Biomedical Engineering Reference
In-Depth Information
hydrolysis of the water-soluble proteins that constitute the outer shell of the starch
granules. As a result, smaller starch granules were released from the matrix and the
pasting properties of sorghum flour were modified. Proteolysis has also been inves-
tigated in the GF product
towga
, a traditional Tanzanian fermented food prepared
by fermentation of either sorghum, maize, cassava, millet or combinations thereof
[
82
]. Both spontaneous and starter-induced fermentations induced the activation of
proteinases and, depending on the fermentation conditions, an increase in the con-
tent of specific amino acids, such as glutamic acid, proline, ornithine, methionine
and lysine.
Overall, the proteolytic events occurring during sourdough fermentation can posi-
tively affect the baking quality of GF flours. Therefore, sourdough fermentation could
replace the use of proteolytic enzymes in GF bread formulations [
30
,
31
] , which would
allow a reduction in the cost of the bread and enable consumers' acceptance issues to
be overcome. However, more studies are needed in order to understand which GF
flours can be positively treated by sourdough fermentation and what degree of prote-
olysis is required in order to enhance their baking performances.
10.5
Proteolysis for Reducing the Toxicity of Wheat Flour
During endoluminal digestion, a family of peptides rich in Pro and Gln are released
from prolamins of wheat and rye. These toxic peptides are responsible for the auto-
immune response in celiac patients [
83,
84
]. During sourdough fermentation of
wheat flour, gliadins are among the most affected proteins, where the extent of
hydrolysis of monomeric gliadins (a -, b -, g -, w -gliadins) is strain-speci fi c [
76,
85
] .
Di Cagno et al. [
76
] showed that selected LAB, possessing proteolytic activities,
could efficiently hydrolyse the 31-43 fragment of the toxic peptide A-gliadin in
wheat sourdough. The same authors further applied the proteolytic LAB for producing
non-toxic sourdough from a mixture of toxic and non-toxic flours, in which the
highly toxic 33-mer peptide was completely hydrolysed [
86
] . Breads produced with
this sourdough showed acceptable quality and when they were fed to celiac indi-
viduals, no alterations to the baseline values of the patients were observed. The
same pool of proteolytic LAB was proven to be efficient for detoxifying rye flour
[
87
] and, when used in association with
L. sanfranciscensis
, for producing non-
toxic wheat sourdough bread of acceptable quality [
88
] . Sourdough fermentation
can also be efficiently applied for eliminating the gluten that can eventually be present
as a contaminant in GF flours [
89
] .
Prolonged sourdough fermentation of wheat and rye using specific LAB may
represent a novel technology for baking good-quality breads that can be consumed
by celiac individuals. Nonetheless, long-term in vivo tests are needed in order to
confirm the suitability of these products for celiac patients. Furthermore, manufac-
turers will have to face the obstacle of gaining the acceptance of consumers towards
GF products containing detoxified wheat and/or rye.
