Biomedical Engineering Reference
In-Depth Information
Chapter 4
Technology of Sourdough Fermentation
and Sourdough Applications
Aldo Corsetti
4.1
De fi nition of Sourdough
Sourdough technology is widely used in bread making and cake production as it
confers distinctive characteristics, high sensory properties and shelf life to the
resulting products (Table
1
). Sourdough is “a mixture of wheat and/or rye flour
and water, possibly with added salt, fermented by spontaneous (from flour and
environment) lactic acid bacteria and yeasts which determine its acidifying and
leavening capability. These activities are obtained and optimized through con-
secutive refreshments (or re-buildings, replenishments, backslopping)” (
3-
5
) .
The term refreshment deals with the technique by which a dough made of flour,
water and possibly other ingredients ferments spontaneously for a certain time
(possibly at a defined temperature) and it is subsequently added as an inoculum to
start the fermentation of a new mixture of flour and water (and possibly other
ingredients).
When applied for a defined interval of time such a process provides a sourdough
with constant and repeatable leavening and acidifying performances reliant on the
growth of lactic acid bacteria and yeasts that are well adapted to the environment.
After the preparation of the sourdough, the refreshment technique is aimed at main-
taining the metabolic activity of the microbial communities at all times (
6
) .
When the sourdough is added to a mixture of water and flour to start consecutive
propagations (refreshments) to obtain the final mass or full sour to be used as the
leavening agent, it can be designated the “mother sponge” (
2,
4
) . Generally, a sour-
dough contains a variable number of lactic acid bacteria and yeasts, ranging from
10
7
to 10
9
cfu/g and 10
5
to 10
7
cfu/g, respectively, with a ratio of about 100:1 (
7
) .
