industry environments.The regularbioaerosol assays are comparatively cheap,
relatively fast to carryout and do not require much work. However, it is
importantto keepin mindthat stressesimposed on the cells in the airborne state
mayrenderthemnon-culturableand the methodsthat rely on the growthof
microbes for theirdetectioncan seriously underestimate the number of viable
cellswithina sample (Griffiths& DeCosemo,1994).The ratioof the total
number of microscopic cellsand the viable numberof organismsdetected may
rangefrom5 to 200 in foodindustry. The actual microbial countmaybe biased
by severalorders of magnitudeif concentrationsare givenonlyin termsof
viablemicroorganisms(Nielsen & Breum,1995).
As the informationlevelneededon bioaerosol quality increases or joins
together with more effective or targeted sampling techniques, the more
advanced assaymethodssuchas molecular and fluorescence methodscan help
to achievethe preciseknowledgeneeded. The morespecificthe methodsare, the
biggerthe costsmaybecome. Theinformationgainedmay, however,be a
multiple of that frombasic bioaerosolmonitoring.
In general, air qualitymonitoring should be donewithone approved sampling
and assayingtechnique to be ableto comparethe results overthe longterm.
However, as the process,raw materials, employees, equipment and otherpara-
metersmaychange, it is recommended that the bioaerosolqualityis checked
fromtimeto timewithanothersampler as wellas withanotherassaymethod.
This helps to prevent unexpected air quality problems despite regular
monitoring.No single methodcan completelydemonstrate all the microbes
presentin bioaerosols.
37.7 Interpretationof bioaerosolresults
Thereare no general limits for microbial concentrationsin the foodindustry air.
The bioaerosol results haveto be evaluated case-specificallyat eachprocessing
place.It is normally impossible or at leastdifficult to comparebioaerosolresults
fromdifferentfoodindustries, fromthe sameindustrytype or evenfromdifferent
locationsin the same factory. In particular one should neverdirectlycompare
resultsobtainedwithdifferentsamplersor differentassay methods.In addition
samples takenwiththe same sampler and analysedthe samewaymaynot be
totallycomparable if the samplingparameterssuchas time, collection surface
and sometimes eventhe samplecollector havechanged betweenthe samples.
The best and fastestway to utilizethe bioaerosol resultswouldbe a situation
whereall the productcontaminants of air in eachspacewere identifiedand
known. In addition,the concentrationsthat do not causeproduct contamination
withinthe product shelf-lifeshouldbe known. Successful bioaerosolcontrolling
demands knowledge of contaminant concentrations in relation to different
product exposure times.Thisdemandsmuchresearchand is rarely donein the
foodindustry.Without this kindof information,bioaerosol results are only
indicative.
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