simple modelto quantify recontaminationvia the air was developedby Whyte
(1986):
RcàCairvsAt=W Ö 2 : 7 ÜwhereRcis the contaminationrate (cfu/g),Cairis the concentrationof micro-
organismsin the air (cfu/m^3 ),vsis the settlingvelocity(m/s),Ais the exposed
product area (m^2 ),tis the exposure time(s), andWis the weightof the product
(g).
For example,duringthe production of slicedmeat, the product withAà
140 cm^2 andWà17 g is exposed to the air for 45 s, resultingin a contamination
level of 4 cfu/product or 0.2 cfu/g(Cairis 3.39log cfu/m^3 andvsisˇ2.59log m/
s) (denAantrekkeret al., 2003).Thismeans that when the product is sterile,
contact with contaminated air causes an increase in concentrationwith 4 cfu/
product.
Although these simplemodels do not incorporate all factors that maybe of
relevance, theycan be usedto providean indication of the importance of air
contamination comparedwith the initial contaminationof the product and
possible growthand inactivation duringthe production process.
2.4 Conclusions
Quantitativemethodscan helpto determine whichmicroorganismsgivethe
highest contributionto the number of foodborneillnesses.Thishelpsto decide
whichpathogen(s) one should focuson in orderto reduce the number of
illnesses.Thesame accounts for the products that are relatedto foodborne
illnesses.Quantitativemicrobiologycan be usedin controllingfoodsafetyin a
farm-to-fork approach.Usingsuchmodels, one can try variousapproaches to
obtain the sameFSO.
Moreworkneedsto be done to incorporate recontaminationin predictive
models. The modelsavailableat the moment,althoughsimple,can alreadybe
applied to determine the importance of (re)contamination compared withgrowth
and inactivation of pathogens.
2.5 References
ADAK, G. K., LONG, S. M.andO'BRIEN,S. J.(2002),Trendsin indigenousfoodbornedisease and deaths,Englandand Wales: 1992 to 2000',Gut, 51 (6), 832±841. CAC(CODEX ALIMENTARIUSCOMMISSION)(2004).ALINORM04/27/13AppendixIII, p. 83. DENAANTREKKER,E. D., BOOM, R. M., ZWIETERING,M. H.andVAN SCHOTHORST,M.(2002), Quantifyingrecontaminationthroughfactoryenvironments± a review',Int. J.
FoodMicrobiol., 80 (2), 117±130.
DENAANTREKKER, E. D., BEUMER,R. R., VAN GERWEN,S. J. C., ZWIETERING,M. H., VAN
SCHOTHORST, M.and BOOM, R. M. (2003), `Estimating the probability of
44 Handbookof hygiene controlin the foodindustry