Biomedical Engineering Reference
In-Depth Information
Fig. 8.1
Wheat bread prepared without EPS containing sourdough (
a
) compared to bread prepared
with sourdough containing EPS (
b
) (Data from Galle [
10
] )
EPS formation in dough reduced elasticity and strength, demonstrating the
interaction of EPS with the structure-forming components [
10
] . The addition of
sourdough fermented with HoPS-producing strains in wheat and rye dough induced
increased softening and freshness of the crumb and improved specific volume of the
bread (Fig.
8.1
) [
10,
14,
51
]. The baking industry currently employs in situ formed
EPS and their potential as bread improvers is of growing importance. A process was
developed to adapt sourdough microbiota to high sucrose, and to reach a content of
25% dextran [
54
]
.
Dextran interacts with the gluten network and builds structure
resulting in improved dough stability and gas retention. Its high water-binding capac-
ity accounts for the freshness of the baked product. Linear, high molecular weight
dextran has a greater effect on bread volume compared to more branched, high
molecular weight dextran [
51,
54,
55
]. When the same amounts of reuteran, levan, or
dextran were added to wheat dough, dextran exhibited the best effect on viscoelastic
properties of dough and the volume of the final bread [
43
] .
Sucrose metabolism of LAB not only yields EPS but also glucose and fructose.
Glucose supports gas production by yeast and contributes to dough leavening [
10,
25,
56
]. Fructose stimulates mannitol and acetate formation by heterofermentative
LAB. Acetate has antimicrobial properties, but high acetate concentrations nega-
tively influence flavor and bread structure. Beneficial effects on bread volume of
levan and reuteran from
L. sanfranciscensis
and
L. reuteri,
respectively, were miti-
gated by the detrimental effects of acetate (Fig.
8.2
) [
9,
10
] . Different from hetero-
fermentative lactobacilli,
Weissella
spp
.
form only minor amounts of acetate and at
the same time significant amounts of dextran [
15,
47,
48
] . The application of
dextran-containing
Weissella
-sourdoughs provided mildly acidic bread with
improved structure and shelf life. Incorporation of higher amounts of
Weissella
-
sourdough leads to a higher concentration of dextran in the final bread dough with-
out negative impacts on the flavor and texture of the bread [
10,
15
] .
