636 Part VI: Fermented Foods
include lactulose, fructooligosaccharides, and inulin.
It has been suggested that the best probiotic results
may be obtained by using a combination of a prebi-
otic (such as oats) and a probiotic organism (Chara-
lampopoulos et al. 2002). In this way, the total phys-
iological effect of the food could be increased.
In order for a probiotic product to have a physio-
logical effect, it has been suggested that it should
contain at least 10^6 cfu/g product, and that daily
intake should be at least 100 g (Sanders and Huis
in’t Veld 1999). The final acidity in the product has
been shown to be of critical importance for the sur-
vival of probiotic bacteria during storage (Mårtens-
son, Öste and Holst 2002). Many probiotic bacteria
do not tolerate a pH below 4.0, and fermented cere-
als frequently reach this pH due to the poor buffer-
ing capacity of the substrate. In addition, the physi-
ological state of the probiotic organisms at the time
of storage also determines their survival. Organ-
isms that show poor growth during a fermentation
period are more likely to die out during cold stor-
age. This necessitates careful formulation of the
product as well as selection of the right probiotic
culture.
The choice of a substrate for a probiotic food is
partially governed by the tolerance of the food to-
wards heat pasteurization or even sterilization be-
fore fermentation, and cereal mixtures lend them-
selves well to this treatment. Probiotic products
require fermentation at around 37°C for 8 to 18
hours, depending on substrate. The suitability of
such conditions for the growth of pathogenic
organisms necessitates strict adherence to hygiene
both before and during fermentation. A fast lactic
acid development in the product during fermenta-
tion is a critical step, and the growth of probiotic
organisms in cereal products is greatly stimulated
by the addition of malted flour (either of the same
grain or of barley malt) or milk, due to the in-
creased availability of fermentable sugars, peptides,
and amino acids. For probiotic weaning foods, the
use of malt has a further advantage since at a given
viscosity, the product has a higher nutritional den-
sity.
Probiotic cereal foods are in their infancy, and the
future will probably see further development in this
type of product. New strains with proven probiotic
efficacy and good flavor-forming abilities will in-
crease the range of probiotic products available.
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