can be assignedto eachof the above-mentionedcriteria(Griffiths & DeCosemo,
1994).
It is likelythat the overalllevelof microbes will requiremonitoring,although
the detectionof potentialpathogensor specificspoilageorganismsmayalso be
required.The major concernis probably for the viablemicrobescontaminatingthe
food products.Viablecountsare thereforelikelyto be moreimportantthanthe
total particlecounts.If the samplingmethodselecteduses agar mediathe choiceof
the collectionmediais an importantparameter.Generalagar mediafor bacteriaor
fungi supportmost species.However,if the aim is to isolateand identifyspecific
microbes that can contaminatethe productin questionit is vitalto use a medium
that particularlysupportsthosecontaminantsthat are relevantand supported also
by the product. The informationfroma generalmediumdoesnot indicatewhether
such strainsare ableto growon the relevantproduct (Kureet al., 2004a).
Combinationof general and specificmediadescribesthe overallsituationof the
processing.Moreoversensitivemethodsmay be required, sincelow levelsmust be
detectedas in the monitoringof pathogens or potentialpathogens.In both the food
and pharmaceuticalindustriesthe speed with whicha result needsto be obtainedis
a questionof economics(Griffiths& DeCosemo,1994).
The samplingtimemust be consideredaccordingto the process and aim of
sampling.In the food industry, monitoring the bioaerosol situation during
processingis importantbut also the situation aftercleaning procedures can give
additionalinformation.According to Parretand Crilly(2000),importantinfor-
mation fromthe samplingperiodincludes: locationand area of the site, date and
timeof sampling,test temperatureand moistureconditions,functioning of the
ventilationsystemduringsampling, personnelin the area,volumeof air sampled
along withsamplingperiod,collectionmedia usedand incubation timeand
temperatureused.In additionall unusual operationsor eventsshould be recorded.
Choosingthe samplingplacesin the processenvironmentis an importantpart
of accomplishingusefulbioaerosolresults. It is valuable to lookinto air flows in
the processenvironmentbeforesampling, sinceair flows can varyand a sample
taken fromone place maybe totally differentfromsampletakenfroma metre
away. Smokegeneratorsare available that can be applied to studyand visualize
air movements.Bioaerosolresults are more reliableand givemore precise
informationof the product contaminationthroughan air routeif the samplesare
taken as nearthe productlinesas possible.The numberof samplesand sample
places in one areashould also be considered according to air movements,
product risk leveland the overallknowledge needed.
37.4 Bioaerosolsand bioaerosolsamplers
Aerosols exhibitcomplexaerodynamicbehaviourresultingfroma combination
of physical influences that include Brownian motion, electrical gradient,
gravitationalfield,inertial force, electromagnetic radiation, particle density,
thermal gradients,hygroscopicity and humidity (Kang & Frank,1989d). The
622 Handbookof hygiene controlin the foodindustry