Food Biochemistry and Food Processing

27 Bakery and Cereal Products 627

process, the Detmolder one-stage process, and the
Lönner one-stage process are typical for central and
northern Europe. In every case, the process is initiat-
ed by a starter culture, 2–20% (often 9–10%), in a
rye flour–water (close to 50:50 w/w) mixture that is
incubated for 3–24 hours at 20–35°C, depending on
the process. When the resulting sourdough is ready,
bread making starts with an “inoculation” of about
30% sourdough together with rye flour, wheat flour,
baker’s yeast, and salt. The final rye:wheat ratio is
regularly 70:30 w/w. Dough yield is adjusted to sat-
isfy handling (e.g., pumping) and microbial nutri-
tion requirements.
Another line of sourdough processes comprises
those for baking with wheat only. The San Francisco
sourdough process is often mentioned in this connec-
tion; however, Italian wheat sourdough products, for
example, Panettone, Colomba, and Pandoro, are also
very important (Cauvain 1998, Gobbetti and Corsetti
1997, Spicher 1983, Wood 2000).
The starter for San Francisco sourdough is ideally
rebuilt every 8 hours to maintain maximum activity.
However, a mature sponge may be kept refrigerated

for days with acceptable performance. For rebuild-

ing the starter, sponge (40%) is mixed with high-

gluten wheat flour (40%) and water (about 20%) to

ferment at bakery temperature. Final bread making

requires a dough consisting of the ripe sourdough

(9.2%), regular wheat flour (45.7%), water (44.2%),

and salt (0.9%). Proofing for 7 hours follows, during

which the pH decreases from about 5.3 to about 3.9.

A sourdough starter culture for San Francisco

French bread production commonly contains Lb.

sanfranciscensisand Candida holmii.

SELECTION ANDBIOCHEMISTRY OF

MICROORGANISMS INSOURDOUGH

Sourdough breads based on rye or wheat flour or

their mixtures enjoys a remarkable standing in many

societies, either as established, traditional products or

as “innovative” developments for more naturalprod-

ucts and a wider choice of flavors. Well-functioning

and popular sourdough starters that have been main-

tained by simple rebuilding for decades, and the

reestablishment of the “same” stable starter over and

Figure 27.5.The sourdough process.