However, evena low number of bacteria in the packagingmaterial could be of
concern for aseptic foodsif bacteriamigrate acrossthe package (Suominenet
al., 1997).
The routesof contaminationfromthe packagingmaterial to foodincludethe
surface, cutting dustor directcontactwiththe raw edgeof the paperboard. To
eliminatethe raw edge,cartonsintendedfor liquidfoodswithlongshelf-life and
for aseptic packaging are usually skived (a carton configuration which
eliminatesraw edges) (Pirttija»rvi, 2000). The dust generatedduringthe skiving
process maybe scattered on the inner surfaceof the carton.Duringextended
storageit has beenfoundto be an indication of morefrequentspoilage of skived
chemi-thermomechanical pulp (CTMP) cartons compared with non-skived
(NordFood, 1999;Pirttija»rvi, 2000).
Withscanningconfocallasermicroscopy(SCLM)Suominenet al.(1997)
studied the microbiologicalbarrier propertiesof food-packagingpaperboards,
coated withpolyethylene,mineral pigmentor a biodegradablepolymerand of
high-densitypaper. Theyreportedthat spatial distribution of microscopically
observablebacterialcells is uneveninsidethe paperboard. Thenumbers of
bacteria at the interfacebetween the polyethylenecoating and the cellulose
fibres were100±200timeshigherthaninsidethe cellulose matrix. The bacteria
in the interface and in the mineral coatinglayergrewin responseto access of
nutrientsand water,whereas no growthwas observed insidethe fibreweb,even
afterextendedexposure for up to 90 days.Thefactorlimiting growth and
migration of bacteria insidethe fibreweb was probablythe limited accessto free
water, evenunder conditionsof excessive moisture. Accordingto the authors,
the microbesresiding betweenthe paperboard and its polymercoatingfacingthe
foodcould potentiallycontaminatethe food.Mineral-coatingpigments were
reported to be a sourceof contaminating microbes. Therefore the use of high
hygienic-quality surface-sizingchemicals is essential(Suominenet al., 1997).
24.3 Improving hygienic productionand management
Microbialmanagement is divided intotwomain strategies: to prevent the
entrance of microorganismsto productionpremisesand to eliminatemicro-
organismsfromproduction facilities if they haveenteredthe premises. As sterile
conditionsare impossible the preventiveactionsshould be focused so that the
restrictionof microorganismsis economicallyand operationallyreasonable.
Focus should be on microorganismsthat causeharm,damageor danger to
product, process, worker, environmentor customer. Theultimate goalof all
these activities carriedout in microbial risk management is prevention.
The control of microbial growth in a paper machine environment is
traditionallybasedon the use of biocides (Fig.24.1).However, the amount of
microorganismsis not alwaysproportional to the severity of microbial problems.
The mostimportantfactors in the use of biocides are selectionof suitable agents
and the optimal feedingstrategy.Owing to variability and complexityof the
386 Handbookof hygiene controlin the foodindustry