examples of good practice. Obviously, since `deep cleaning' operations
(thorough cleaning normally applied after production) produce high
concentrationsof aerosol, it is essentialthat aerosols are allowed to settleor
be removedby the air-handlingsystemaftersuchcleaning. Ideally, the air-
handling systemwouldnot be usedduringdeepcleaning or otherwisebacteria,
made airborne during the cleaning operations,couldbe collected on the cooling
coilsof the refrigerationsystem. Operatingthe air-handling system at full
extractafterdeep cleaning is goodpracticeif possible.5.6 Future trends
The developmentof the high-care and high-risk chilled foodsectorshas seenan
increase in the use of zoning in factories and morerecently,for somefactories,
the use of cleanroomtechnologies.Bothof thesetopics are coveredelsewhere
in this book.Havingincreasinglycleanerenvironments closestto the foodis a
goodconcept. The questionarisesas to the length scaleon whichthe graduation
or zoningis carriedout. Currently,in mostchilled foodfactories in the UK,
manufacturing shortshelf-life products, the mainzonesare high-care/risk areas
and low-care areas. Somefactories are,in addition,installing localisedair
delivery systemsthat provideair at an evenhigher quality, than is usual,directly
towards the food.Burfootet al.(2000)showa numberof differentdesignsthat
havebeenconsidered for this purpose. These includethe direction of cleanair
vertically or horizontally towards the foodsor the circulation of cleanair around
the foods. Localised air delivery has been found to reduce the airborne
contamination of foods. A furtheradvantageof these systems is that theycould
provide a potentialenergy savingif coldair is supplied locallyallowingthe
factory to be run at a highertemperature(Burfoot et al., 2004). Also,by
maintainingthe foodtemperature they reduce the needto cool the productsafter
theyleave the productionarea.However, for this approach to providehigh
energy savings,most ingredients needto have been cooled priorto enteringthe
high-care/risk area.The use of localisedair deliveryis beginning to be applied
but manysee that suchapproachesare restrictedto products wherean extension
of shelf-lifeis a majorgoal.For products suchas preparedsaladsthat have
significantmicrobial load, or products that havea veryshortshelf-lifedue to
quality degradation ratherthanmicrobial spoilage, providingultra-clean air
close to the product probably has less applicationthanin the caseof other
products suchas slicedham.
5.7 Sourcesof furtherinformation and advice
There are manysourcesof information and advice relating to airborne con-
taminationand air handling. Otherchapters in this bookclearly provideasso-
ciated information.The engineering research and foodresearch organisationsare100 Handbookof hygiene controlin the foodindustry