of the mostimportant topicsin dailylife. Therefore the industry should be eager
to provefoodquality.In this connection the mosteffectivewayis to verify
qualityfromthe production sideof raw material via industrialprocessingto
supermarket shelves(tracing`fromfarm to fork'). The mainrequirementsfor
this approach are automation and miniaturisation; i.e. the need for an
instrumentation that can workwithout supervisionand that can be implemented
in an existingprocesstechnologyin ordernot to disturb the ongoing process.
So far, the existingmethodscannotservetheseneedsof regulatoryagencies
and foodproducers. Futurereal-time testing withreliable sensor technologywill
providevalue to foodproducersthroughreduced treatmentcostsand reduced
product recalls.As the demandsfor foodsafety increase, the requestfor fast
sensingtechnologieswill onlyincrease. A miniaturisedtotalanalysissystem,as
described in Section 19.3.3for biological and medical applications,couldfulfil
theserequirements.
19.3.1 Chemical gas sensors
Chemical gas sensors have become a useful industrial toolfor bioprocess
monitoring.Theyrepresenta cost-effectivetoolfor rapid assessment of the
chemical and microbial statusof raw materials, processstreamsand end-product.
Extensiveand costlyreworkor disposalof products that do not fulfiltheir
specificationscan be prevented.Mostbiological processes that can be foundin
the foodand biotechnologyindustriesare probablysuitedfor the applicationof
gas-sensor arrays.This is because theyinvolvesignificantconcentrationsof
aromatic compounds or volatile secondary metabolites produced by the
microorganisms.In a typicalbioprocess, cellsare grown understerileconditions
in tanks(bioreactors)on liquidmedia that provide essentialnutrients,vitamins,
etc. The productsfrombioprocesses rangefromenzymesand single cell protein
to biopharmaceuticals, whichnaturallyall imposehighdemandson product
qualityand safety. Gas sensor arraysystems havebeenshown to be veryuseful
for bothquantitativeand qualitativebioprocessmonitoring,which allowsreal-
timedeterminationof cell status, growthrates and product concentration(Liden
et al., 2000;Mandeniuset al., 1997).Anotheradvantage withthis technology is
that it can be usedto discoverbacterialcontamination on-linein real timein the
bioreactor tankafteronly a few hours of processing,whichis a significant gain
compared withtraditionalmicrobiological methods. The applicationof non-
invasive on-linemonitoringmethodssuchas gas-sensor arrayscouldtherefore
certainly contributeto improve the quality of bioprocessedproducts. Thishas
alsobeendocumentedby several studies(e.g.Bachingerand Haugen,2003;
Dickertet al., 2003;Pasiniet al., 2004).
19.3.2 Biosensors
Although the marketis generatinga needfor pathogen-detectingbiosensors,
onlya few are commercially available or are approachingcommercialisation
Improvinghygieniccontrol by sensors 299