between the preparations may be raised. It is important to take
viability into account because many strains exert effects in the
nonviable form as well (21, 22). Further studies on viability and
health effects are clearly needed.
CONCLUSIONS
It is important to ensure that the specific properties of a probiotic
used originally as selection criteria are also targets for
quality assurance. This is an important prerequisite for any
health claims and should be continuously controlled if the health
claims are approved for use. Thus, functional food regulations
should take into account strain properties and their stability during
industrial processing and use. On the other hand, not all
selection criteria are always necessary for in vivo functional
effects. Each important strain property and its influence on
health should be assessed in relation to the clinical effects
observed in various studies. In vitro test protocols can be readily
adopted to examine the maintenance of a strain’s ability to tolerate
acidic conditions, survive and grow in the presence of bile,
and metabolize selective substrates.
Adhesion characterization may be an important quality-control
method for assessing the surface structure of probiotic bacteria
and related gut barrier effects. Adhesion has been related to
immunogenic effects, shortening the duration of diarrhea, and
other health effects. If adhesion is modified during industrial
processes, probiotic effects may consequently also be altered.
Adhesion properties and their dependence on processes and
process changes should be monitored. Suitable models include
adhesion to intestinal cells, such as Caco-2 cells, and binding to
human intestinal mucus preparations. At least 2 models should
be used for routine quality control of adhesion of probiotic
microbes because this would allow different adhesion characteristics
to be measured.