Biomedical Engineering Reference
In-Depth Information
non-conventional flours. They used selected lactic acid bacteria as sourdough
starters to ferment wholemeal wheat, soybean, barley, amaranth, and rye flours.
Sourdough-originated lunasin was identified in their study and the concentration of
lunasin was shown to increase up to two to four times during fermentation.
From a practical standpoint, baked cereal goods are currently manufactured by
highly accelerated processes. Long-term fermentations by sourdough, characterised
by a cocktail of acidifying and proteolytic LAB and yeasts, have been almost totally
replaced by the indiscriminate use of chemical and/or baker's yeast leavening
agents. In these technological circumstances, cereal components (e.g. proteins) are
subjected to very mild or no degradation during manufacture, resulting in less easily
digestible foods compared to traditional and ancient sourdough baked goods [
41
] .
9.2.3
Dietary Fibre
Dietary fibre consists of the plant polysaccharides and lignin that are resistant to
hydrolysis by the digestive enzymes of man. A high consumption of dietary fibre
may lower the risk of cardiovascular disease, diabetes, hypertension, obesity, and
gastrointestinal disorders [
50,
51
]. Cereal foods are an important source of dietary
fibre, and because of their role as a staple food provide an important food group to
increase the currently too low intake of dietary fibre. Sourdough fermentation pro-
vides two main options for enhancing utilisation of fibre-enriched products: (1) It is
important technology in the manufacture of whole grain bread, especially rye bread,
and (2) it may be used to modify fibre-rich cereal ingredients such as bran and germ
for improved technological functionality.
Wholemeal rye and wheat are very good sources of dietary fibre. However, a
high content of fibre poses technological challenges for baking. For whole-grain rye
baking, sourdough fermentation is an essential part of the process [
2
] . Without sour-
dough wholemeal rye or wheat-rye flour mixes are very difficult to process, and
sourdough improves the overall quality and shelf life of whole-grain rye breads.
The rye sourdough process not only improves flavour and texture of rye bread but
enables consumption of wholemeal rye, which is well known for its high nutritional
quality and health-promoting properties.
Bran sourdough (or bran pre-ferment) is a potential means to improve the quality
of high fibre bread [
4,
52-
54
]. The use of bran sourdough improves loaf volume and
crumb softness of high-fibre wheat breads [
4,
52,
55
] and bread with 10-% fermented
bran has been reported to provide the best sensory properties of bread [
53
] . The
impact of fermentation is assumed to be related to control of endogenous microbiota
of bran, endogenous xylanase activity and subsequent solubilisation of arabinoxy-
lans in bran fermentation [
4
]. Enzyme activity and gluten characteristics of dough
containing fermented bran will be modified by the acidity produced during fermen-
tation, and subsequently decreased pH. The fibre content of the bran does not change
significantly in a short fermentation time but can decrease slightly during prolonged
fermentation due to hydrolysis of cell wall structures (Katina, unpublished data).
