Biomedical Engineering Reference
In-Depth Information
Fig. 4.2
Persistence of strains of
Lactobacillus plantarum
(DB200, --
--; 12H1, --
l
--; 2MF8,
--
£
--; G10C3, --D--) and
Lactobacillus sanfranciscensis
(LS6, -
£
-; LS41, -
n
-; LS48, —
♦
—;
LS3, —X—) after sourdough propagation at 30°C for 6 h during ten subsequent days (Adapted
from (
24
) and from (
23
) )
◊
strain composition in type I sourdough propagated by applying different endog-
enous (e.g. type of flour, quantity of water) and exogenous (e.g. temperature/time
of fermentation) parameters should be carefully addressed, both in terms of
identification and typing of dominant and sub-dominant microorganisms (see
Sect.
4.6.1
) as well as to select robust, well-adapting and competitive starter strains
(
23
). The robustness of sourdough lactobacilli varies depending on the species
and on the strains. While the majority of
L. sanfranciscensis
strains showed quite
a low robustness during daily backslopping performed at the laboratory level (
24
) ,
selected strains of
L. plantarum
seemed to share several phenotypic traits that
determined the capacity to outcompete the contaminating lactic acid bacterium
biota (
23
) (Fig.
4.2
).
4.6
Methods to Evaluate the Performance of the Sourdough
Both microbiological and physico-chemical parameters are used to evaluate the
performance of a sourdough. The level of complexity is different and depends on the
purpose of the analyses. The microbiological aspect essentially deals with the assess-
ment of the community of lactic acid bacteria and yeasts, as those microorganisms are
dominant in a good quality sourdough and are generally present at the ratio of approx.
100:1 (
7
). Nevertheless, an array of both phenotypic and genotypic methods is neces-
sary to identify the species/strain composition of the dominant and sub-dominant
microbiota of the sourdough. An overview of those systems is given below.
