg36343, in which Marco discusses the conditions under which wild local yeast might get established in a commercially-leavened dough.

My thinking is that the IDY in a IDY-based culture will outrun any wild yeast for a time, and that action might persist for some while depending on the amount of IDY and the number of feedings (and temperature, etc.), but that eventually the wild local yeast will take over. Then, if Ischia wild yeast is in the culture also, those two wild yeasts battle it out with each other. That is the point where I would like to see what happens.

I hope you don't get stomach aches from eating too much of the cultures  .

Peter

[foolishpoolish]

Interesting experiment Chau. Let us know what happens!

[Jackie Tran]

Good info John.   Apparently starters can get contaminated if the conditions are right.  I would agree that if starters are kept in the fridge and taken out periodically for use and refreshment that it may not be enough time for a local yeast to infiltrate the starter.   I think we have a number of members who have been successful at keeping starters unique for lengthy periods of time.

Peter, thanks for clarifying your earlier post.  I will have a look at these new links you've posted.  

I wanted to quickly update those who are following this.   I fed the starters a few more times after yesterday's post and it "seemed" as if the IDY/ischia starter was losing it's ichia taste.  Before I turned in for the night, I refed both starters and placed them back into the refrigerator as I didn't want them sitting out unsupervised throughout the night.  I did not want there to be any starter hanky panky going on while I was dreaming about making pizza and bread.  

I took the starters out this morning and let them become active at room temps.  I just tasted both again this afternoon and I AM SHOCKED at how similar they taste.  If I had to guestimate, I would say that the IDY/ischia starter has at least 75-80% of the "ischia" taste compared to my active ischia starter.  It appears that the ischia has possibly taken over IDY starter already!  I never would have guess that only a tablespoon full of ischia starter could overtake a half jar of active IDY starter.  I will continue to monitor their progress and also bake up a loaf of bread with the IDY/ischia starter.  

I baked a loaf yesterday with the IDY starter (before I introduced the ischia) and allowed that loaf to ferment really well.  That is I used about 22% IDY starter and did a room temp ferment on a high hydration dough for 9 hours.   The resulting crumb was that of a typical sourdough bread but it had NO sourness to it whatsoever, just like the IDY starter.    I will repeat the bake today using the newly contaminated starter and also allow for it to ferment out very well.  Depending on how sour the bread turns out, I will be able to make a guestimate and confirm how contaminated this IDY starter has become.  

Peter, since some members including myself have been able to keep and maintain distinctly different starters, I wonder how long I can keep an IDY starter going for if I take careful measure to reduce the risks of contamination.  I think I will make up another IDY starter for that experiment.  It should be easy to detect the moment local yeast take a hold of it since I now know the flavorless taste of an IDY starter.  

Chau

[Pete-zza]

Chau,

When I was playing around with natural starters/preferments, I eventually got to the point where I used both a natural starter/preferment and IDY, much as Jeff Varasano and pftaylor combined the two leavening systems, and as Prof. Calvel described for production of French bread in the cool months of the year. I found that the nice crust flavor profile that I got when I used just the natural starter/preferment was lost or significantly lessened when I combined the two leavening systems. I had read of this phenomenon on several occasions so I just assumed that there was merit to the case not to combine the two leavening systems. I just figured that the IDY overwhelmed the wild yeast and suppressed the byproducts of fermentation that might otherwise have come from the actions of the wild yeast. I did not taste the cultures to see if that might have signalled what I could expect in the final crusts. At that time, I did not even know that a culture could be tasted.

Peter

[Jackie Tran]

Peter, I have been using such a technique lately to lessen the flavor of the ischia starter while providing some extra leavening effect through the use of IDY.  I'm not sure about the chemistry that is going on but it sounds good in theory and appears to give me a more desireable product.  It may be that in such a short time frame, both strains of yeast are working side by side until the food resources run out. 

To my taste, it is surprising how the taste of raw starter translates through to the finished product.  It is remarkably similar especially if the dough is allowed to be well fermented into it's later stages. 

As a side experiment this afternoon, I am also reviving my camaldoli starter to taste it side by side with the ischia to make sure that it is absolutely and postively distinct from one another.   B/c I have been using ischia most often I have since gotten rid of my other 3 starters so unfortunately I won't be able to test them as well. 

Chau

[foolishpoolish]

Chau,
I think to benefit *flavourwise* from the ischia (or other starter) in a "hybrid situation" of starter + IDY/baker's yeast, it'd be best to preferment without IDY/baker's yeast and then add the yeast to the final dough. However, acidity from a sourdough preferment used in significant proportions would have an effect on the final dough strength....so it'd be something of a balancing act. Didn't you try adding IDY last minute as an "emergency" step to a naturally "leavened" dough a while back? I forget what your results were....but that might be another approach I suppose!

[shango]

I find that "starters" made with commercial yeast tend to "peter out".  Takes about a week with the fresh yeast I've used. It doesn't surprise me that the  is taking the lead.

I've had my  going at home, at room temp for 3+ years, and actively using it, and solely it, for leavening pizza in the restaurant for the last 7 months. No change, no local strain taking over...

I really don't like commercial yeast, it tastes bad, overly inflates as it leavens and, I suspect, leads to health problems-like Celiacs

[Pete-zza]

Chau,
I think to benefit *flavourwise* from the ischia (or other starter) in a "hybrid situation" of starter + IDY/baker's yeast, it'd be best to preferment without IDY/baker's yeast and then add the yeast to the final dough. However, acidity from a sourdough preferment used in significant proportions would have an effect on the final dough strength....so it'd be something of a balancing act. Didn't you try adding IDY last minute as an "emergency" step to a naturally "leavened" dough a while back? I forget what your results were....but that might be another approach I suppose!

Toby,

You are correct on the "hybrid" method. In The Taste of Bread, p.39, Prof. Calvel says that the commercial yeast should not be in the sourdough mother culture.

Peter

[Jackie Tran]

Chau,
I think to benefit *flavourwise* from the ischia (or other starter) in a "hybrid situation" of starter + IDY/baker's yeast, it'd be best to preferment without IDY/baker's yeast and then add the yeast to the final dough. However, acidity from a sourdough preferment used in significant proportions would have an effect on the final dough strength....so it'd be something of a balancing act. Didn't you try adding IDY last minute as an "emergency" step to a naturally "leavened" dough a while back? I forget what your results were....but that might be another approach I suppose!

Toby,  I did do that recently and posted about it here...
http://www.pizzamaking.com/forum/index.php/topic,12390.0.html

This and first reading about it from Verasano's workflow gave me the idea to utilize this 'hybrid' method.   I have tried several different methods of combining a starter and IDY with similar results.  I have tried adding both to the mix initially and adding the IDY after the the dough has bulked rested with starter.  As I mentioned earlier, I'm not sure the chemistry or dynamics but I have been getting favorable results.  From what I can tell, I have gotten a more mild flavor and more leavening effect than using the ischia starter alone. 

This experiment came about after I created an IDY poolish for the purpose of trying to achieve the look of a tartine bread crumb without the sourness.   I would have to say that my initial impressions of using an IDY poolish is that it does give a different effect than just using IDY alone.   How and why I am not sure. 

UPDATE:  I have been feeding both the IDY/ischia starter and the ischia starter as well as reviving the camaldoli starter all day today.

This afternoon when I came home from lunch, the IDY/ischia starter was very active and tasted quite similar to the active ischia starter.   Almost the same flavor but not quite.   Upon dumping about 75% of it out and refeeding, the ischia taste has mellowed out just a touch throughout the day.  Compared to the ischia starter tonight, I would say that in it's active state, the IDY/ischia starter has a more mellow 'ischia' flavor, about 75% or so compared to the active ischia starter.   It could also be my imagination, but the IDY/ischia starter is definitely showing greater leavening strength compared to the ischia starter.   

I really would like to believe that I have a hybrid starter on my hands but I really don't know at this point. 

Also, I have revived the camaldoli starter and tasted the raw active starter alongside the ischia (something I haven't done before) and I have to say that both have a similar taste.  Although the camaldoli is not as sour as the ischia.  It has a much milder flavor and a hint of sweetness to it as well.  I'm confident at this point that they have remain distinctly seperate starters. 

Chau

[Jackie Tran]

Tonight's bake compared to yesterday's bake.

Yesterday's bake using IDY starter created.  Raw starter had no flavor.  This loaf had 20% starter and allowed to ferment at temps of ~80F for 9hours.   I have made this bread many times before using an ischia starter.  At 7 hours of fermentation I would get a sour tasting bread.  At 9 hours it would be likely very sour.  This loaf had the look and texture of a SD bread but none of the sour taste.  Zero.

Yesterday's bread at reply #591
http://www.pizzamaking.com/forum/index.php/topic,12042.580.html

Today's loaf bake using IDY/ischia hybrid starter.  Raw starter tasted about ~75% of raw ischia starter.   This loaf had 30% starter and allowed to ferment at 80F for only 7 hours total.  Had similar rise and expansion of yesterday's bread but with a slight twang to it.  Not sour but very pleasant for me.  This franken starter I have created is definitely giving me a much more mild ischia flavored bread compared to an ischia bread of this length of fermentation. 

Today's loaf at reply #614
http://www.pizzamaking.com/forum/index.php/topic,12042.600.html

I'll continue to bake with this hybrid starter and keep you guys updated on how it changes over time.  I would love for it to keep giving me these results though. 

Chau

[Pete-zza]

Chau,

As a point of clarification, were the last two loaves made with the IDY/Ischia mix but baked on different days and with different amounts of the mix and different fermentation times?

Peter

[Jackie Tran]

Yes Peter, they were rather different loaves so it was a very loose comparison.   I just wanted to show that the hybrid starter gave the bread some flavor, which was more than the IDY starter loaf and less flavor than an ischia bread loaf.  The first loaf was made with the IDY starter which tasted flavorless in it's active state.  No ischia had been added to it.   It had 20% starter and allowed to ferment for 9 hours.   The crumb & texture was very much reminiscent of a SD bread but without the sourness.   The dough for the 1st loaf was made prior to starting this thread.

The 2nd loaf was made yesterday using 30% of the contaminated IDY starter (IDY/ischia hybrid starter).  It was allowed to ferment for 7 hours.  I would have allowed it to proof longer but it really seemed ready to bake, so I baked it at 7 hours.   It had a very mild SD taste to it.   The raw starter also had a more mild taste compared to an active ischia starter.   

In the past, when I made bread loaves using between 20-30% ischia starter and a fermentation time of 5-7 hours, I recalled a more sour tasting bread.
For my next bake, I plan on making 2 loaves side by side with identical formulas and allowing them to ferment out really well.  I'll use the hybrid starter for one loaf and the ischia starter for 2nd loaf.  I'll compare the taste of the raw active starters to the taste of the finished loaves and report back.

Chau

[Pete-zza]

Chau,

Thanks for clearing that up for me. I thought that you had just two cultures, the IDY/Ischia mix and the Ischia alone. I did not catch that you had the IDY culture alone. If so, that does dovetail with out earlier discussions on trying to keep an IDY-only culture going.

Peter

[Jackie Tran]

Peter, sorry I wasn't more clear on that earlier.  I created an IDY poolish/starter for the purpose of creating a tartine-esque bread crumb without the sourness of a sourdough, thus giving rise to the first loaf.   

After the dough (for loaf 1) was made, came the idea for this experiment and thread and I decided to contaminate the IDY starter with ischia.  The 2nd loaf was made from this contaminated starter after it had been fed 4-5 times.   I initially expected the ischia to be diluted out to the point that it would retain very little ischia taste.  I was surprise to see that it had settled in and setup shop.   After multiple feedings, the hybrid starter maintained it's ischia taste but not to the same strength as an active ischia starter.   I was also surprise to see after the bake that there was some SD flavor but not to the extent that I would have expected for a 7 hour ferment at 80F using 30% starter.  I suspect that eventhough there is presence of ischia in this starter, it has not fully taken over.

I'll bake up 2 loaves next time side by side using the hybrid starter vs an ischia starter so that a better comparison can be made. 

In the future, I would be interested in remaking an IDY starter and seeing how long I can maintain it without it becoming contaminated by local yeast.

Chau