∑ staffconcernedwiththe operationof suchequipment;
∑ packagingmaterials;
∑ finished products.
There is a philosophy with considerable support that states that all other
requirementsshouldbe consideredas secondaryto thesefive basicrequirements
and, wherever possible,shouldbe kept out of the high-riskprocessingarea.This
aids in cleaning and disinfection and thus contamination control. These
secondaryrequirementsinclude:
∑ structural steel framework of the factory;
∑ service pipeworkfor water, steamand compressedair; electricalconduitsand
trunking;artificiallighting units;and ventilation ducts;
∑ compressors, refrigerationunitsand pumps;
∑ maintenancepersonnelassociatedwithany of theseservices.
8.4.2 Heat-treated product
Where a product heat treatment formsthe barrierbetweenlow and highrisk (e.g.
an oven,fryer or microwavetunnel), the heatingdevicemustbe designedsuch
that as far as is possible, the deviceformsa solid,physicalbarrierbetween low
and highrisk.Where it is not physically possible to forma solidbarrier,air
spaces around the heatingequipment shouldbe minimisedand the low/high-risk
floor junction shouldbe fullysealedto the highest possible height.Other points
of particular concernfor heatingdevices includethe following:
∑ Heating devices be designedto loadproduct on the low-risk side and unload
in highrisk.
∑ Goodsealsare required betweenthe heatingdevice surfaces,whichcycle
through expansion and contractionphases, and the barrier structure that has a
different thermalexpansion.
∑ Sealing is particularlycritical at the floor levelwhereovensmaysit on an
openareaor `sump'. Sumpscan collect debrisand washing fluids fromthe
ovenoperation whichcan facilitate the growth ofListeria, and theseareas
should be routinelycleaned(fromlow risk).
∑ Ovens shouldnot drain directlyintohighrisk. In addition,whenbeing
cleaned,cleaningshouldbe undertakenin sucha way that cleaningsolutions
do not flowfromlow to highrisk.
∑ If ovenracks of cookedproduct haveto be transferredinto highrisk for
unloading,theseracks should be returned to low risk via the ovens,withan
appropriatethermal disinfectioncycleas appropriate.
∑ Anyventilation systemin the cookingareashould be designed so that the
area is ventilated fromlow risk;ventilation fromhighrisk can drawinto high
risk largequantitiesof low-risk air.
∑ Early installationsof opencookingvessels (kettles) as barriers between low
and highrisk,togetherwith(occasional)low level retainingor bundwallsto
prevent watermovement acrossthe floorand barriersat waistheightto
158 Handbookof hygiene controlin the foodindustry