Fundamental Food Microbiology, Third Edition - Fuad Fathir

216 FUNDAMENTAL FOOD MICROBIOLOGY
antigens. Probiotics containing beneficial gut bacteria can have a suppressive effect
to such reaction by stimulating the production of antiinflammatory cytokines and
reducing allergic reaction in sensitive individuals. As the results are not consistent,
this at present is regarded as only a theory.
G. Miscellaneous Benefits
Many other health benefits of probiotics have been claimed, such as prophylaxis against
urinogenital infection, increased calcium absorption from the intestine, stimulation of
endocrine systems, growth promotion, and prolongation of youth and life. Many of
these are merely claims and are yet to be proven by proper scientific research.
V. SOME ASPECTS TO CONSIDER
The health benefit theory of fermented foods and beneficial intestinal bacteria is
controversial. Although an association effect, i.e., some benefits from their consumption,
cannot be denied, many studies have not been able to prove the benefits without
doubts. As suggested before, the differences in study methods could be one reason
for the differences in results. In designing these studies, several aspects have to be
recognized. There are definitely differences in human responses, but there are also
differences in bacterial responses. In selecting bacterial strains, the following considerations
are important. 8–11
A. Strain Variation
Beneficial strains differ in adherence ability and specificity (Figure 15.1). An
adherent strain should probably be favored over a nonadherent strain. Also, strains
adherent to humans should be preferred over strains adherent to other species.
The selected strains should have a strong adherence property. The adherent
property can be lost during long maintenance under laboratory conditions. Many
studies have been conducted without even knowing the source and identity of the
strains. In selecting a strain for a study, the following factors need to be considered.
B. Sensitivity to Stomach Acids
Survivability of strains to low stomach pH varies greatly. This effect can be reduced
by either reducing stomach acidity with food or by using strains that are proven
resistant to acid environment.
C. Viability and Injury of Cells
Cells of beneficial bacteria when frozen, dried, exposed to low pH, high salts, and
many chemicals can die. Among the survivors, many can be injured and killed by