direct replacement for microbiological testingbut provide complementary
informationand shouldbe usedas part of an integratedstrategy (seeSection
36.4.1)
The marketfor rapidtest methodsis predictedto increase(Griffithet al.,
1997),althoughit is probablyfair to say the ideal test methoddoesnot yet exist
(see Table36.5)and theiruse needsto be consideredin relationto the typeof
businessand the foodproduced (see Table36.6).
36.3.1 ATPbioluminescence
ATP,or adenosine triphosphate, is the universalenergy currency, or donorfor
metabolic processes,in all livingcells.It is presentin viable microorganisms
(notviruses) and in foodstuffsin variable amounts,depending upontheir
composition.The ATPbioluminescence assay works on the principle(see Fig.
36.6)that ATPin food/food residues and microorganisms,in the presenceof an
enzyme/substrate complex, leads to lightemission. The light is measured
quantitatively in a luminometer (light-detectinginstrument),withresults avail-
able in 10±30seconds.The amountof lightemittedis therefore proportionateto
Table36.5 Characteristicsof an idealassessmentmethod
∑ Detectsmicroorganismsand foodresidueswithsufficientsensitivity
∑ Worksequallywellon wet and dry surfaces
∑ Goodrepeatability/reproducibility
∑ Easyto use
∑ Rapid
∑ Cheap
∑ Foolproof/recordable/tamperproof
∑ Resultscan be usedin trendanalysis
Table36.6 Considerationsin usingrapidchemicaltests
Universalityof test Residue/moietydetectedis foundin a widerangeof foods
chemical
Quantityin food Amountof the detectedchemicalcontainedin differentfoods
Sensitivityof tests Lowestlevelof chemicalresiduethat can be detectedby the
test
Other Cost± especiallyimportantif manytestsundertaken
Time± resultsobtainedrapidlyto allowcorrectiveaction
Simplicity± easeof use by all staffwithminimumtraining
Documentation± abilityto read/recordresultsdigitallywith
timeand date
`Horsesfor courses'! Choiceof test selectionvarieson individualcircumstancesand
typesof foodproduced
604 Handbookof hygiene controlin the foodindustry