Hello Fellow Bread bakers:
I know that the readers of this digest are very interested in the science
of bread baking, so I thought I would let you know about a fantastic
seminar I attended at the Bread Bakers Guild of America in the Retail
Bakers Association annual convention this past weekend. The Guild organized
six of the top sourdough experts in the world--a sort of sourdough dream
team--to speak about the biochemistry of sourdough and to give practical
baking advice about sourdough baking in "Sourdough: The Science, and Its
Practical Application in Your Bakery".
I learned a tremendous amount, and thought I would pass on (see below) a
few of the really juicy but scattered tidbits that I learned at the seminar
and afterward interviewing the speakers. For those interested in the whole
pie, a DVD was made of the talks, and a CD was made of the power point
presentations, and both will be available soon from the Bread Bakers Guild
of America. Contact Gina at gina@bbga.org for more information.
All the best,
Maggie Glezer
PS: Hi back to Michael!
From Walter Hammes, professor of general food technology and microbiology
at Hohenheim University in Stuttgart, Germany, who informed me that he has
been studying sourdough microbiology for 27 years:
During slow, cool yeast fermentations, the extra flavor gained is not from
the enzymatic release of sugar in the damaged starch granules, which
happens relatively quickly in the dough, but from a multitude of other
compounds called flavor precursors released by the activity of yeast and
bacteria. The flavor precursors become flavors during the browning reaction
of baking in the crust of the bread.
Some sourdough bacteria are homofermenting, meaning they produce only
lactic acid, while others are heterofermenting, meaning they produce
primarily lactic and acetic acid or lactic acid and ethanol, depending on
the ambient temperature and other conditions. What I found particularly
fascinating was that the same amount of lactic acid is always produced,
while the acetic acid varies.
Warmer temperatures and wetter doughs favor the development of the milder
lactic acid (think yogurt) while cooler temperatures and stiffer doughs
favor the development of the much sharper and more aromatic acetic acid
(think vinegar).
The balance of lactic acid and acetic acid determines part of the flavor
profile of sourdough breads. This balance is called the FQ, for
fermentative quotient.
Sourdough fermentations have numerous benefits including increasing the
bioavailability of minerals in the flour, removal of toxins and mycotoxins.
Sourdough breads also have a much improved glycemic index, and do not cause
the blood sugar to spike and drop as dramatically as ordinary yeasted
breads. The reason is as yet unclear.
The origin of many sourdough bacteria remains a mystery. Some of the
bacteria thrive in nature in extremely odd places, like the teeth of
children in South America, the human digestive track, or duck's throats.
Prof. Hammes cannot answer how they find their way into starters, but once
there, they become extremely dominant and stable.
From Hubert Chiron, master baker (a real master baker) from the National
School for Milling and Cereal Industries in Nantes, France:
French customers admire what Professor Raymond Calvel calls a "wild crumb"
meaning a vastly irregular crumb structure with abundant huge holes. The
holes develop as a result of air bubbles in the dough coalescing, and
forming super bubbles. To achieve this gorgeous _alveolage_, or crumb, he
recommends moderate mixing (which is never a problem at home), to prevent
the formation of too many air bubbles (nucleation); a long thorough
fermentation (_pointage_), a good rest after rounding the dough, skilled
shaping, and a relatively short proof (_apret_).