Food Biochemistry and Food Processing

626 Part VI: Fermented Foods

every 8 hours. This is called “rebuilding.” Such es-
tablished cultures are referred to as Type I sour-
doughs (Type I process), and a three-stage fermenta-
tion procedure is considered necessary to obtain an
optimal sourdough. Each step is defined by specific
dough yield, temperature, and incubation time.
Dough yield is defined as:

A high dough yield implies that a relatively large
amount of water is used to make the dough; such a
dough would conform with certain requirements in
industrial production when there is a need to pump
the dough.
The lactobacilli and yeasts in Table 27.2 are all
common in sourdoughs; however, the composition
of starter cultures for Type I processes have been
continuously stably maintained for many years, and
may be compared to certain mixed cultures in dairy
technology. The LAB and yeasts in such cultures
will be particularly well adjusted and adapted for the
conditions in sourdoughs. In Germany, established
natural sourdough starter cultures with a stable com-
position ofLb. sanfranciscensisandCandida milleri
have been propagated for decades; they are marketed
as “Reinzuchtsauerteig.” When the sourdough pro-
cess has been started through a one-stage or a three-
stage procedure, a part of the optimized dough is
withdrawn to start up the sourdough production for
the next day. These sourdoughs are mentioned in dif-
ferent languages as Anstellgut (German), mother
sponge (English), chef (French), masa madre (Span-
ish), madre (Italian).
Sourdoughs in Type II processes are used mainly
for enhancing the flavor and taste of the regular bread.
Addition of baker’s yeast is required for efficient
leavening. Type I sourdoughs are good alternatives as

(Flour + Water) by weight

Flour by weight

=×1000 Dough yield

starters for the production of Type II sourdoughs. At

the start of a production period, industrially large

quantities of Type II sourdoughs may be stocked for

portion-wise use over time.

Sourdoughs for Type III processes are dried sour-

dough preparations.

Defined cultures have also been marketed; how-

ever, the suitability of Type I and Type II cultures

appears to outcompete the alternatives offered. In

addition to baker’s yeast the collection of defined

cultures comprise at least pure cultures of Lb. brevis

(heterofermentative) and Lb. delbrueckiiand Lb.

plantarum(homofermentative). The homofermenta-

tive cultures produce mainly lactic acid under anaer-

obic conditions, whereas the heterofermentative cul-

tures will also produce acetic acid or ethanol and

carbon dioxide. By controlling, if possible, the con-

tributions from these different cultures, the relative

amounts of acetic and lactic acids may be regulated.

This important relationship

is called the fermentation quotient (FQ).

Relatively mild acidity will have an FQ about 4–

9, whereas a more strongly flavored rye bread, as

produced in Germany, requires a much lower FQ,

for example, 1.5–4.0 (Spicher 1983, Gobbetti and

Corsetti 1997, Hammes and Gänzle 1998, Martinez-

Anaya 2003, Stolz 2003).

SOURDOUGHPROCESSES

Several more or less traditional sourdough processes

are practiced on a large scale in present-day bakery

industry. One line comprises processes designed for

baking with rye flour. They may be the Type I pro-

cesses mentioned above. The Berliner short-sour

Lactic acid (Mole)

Acetic acid (Mole)

Table 27.2.Common Representatives of Lactic Acid Bacteria and Yeasts Isolated from Mature

Sourdoughs

Heterofermentative Homofermentative

Lactic acid bacteria Lactobacillus sanfranciscencis(formerly Lb. Lb. plantarum
sanfrancisco, Lb. brevissubsp. lindneri) Lb. brevis, Lb. delbrueckii
Lb. fructivorans, Lb. fermentum, Lb. pontis, Lb.
sakei (formerly Lb. bavaricus, Lb. reuteri)
Yeasts Candida milleri, C. krusei, Saccharomyces cerevisiae,
S. exiguus Torulopsis holmii, T. candida