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Re: Acidity problems

"Mike Avery" <mavery@mail.otherwhen.com>
Sat, 06 Sep 2003 11:18:24 -0600
v103.n039.5
"Gabriel Filloy" <gabriel@prumisa.com> wrote:

>I have been able to create the sourdough bread I wanted.  Using a starter 
>made initially from grapes my bread is great, the only thing I have not 
>been able to control is the acidity of the bread.
>
>Can someone help me on how to control the acidity?

Warning - this is gonna be long, and the bone lazy bakers won't like it.

As with sex, money, and weight, sourdough problems come in two flavors, too 
much and too little.  In several cases, the correct response to "too much" 
is "that's a problem?"

To start with, you should have eaten the grapes.  You would have 
appreciated them more than the sourdough culture.  Grapes, cabbage, and 
other flora and fauna are not needed to start a good culture.  All you need 
is wheat and/or rye flour and water.  Adding the other flora or fauna or 
baker's yeast gives you a quick start, but it's the wrong start. Your 
culture won't mature until the wrong yeasts from these things die off and 
are replaced by yeasts that can do well in a sourdough culture. Yes, you 
can make a good starter using grapes.  But you would have had a good 
starter several weeks sooner if you'd not used the grapes.

The first thing to work on is control of your starter.  It's the foundation 
of all that follows.  You need to have a consistent starter to work with. 
Not lively one time, lethargic another.  While most taste comes from the 
fermenation/rising of the bread and not the starter, having the starter in 
a consistent state helps (is all but essential) to get consistent 
results.  I prefer to have an active starter that is lively and has a 
fruity smell more than a lethargic sour one.  A soured starter is past it's 
prime and won't give you much rise.  The keys here are consistent feeding 
and handling, and if you refrigerate your starter handling it consistently 
after you get it out of the fridge.  I prefer to feed it three times (or 
more), eight hours apart, tripling the volume with each feeding, until the 
starter is very active.  If the starter won't double (or better) in size 
after being fed, how's it supposed to raise your bread?

There are two aspects here, one is how you handle your starter, the other 
is how you handle your dough.  I feel that the goal of handling your 
starter is to get a good crop of healthy, active yeast and bacteria in the 
culture of the right kind.  This prepares the way for the handling of the 
dough.  Most of the taste and character of the bread comes from the 
handling of the dough.  You can blow it if you mishandle the starter, but 
the quality of the bread should come from the dough and it's handling.  All 
of which is to say, you needn't (and shouldn't) use a sour starter to make 
a sour bread.... other things will suffer.

The characteristic sourdough taste comes from lactobacillus bacteria, a 
kind of "friendly" bacteria.  There are two major classes of starters, ones 
with  homofermentative or heterofermentative lactobacillus bacteria 
dominating them.  Homofermentative starters produce primarily lactic acid 
which is mild in taste and which doesn't seem very acidic to the 
taste.  This is preferred by German bakers who need to acidify rye breads 
to get them to come out right and want the improved handling they get from 
sourdough, but whose customers don't like sour breads.  Heterofermentative 
starters produce lots of lactic acid but also produce acetic acid.  These 
starters give more "bite" to the bread.  This is prized for San Francisco 
sourdough bread.

In most stable sourdough cultures, one strain of yeast and one strain of 
bacteria dominate the starter by several orders of magnitude. However, 
since most of us don't have pure cultures, there are other yeast and 
bacteria present.

There is some debate as to whether the hetereofermentative and 
homofermentative lactobacillus are different sub-species of lactobacillus 
that produce the different outcomes, or if it's a matter of 
handling.  Similarly, the same person can practice running and become a 
track star, or can sit in front of the TV and become a couch potato.

Since most of us don't have pure cultures, changing the handling conditions 
can change many cultures from heterofermentative  to homofermentative or 
vice versa.  Is this because the bacteria changed their behavior, or 
because the minority bacteria is now treated better than the majority 
bacteria and took over the culture?  The matter is still being debated, but 
practically spreaking, it really doesn't matter much to the home 
baker.  All you really need to know is that you can often change the 
behavior of your starter by the way you feed it.

Whichever way this works, it helps explain some of the comments about, "my 
starter has changed".  Usually this means you changed how you handle it, 
and it responded.

A thicker starter, around 50 to 60% hydration, will tend to favor 
heterofermentative bacteria.  Thinner starters, around 100% hydration, tend 
to favor homofermentative bacteria.  So, thick = sour, thin = mild.

The kind of flour you use has a tremendous impact on your results. Flours 
higher in ash produce breads with more sour tastes.  Ash is a measure of 
the mineral content of flour.  Ash is usually found in the bran of 
flours.  Since white flours have less bran than whole grain flours, they 
also have less ash.  You can usually see the ash levels of flours on the 
sack.  Many people think of ash as waste, or unwanted.

The use of the term ash is an unfortunate one.  The mineral content of 
flour is (crudely) determined by burning the flour.  (The same is done with 
dog food and other products.)  The carbohydrates, protein and fat are 
burned off.  The water evaporates.  What is left is ash.  It's not that the 
flour (or dog food) has ash in it, it's that it can be burned to ash. The 
amount of ash is an indicator of the mineral content of the flour. Some 
people mix whole wheat and white flour together to get more taste.  (I 
usually mix 1 part of whole wheat to three parts of unbleached all-purpose 
flour by weight.)  More ash = more sour.  Less ash = less sour.

The next thing that helps control acidity is the temperature. 
Heterofermentative bacteria tend to prefer cooler temperatures, while 
homofermentative bacteria prefer warmer ones.  Sourdough starters are 
fairly active from about 50F to about 90F.  On the bottom of the web page 
at <http://www.sourdoughhome.com/risetime.html> I have a chart showing the 
time to double for a common sourdough yeast and lactobacillus bacteria over 
a wide temperature range.  There is some disagreement, but I feel when 
sourdough is refrigerated it largely stops working.  The cooling is not 
instantaneous, so the inside of the bread rises longer than the outside, 
but when you cool something to the 30- something F level, the flour is 
hydrating, but the yeast and bacteria are asleep.  Much beyond 90F, you 
start getting off flavors.  In general, cooler temperatures tend to favor 
the heterofermentative bacteria, higher temperatures tend to favor the 
homofermentative bacteria.  Of course, the temperature also influences the 
length of time of the rise. When things get warmer, up to a point, the 
yeast and bacteria work faster.  When things get cooler, the critters work 
more slowly.  Or, cooler = more sour and slower, warmer = more mild and 
faster. German bakers tend to rise their breads in the mid 90's.  San 
Francisco Sourdough Bread is risen at San Francisco room 
temperatures.  This part is pretty important - if you pull your starter out 
of the fridge and refresh it with pure white flour and keep it at 90F, it 
will take off pretty fast, but the homofermentative bacteria will take over 
the culture, leading to milder bread.  Feeding more bran and using a lower 
temperature will take longer to get the starter reactivated, but this will 
help the heterofermentative bacteria.  This will strongly affect the bread 
you make.

The length of the rise also plays a role in the taste.  Longer rises mean 
more sour taste.  Temperature has it's own influences here, so another way 
to control the speed of the rise is to change the amount of starter 
used.  Using 4 cups of starter will tend to make a milder bread quickly, 
while using 1/2 cup of starter will tend to make a more acidic bread more 
slowly.  Letting the dough rise too long, called overproofing, will tend to 
produce a very fragile dough that will collapse if you slash it or jostle 
it.  Some people like overproofed bread, and they tend to slash the dough 
before they let it rise.

I think those are the key factors.... using this information and keeping 
your goals in mind should help you correct your acidity problems, whether 
you are looking for milder or more acidic bread.

Good luck,
Mike
-- 
Mike Avery
MAvery@mail.otherwhen.com