630 Part VI: Fermented Foods
hydrogen peroxide, carbon dioxide,and ethanol, and
among these, the two organic acids continue to be
the most important contributions for beneficial ef-
fects in fermentations.
Researchers in the field, of course, also consider
and test possibilities that LAB may produce bacteri-
ocins and other antimicrobials. Thus antifungal
compounds from Lb. plantarum 21B have been
identified, for example, phenyl lactic acid and 4-
hydroxyphenyl lactic acid (Lavermicocca et al.
2000). Caproic acid from Lb. sanfranciscensisalso
has some antifungal activity (Corsetti et al. 1998).
A real broad-spectrum antimicrobial from Lb.
reuteriis reuterin (-hydroxypropionic aldehyde),
which comes as a monomer and a cyclic dimer (El-
Ziney et al. 2000). Reutericyclin, which was isolated
from Lb. reuteriLTH2584 after the screening of 65
lactobacilli, is a tetramic acid derivative. Reutericyclin
inhibited Gram-positive bacteria (e.g.,Lactobacillus
spp., Bacillus subtilis, B. cereus, Enterococcus fae-
calis, Staphylococcus aureus,and Listeria innocua),
and it was bactericidal towards B. subtilis, S. aureus,
and Lb. sanfranciscensis. The ability to produce
reutericyclin was stable in sourdough fermentations
over a period of several years. Reutericyclin pro-
duced in sourdough was also active in the dough
(Gänzle et al. 2000; Höltzel et al. 2000; Gänzle and
Vogel 2003).
A few bacteriocins or bacteriocin-like compounds
have also been identified, isolated, and characterized
(Messens and De Vuyst 2002). Bavaricin A from Lb.
sakeiMI401 was selected by screening 335 LAB
strains, including 58 positive strains (Larsen et al.
1993). Bavaricin A (and Bavaricin MN from Lb.
sakeiMN) have the N-terminal consensus motif of
bacteriocin class IIA in common, comprise 41 and
42 amino acids, respectively, and have interesting
sequence homologies and similar hydrophobic re-
gions. Bavaricin A inhibits Listeriastrains and some
other Gram-positive bacteria but not Bacillusor Sta-
phylococcus(Larsen et al. 1993, Kaiser and Mont-
ville 1996). Plantaricin ST31 is produced by Lb.
plantarumST; it contains 20 amino acids, and the
activity spectrum includes several Gram-positive
bacteria but not Listeria(Todorov et al. 1999). A
bacteriocin-like compound, BLIS C57 from Lb. san-
franciscensisC57, was detected after screening 232
Lactobacillusisolates, including 52 strains express-
ing antimicrobial activity. BLIS C57 inhibits Gram-
positive bacteria including bacilli andListeriastrains
(Corsetti et al. 1996).
TRADITIONAL FERMENTED
CEREAL PRODUCTSOnly two cereals, wheat and rye, contain gluten and
are thereby suitable for the production of leavened
bread, but many other food cereals are grown in the
world. On a global basis, a great proportion of cere-
als are consumed as spontaneously fermented prod-
ucts, in particular in Africa, Asia, and Latin Amer-
ica. Most fermented cereals are dominated by lactic
acid bacteria (LAB), and the microflora associated
with the grains, flour, or any other ingredient, to-
gether with contamination from water, food-making
equipment, and the producers themselves, represent
the initial fermentation flora. Malted flour is also an
important source of microorganisms. The changes
that take place during the fermentation are due to
both the metabolism of the microorganisms present
and the activity of enzymes in the cereal, and these
are in turn affected by the great variety of technolo-
gies that are used. The technology may be simple,
involving little more than a mixing of flour with
water and allowing it to ferment, or it may be ex-
tremely complex and involve many steps with ob-
scure roles. Indigenous fermented foods are usually
based upon raw materials that have a sustainable
production in their country of origin and are there-
fore attracting increasing interest from researchers—
both within pure and applied food science and also
in anthropology. These ancient technologies often
have deep roots in the culture of a country, and there
is increasing awareness of the importance of pre-
serving these traditional foods. Many products are
not yet described in the literature, and knowledge of
them is in danger of disappearing. It is therefore
necessary to document the technologies used and to
identify the fermenting organisms and the metabolic
changes that are essential for the characteristics of
the product. It is, however, often difficult to describe
the sensory attributes of a product that is inherently
variable.
In Africa, as much as 77% of the total caloric con-
sumption is provided by cereals, of which rice,
maize, sorghum, and millet are most important. Cer-
eals are also significant sources of protein. Most of
the cereal foods consumed in Africa are traditional
fermented products and are very important both as
weaning foods and as staple foods and beverages for
adults. In Asia, many products are based on rice, and
maize is most widely utilized in Latin America
(FAO 1999).