632 Part VI: Fermented Foods
replacement by cola-type beverages would result in
a serious negative impact on the nutrition of people
in developing countries.
The use of fermented cereals as weaning foods in
developing countries raises several important issues.
Unfermented gruels deteriorate very rapidly in un-
hygienic conditions, especially if refrigeration is not
available. They then represent a significant source of
foodborne infections that annually claim the lives of
millions of young children (Adams 1998). Fermented
malted cereal gruels have been shown on the whole to
contain low numbers of pathogenic organisms since
these are inhibited and killed by the low pH that rap-
idly develops in the product. Fermented cereals are
therefore usually regarded as safer than their unfer-
mented counterparts (Nout and Motarjemi 1997). A
weaning food made from unmalted cereals may be a
cause of malnutrition because its thick viscosity lim-
its the nutritional intake of a small child. Addition of
malted flour decreases the viscosity so that more food
can be ingested. If the fermentation flora includes
yeasts in addition to LAB, a measurable reduction of
carbohydrate will occur due to the production of
CO 2 and other volatile compounds (Muyanja 2001).
Analysis of fermented cereal products therefore shows
that the protein:carbohydrate ratio is improved during
the fermentation, and this obviously has nutritional
benefits.
Milling of cereals into flour is usually done prior
to fermentation, but in some products, for example,
borde (Ethiopia), wet milling is used. This technique
can be used when mechanical grain mills are not
available and if the product is required to be smooth
and without bits of suspended bran. The starch is
also liberated from the grain more thoroughly when
slurried with water and sieved than if it has been
previously dry milled (Abegaz 2002).
A heat treatment step is found at some point in the
production technology of most fermented cereal prod-
ucts and may involve boiling, steaming, or roasting.
The type of heating employed is likely to have an
effect on the flavor of the product, certainly if the
temperature attained is sufficient to promote Mail-
lard reactions. The heat also gelatinizes the starch,
making it more susceptible to amylolytic enzymes,
thus providing greater amounts of fermentable car-
bohydrates. However, at the same time, most of the
natural contaminating (and potentially fermenting)
flora and cereal enzymes are destroyed. Such prod-
ucts are also prone to contamination after the heat
treatment step, and are thereby potentially unsafe
should pathogenic organisms grow during the subse-
quent fermentation. The traditional solution to this is
to use “backslopping,” the addition of some of a pre-
vious batch of the product, and/or the addition of
malted flour. Regular backslopping results in a se-
lection of acid-tolerant organisms and functions as
an empirical starter culture.
Fermentation usually takes place at ambient tem-
peratures, and this may cause seasonal variations in
products due to selection of different microorgan-
isms at different temperatures. The duration of fer-
mentation is largely a matter of personal choice,
based on expected sensory attributes. Heat treatment
after fermentation makes for a safer product, but it
has the disadvantage of change of taste or loss of
volatile flavor and aroma compounds.THEMICROFLORA OFSPONTANEOUSLY
FERMENTEDCEREALSSpontaneously acid-fermented cereal products may
contain a variety of microorganisms, but the flora
in the final product is generally dominated by acid-
tolerant LAB. Yeasts are also invariably present in
large numbers when the fermentation is prolonged.
A typical fermented cereal product contains approx-
imately 10^9 and 10^7 cfu/g of product, of LAB and
yeasts, respectively. However, since yeast cells are
considerably larger than bacteria cells, their meta-
bolic contribution to product characteristics is likely
to be just as important as that of the LAB. The buffer
capacity of cereal slurries is low, and the pH there-
fore drops quickly as acid is produced. Pathogenic
organisms are inhibited by a fast acid production, so
the addition of starter cultures, either as a pure cul-
ture or by “backslopping” promotes acid production
and contributes to the safety of the fermented prod-
uct (Nout et al. 1989).
The potential and the need for upgrading tradi-
tional fermentation technologies have initiated con-
siderable research (Holzapfel 2002). In some recent
studies of spontaneously fermented cereals, the LAB
and yeasts have been isolated and identified as a first
stage towards developing starter cultures for small-
scale production of traditional fermented cereals.
Muyanja et al. (2003) recorded that bushera, a tradi-
tional Ugandan fermented sorghum beverage that
contains high numbers of LAB, was usually con-
sumed by children after one day of fermentation as