Yeast/Bacteria Source

I know a lot of people have different opinions about starting their sourdough cultures. Some people use fruit to start off while others use just flour and water. Others say it comes from your hands (???). A lot of people claim that even if you use fruit the yeast/bacteria that eventually populate your sourdough come from the flour anyway because the yeast/bacteria from the flour are better suited to it.

But does anyone know how true this is? Has this been tested before? I'm just curious. It would be fun to try to run a lab experiment or something!


16 comments


Go for it, Edmund! Once and for all, let's dispel some myths.


Hello,

About the natural leaven (I prefer that appellation to sourdough which can be just a fermented dough with yeast), you can start it as you want.
The advantage of using fruits is to boost the process. The fruits' skin (better with organic fruits) is full of wild yeasts and bacteria. Moreover, the fruits contain sugars which help too.
But, when you refresh your leaven, you use only flour and water. So, after a while, the population (bacterias and yeasts) of your leaven will be much more influenced by your flour, your hands (eventually) and your bakehouse rather than the fruits you used at the origin, even if it as a certain influence.
An other thing is very important is the method you use for your refreshing. The temperature, the proofing time of your "chef" ("mother"), the oxygenation, the hydration, ... are very important. They give different type of leaven, of populations and, of course, of taste and flavours.
For exemple, when I was in Australia, I developped a leaven to make croissants (without baker's yeast) which had a taste of yoghurt. And there wasn't any trace of milk in it... 8-) I think Graham tasted the croissants.

 -- 

Éric

 

[quote=gul_dekar]I know a lot of people have different opinions about starting their sourdough cultures. Some people use fruit to start off while others use just flour and water. Others say it comes from your hands (???). A lot of people claim that even if you use fruit the yeast/bacteria that eventually populate your sourdough come from the flour anyway because the yeast/bacteria from the flour are better suited to it.

But does anyone know how true this is? Has this been tested before? I'm just curious. It would be fun to try to run a lab experiment or something![/quote]

G'day Edmund,

I have use fruits as an initial source of fermentation. In fact I did that just recently with an Australian native fruit called Lilly Pilly. I've been wanting to do that for a number of years but never got to it. In fact I picked the fruit from a local common with my 3 year old daughter. I took it to work the next day on the train and left it there. So it nearly didn't happen this time either!





































(I hope I'm allowed to attach this picture)
 
You can see some images in my [url=http://sourdough.com.au/?q=gallery&g2_itemId=12230]gallery[/url]. I mainly use this technique with aromatic fruit such as quince. Or in the lilly pilly case, curiosity. But in my experience after some time cycling the sourdough the original fruit influence dissipates and the sourdough seems to revert to a sourdough more akin to one started with a flour substrate. I guess you'd be the right bloke to test any relevant hypotheses. 

I'm going to bake my next lilly pilly bread today as the sourdough has been cycled again. I'll post the pictures later but it'll be interesting to examine the flavour and aroma change from the first ones. The first lilly pilly bread had an unusual aroma and flavour, pleasant but not run of the mill, it had a noticable peppery backnote among other things I just can't describe.   

  

[quote=EricD]An other thing is very important is the method you use for your refreshing. The temperature, the proofing time of your "chef" ("mother"), the oxygenation, the hydration, ... are very important. They give different type of leaven, of populations and, of course, of taste and flavours.
[/quote]

Eric I have to agree with you, the most influential parameters on sourdough flora, hence bread character - which includes, flavour, aroma, and to a lesser extent, loaf appearance are;

* hydration
* temperature range
* fermentation time

Of course this not only applies to the sourdough but also to the bread dough.

 

[quote=Danubian][quote=gul_dekar]...... yeast/bacteria that eventually populate your sourdough come from the flour anyway because the yeast/bacteria from the flour are better suited to it. [/quote]

I'm going to bake my next lilly pilly bread today as the sourdough has been cycled again. I'll post the pictures later but it'll be interesting to examine the flavour and aroma change from the first ones. The first lilly pilly bread had an unusual aroma and flavour, pleasant but not run of the mill, it had a noticable peppery backnote among other things I just can't describe.[/quote]

Ok, I baked the bread and found the flavour and aroma was more akin to the sourdough I've been cultivating for a long period in flour. It wasn't entirely the same but had similarities. It has a wonderful sweet honey aroma. The peppery aroma has been almost extinguished.

Interestingly enough the only variation was the sourdough cycled one further time, everything else was the same as is humanly possible in a bakery.
This shows that, apparently, even if the origin of the leaven influences it, the flour tend to influence mainly the leaven on a long time.

So, there is a way which is interesting to explore : it is to refresh a leaven regularly
with a fruit extract to bring some special bacterial strains which are not from the flour or the bakehouse environnement in order to get special flavours in the leaven and, obviously, in the bread.
In fact, in this case, this is working with a flavoured leaven.

 -- 

Éric

 

Eric,

Here are a few links to posts where we've mentioned the influence of fruit and the need to replenish the 'stock' to continue or boost the fruit influence.
[url=http://sourdough.com.au/?q=forum/topic/1093#comment-8382]Here[/url] and then  [url=http://sourdough.com.au/?q=forum/topic/1093#comment-8463]here[/url]

I guess you really would be correct to say these are "....... flavoured leaven[s]".

Here's another link you may find interesting.

[url=http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2075033#fn1]Influence of Geographical Origin and Flour Type on Diversity of Lactic Acid Bacteria in Traditional Belgian Sourdoughs[/url]

Cool! Will definitely keep the article in mind. Maybe I'll try and see if I can find wheat flours from different regions when travelling around in July to see if I can come up with a short experiment later on.

Could you describe the way you start your fruit starter though? Do you soak it in water (I'm looking at the pictures)? I tend to just crush the fruit and let it ferment in its own juices.  

p.s. Hmmm...wouldn't the fruit a make a nice fruit wine as well especially with the nice purple hue? I'm sure people who be intrigued at the very least.



I believe the main function of the fruit is to provide some acidity, and an initial cosmetic fizz
Thank you Danubian for these links.
gul_dekar, if you want to start a leaven with fruits, take some organic fruits like grapes, apples, pears, or whatever could ferment easily producing nice flavours, acidity and gaz.
Do not wash them and make a purée with the whole fruit (including the skin). Keep this in a warm place for several days in order to get the searched for fermentation with this typical slightly bubbleling. Then, you filter this purée to get the fermented juice. So, you use this like water to start your leaven, liquid or stiff, as you wish.

Jacklang (that's funny, Jack Lang is the name of a former minister of culture), I am sorry but the fruit juice is not there mainly to bring some acidity or gaz but some sugar as a booster and, especially, microorganisms to start the leaven (wich is a culture of bacterias and yeasts).

 -- 

Éric

 

Not surprisingly the yeasts and lactobacilli that live on flour are different to the ones that live on fruit. The bugs in sourdough come from the flour rather than the fruit. Introducing bugs from the fruit at best does nothing and at worst competes for nutrients with the stable symbiosis you are trying to encourage.

As I said, there is a minor beneficial effect on pH.

Leave out the fruit. You will get a stable starter quicker.
The wine - fermented liquid - aroma was much like a late harvest wine, something like a Tokaji. It was beautiful. This surprised me a little since lilly pilly fruit isn't overly sweet.

The reason I used water was to make a large enough amount with a single cycle because I wanted to bake a few loaves for family members who expressed interest and agreed to be the taste testers. The reason for a bake test with only one cycle was to keep the process as gererationally close to the fruit ferment as possible to gauge the flora influence before species dilution dissipated the specific flavours and aromas. Of course I was going to continue to cycle this and bake every time to see what changes if any occur with each subsequent generation.

With lilly pilly - a rainforest tree - it was a matter of seeding the fruit, it contains a single pip. Although not strictly necessary I do it anyway since it allows me to break the fruit open to expose the flesh then cover with water and put a plastic film over it to protect it from outside influences such as spore forming moulds. Needless to say my containers were clean although not sterile.

After 7 days I strain the liquid into a bowl and discarded the solids. The liquid was then added to organic stoneground wheatmeal flour with a dough yield (DY) of 200. allowed to ferment for 24hrs; I guess this is technically a generation cycle but I counted it as and introduction phase since the flora was going from a fruit substrate to a flour substrate. I was amazed how active it was, although showed only modest acid formation it was a very efficient gas producer. The next cycle which I counted as the first, was also active doubling in size within 3hours confirming yeast dominance. It was allowed to ferment for 24hrs and introduced into a bread dough. The bread had good volume and an interesting mix of flavours and aromas with a nocticable peppery backnote that lingered. It was not unpleasant but a little surprising.

The next cycle yielded bread of slightly lesser volume with almost no pepper backnote but a lingering honey flavour. The only variable was the additional cycle, every other variable was maintained as much as is humanly possible.

Several family tasters found a noticable difference. Although they liked the second bread they were also taken by the first. They described it as being different to any bread they had tasted before.

There's no question the fruit was the source of the microflora but also provided the necessary nutrients to support maximum flora population growth. There's plenty of evidence that many of the species of yeasts and lactics found in sourdough are also found living with other plants and specifically on plant fruit. Of course species and strains vary from place to place, substrate to substrate but there seems to be some overlap with sourdough flora.


Several scientific papers have been published on this topic.

Kulp and Lorenz in the Handbook of Dough Fermentations p35  (2003) isbn 0824742648 cite Nout and Creemers-Molenaar (1987) "Microbiological properties of some wheatmeal sourdough starters" Chem. Microbiol. Technol. Lenensm 10:162-167 who showed that after 7 weeks and 20 refreshments the stable culture contained only Lb.sanfrancisco and a yeast, even though Lb.sanfrancisco could not be detected at the start and all the other strains of lactobacteria had gone.

Others such as Bocker et al (1990) confirmed this result, even wher cultures were deliberately contaminated.

These yeasts and lactobacilli dont live on fruit - it has the wrong sort of sugars

 [quote=jacklang]

Several scientific papers have been published on this topic.

Kulp and Lorenz in the Handbook of Dough Fermentations p35  (2003) isbn 0824742648 cite Nout and Creemers-Molenaar (1987) "Microbiological properties of some wheatmeal sourdough starters" Chem. Microbiol. Technol. Lenensm 10:162-167 who showed that after 7 weeks and 20 refreshments the stable culture contained only Lb.sanfrancisco and a yeast, even though Lb.sanfrancisco could not be detected at the start and all the other strains of lactobacteria had gone.

Others such as Bocker et al (1990) confirmed this result, even wher cultures were deliberately contaminated.

These yeasts and lactobacilli dont live on fruit - it has the wrong sort of sugars

[/quote]

 I know it's a long time since this thread was active. (there's a time for everything under the sun)

If you note the content of my posts that after only a few hours from when introducing the fermenting fruit liquid into flour/meal dramatic activity was present. If you introduce water into flour/meal it usually takes 72 hours to get dramatic activity. Obviously microflora were in sufficient numbers in the liquid to produce an active fermentation almost immediately.

 Further you will note that I specifically observed a change in the character of the sourdough after each cycle. The end result was a sourdough that was almost identical in character to the sourdough I have cultivated in flour since 1992. It seems my observations are consistent with your cited reference that after several cycles a stable group of microorganisms dominate. That's why my lilly pilly sourdough began to morph into something similar to my other sourdough.

Perhaps you have jumped to the conclusion that " These yeasts and lactobacilli dont live on fruit - it has the wrong sort of sugars". I'm only guessing since I haven't read those papers. However, Spicher et al 1979 have isolated several species of yeasts from sourdoughs;

(Spicher et al., 1979) isolated four sourdough yeasts and listed the sugars metabolised in two ways;

1. Fermentation (fer)
2. Assimilation   (ass)

The table is much as you would find in Bergies Manual with positives (+) and negatives (-) to indicate which, are or are not, metabilised. For the sake of simplicity I've not listed those sugars which are negative but where a sugar is omitted from the list below the specific yeast indicates a negative for that sugar;

 Picia saitoi  

Glucose - fer, ass 
Athanol - ass
  
  • Candida Krusei 
Glucose - fer, ass
Athanol - ass


 Torulopsis holmii (Saccharomyces exiguus)

 Glucose - fer, ass
Galactose - fer, ass
Saccharose - fer, ass
Rafinose - 1/3fer, ass
Athanol - ass


 Saccharomyces cerevisiae 

Glucose - fer, ass
Galactose - fer, ass
Saccharose - fer, ass
Maltose - fer, ass
Rafinose - 1/3fer, ass
Athanol - ass
 
Most - in the case of the paper below 41 fruits analysed contained fructose, glucose, sucrose, and ripe bananas which are the exception up to 16% starch. (I wonder if some maltose would also be present?)   

The Available Carbohydrates of Fruits Determination of glucose, Fructose, Sucrose & Starch BY ELSIE MAY WIDDOWSON AND

ROBERT ALEXANDER McCANCE.

From the Biochemical Department, King's College Hospital, London.

 

www.ncbi.nlm.nih.gov/pmc/articles/PMC1266468/pdf/biochemj01077-0163.pdf

  • Below is a short list of lactics isolated from sourdoughs, there are more but this list will suffice. Bergies Manual of Determinative Bacteriology lists the sugars these lactics metabolise. In every case the species on this list metabolise fructose (excepting L brevis ss(lindneri II),  all metabolise glucose, and 9 of the list metabolise sucrose.

List is from Spicher/Stephan, 1993. Hand Buch Sauertieg, Behr's Verlag GmbH & Co., Hamburg

L casei

L acidophilus

L delbruckii 

  • L farciminis
  • L liechmannii
  • L plantarum
  • L brevis ss (lindneri I)
  • L brevis ss (lindneri II)
  • L bunchneri
  • L fermentum
  • L fructivorans
  • L pastorianus

 

Bergies Manual also lists their native range from silage, human intestines & faeces, dairies & dairy food, meat, wide range of plant tissues including fruit, vegetables including tomatoes, rainforest fruit, etc etc.

I know it's complex but I haven't seen a single thing that would suggest microflora from fruit would not be able to ferment flour/meal sugars. Of course the species mix of lactics & yeasts would change but that doesn't exclude the  fermentation from the fermented fruit liquid. 

It should also be noted that the native range of these lactics is wide indeed from silage, human intestines & faeces, dairies & dairy products, meat, to a host of plant tissues including tomatoes, rainforest fruits, etc.

 

 

 

Its complex.

 Fortunately much of the Handbook is online. http://books.google.co.uk/books?id=eZjIfud742wC&pg=PA140&dq=kulp+and+lorenz&#v=onepage&q&f=false

 

The sourdough LB utilise maltose, which sourdough yeasts do not, so form a symbiotic pair.

 

 

 

 

[quote=jacklang]

Its complex.

 Fortunately much of the Handbook is online. http://books.google.co.uk/books?id=eZjIfud742wC&pg=PA140&dq=kulp+and+lorenz&#v=onepage&q&f=false

 The sourdough LB utilise maltose, which sourdough yeasts do not, so form a symbiotic pair.

 [/quote]

 

I couldn't get the last of the post above in text using the other computer, so I've now added it.

That's no news that sourdough lactics utilise maltose and sourdough yeasts do not utilise maltose excepting S cerevisiae. The lactics in turn utilise yeast  pyruvate. But this doesn't support your assertion that "These yeasts and lactobacilli dont live on fruit - it has the wrong sort of sugars".