contact, or establishing whether a product contains moreallergenicmaterial than
a set limit. The key considerationwithrespectto assaydevelopment should
therefore be the purpose of the assay. Theallergenic protein, althoughthe
obvious candidate,maynot alwaysbe the optimalchoice. However, detecting
the proteinis probably the mostcommonapproachand it is thereforeappropriate
to discussthe optionsavailable.
In developingan assaybased on proteindetection, twomainchoicesof
methodologyexist:monoclonaland polyclonalantibodytechnology.Bothhave
advantagesand drawbacks.As monoclonalantibodiesrecognisesingleepitopeson
proteins,this technologyusuallyresultsin a highlyspecificassay,witha relatively
low incidenceof cross-reactivity,evenwithcloselyrelatedproteins,providedthe
antibodieshavebeencorrectlyscreened.Theoreticallythereis alsoan endless
supplyof antibodywith exactlythe sameperformance characteristicsas the
originalantibody.However,the narrowspecificityof the monoclonalantibodycan
also be its Achilles'heel,as detectionof the proteinof interestwill take placeonly
if the antibodybindingsite remainsintactand accessiblein the variousfood
matricesin whichthe proteinmaybe present.Polyclonalantibodytechnology
relieson the productionof a rangeof antibodies,eitherto a singleproteinof
interest,or to all the proteinswithinthe food,dependingon the preparationused.
Thisprovidesa detectionsystemthat is less likelyto fail completelyto identifythe
presenceof proteinsof interest,althoughquantitationmay remainproblematical,if
processingaltersthe relativeproportionsof the differentimmunochemicallyactive
proteinsin a food.However,the maindrawbacksof polyclonaltechnologylie in
the needfor extensivepurificationproceduresthat mayneedto be appliedto the
protein(s)of interest,as well as to the resultingantiserumto ensurespecificityand
absenceof unwantedcross-reactivity,togetherwith the needto developprocedures
to ensurebatchto batchreproducibility.
Once the technology itselfhas beenselected, there remain severalpossibili-
ties in developing immunoassays basedon protein.As discussed, monoclonal
technologyresults in a highlyspecificdetection system, but it can nevertheless
be broadenedby usinga combination of detection antibodies against different
epitopes of the same protein, and/or differentproteins. However, beyonda few
proteins,this becomes complex to optimise. Polyclonal technology leaves open
the choice of the material againstwhichthe antiserum can be raised.Thus it can
be as general as a protein extractof the wholefood,or as specific as a highly
purified protein.
Detectionof the protein, or proteins, maynot be necessaryor eventhe
methodof choicein all instances wheredetection of allergenicresiduesis
sought. Insteada markermolecule, for whicha robust and sensitiveanalytical
methodexists, and whichis alwaysfoundin a known ratioto the proteins,can be
used.An example wouldbe lactosein milkwhichcouldbe usedas a tracerfor
estimatingthe amount of milkprotein left on a line by cross-contact.Similarly, a
marker compoundcould be usedin supplier audits.However,onlymeasurement
of the protein could helpan allergicindividualdecidewhethera particular
product is safe to eat. Similarly, complianceactivities by foodsafetyauthorities
370 Handbookof hygiene controlin the foodindustry