16. How should I feed my starter for best results?

Continuous culture of the sourdough starter vs the stop start
approach of a home baker is really the big difference between a home
baker and a commercial operation and most home bakers do nothing to
compensate.

The continuous approach in a bakery is exemplified by the starter
culture being doubled every 6-8 hours 365 days of the year (almost).
The home bakers approach is to store the culture and use it
intermittently and so it is worth examining what exactly happens
during this storage process.

The notion of the yeast sporulating on storage etc. is virtually
guaranteed to be wrong for almost all starters. No wild strain of
yeast can sporulate as is frequently stated in books on sourdough,
the FAQ etc. wild yeast most commonly are aneuploid or polyploid and
thus they either do not sporulate or spores have very low viability.
Also no spore would germinate in the 8-12 hour proof given to it in a
bread making regimen.  Both the lactobacilli and yeast are simply
dormant in a stored culture and a certain fraction is continuously
dying as elaborated below.

Both the yeast and lactobacilli are inhibited by the acid produced.
As you store a culture the organisms die - lactobacilli at acid pH
die at the rate of 90% a week when stored at room temperature.  At
cooler temperatures the rate is slower (4 weeks needed at 4 degrees
for 90% mortality). Because the starting culture usually has a large
number of organisms (in the order of 10E7 - 10E9
(10000000-1000000000) per gram of dough in an active culture with the
lactobacilli being higher than the yeast) this very high death rate
is not immediately perceived - the culture is progressively
enfeebled.  At neutral pH the death rate is slower (incidentally this
is the logic why you feed and proof your starter for a very short
time before you return it to the fridge - the proteins in flour
neutralize some of the acid improving survivability and all the
nutrients are not depleted so the culture can grown at a slow rate in
the fridge).

If you do not use a culture continuously but store a culture in the
refrigerator over time only 10%, 1% or less of the culture will be
alive depending on how frequently you use it, what the acidity of the
culture was when you stored it etc.    Simply, feeding the culture
with a equal volume of flour water does not bring the number of
lactobacilli up to the maximum number possible - a two fold dilution
does not really relieve the acid inhibition adequately, and instead
of 10000000 organisms/gram you may have only 1000000 or less.  The
culture is thus never really vibrant - it is simply limping along.

What I do therefore is to do a very large dilution when I pull the
starter out of the fridge say 1/2 to 1 tablespoon to 1/2 cup flour
and a similar amount of water.  This dilution relieves the acid
inhibition and allows the culture to actually divide and grow back
towards the maximum possible.  12 hours later I refeed (doubling the
starter) and repeat this until I have the amount of starter I want
built up.  I always try and adjust this so that there are at least a
few doublings of the starter before I actually incorporate it into a
dough.  I have used starters from Sourdough International exclusively
so cannot comment on the success of this approach with
non-traditional starters (i.e. anything that is fed on something
other than flour and water). This regimen gives a starter with
excellent properties, with respect to souring, leavening etc.   This
is slightly more work than most people usually do but you will be
rewarded by an improvement in flavor, dough characteristics, etc.

-Roland

What is good feeding?  I believe that there are two important things:

First, don't starve the culture.  This means that you should feed the
culture once it shows evidence of strong activity (frothing or rising
depending on the thickness of the starter) and not too long after
that. If you feed too infrequently the cell populations in the
starter will begin to decline due to starvation, etc.

Second, feed the starter by quadrupling (or even quintupling).  This
means that you feed the starter three times it's weight each time you
feed it (i.e., if you have 2 oz of starter, feed it 6 oz of new
food). If you don't have a scale you can do the measurements by
volume, but I think weight is better.  I also think that it is best
to keep the starter at a relatively thick consistency.  Both the
dilution at feeding and the thick consistency are designed to
encourage the presence of certain good lactibacilli. FYI, when one
feeds by such extreme dilution, it is not necessary to maintain a
partiularly large amount.  Starting with a tablespoon of old starter
and mixing this with a quarter cup each of flour/water at each
feeding will leave you with a sufficient amount of starter.

-Sam