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KANG AND FRANK

thal airbome contamination is sirongly suspccicd as a vehicle for paihogens cmcring into products.

An important part of ihc PDA Dairy !ni(iative Inspec-lions has been Ihe sampiing of finished products for thc prcsence of Listeria. Y er sini a. Salmonella, and Campylo-bacier. Nonę of lliese paihogens can survive the pasieuri-zation proccss. As of 1986 the PDA found 26 planis which produccd coniaminated products (72). Among thc 26. eighi contained palhogcnic Listeria in their packagcd products. Since these potential paihogens do not survivc pasteuriza-lion, these plants probably have post-pasteurization contamination problcms (6,7,72). Diny fillcrs and aerosols have been reported as thc sourcc of pathogen contamination (72).

In one Siudy (12), about 25% of non-mold colonies from the air of a fluid milk plant wcrc Gram negative rods and 24% of total colonies isolatcd could grow in 5 d at 10°C. Though thc origin of these Gram negative rods is not elear, their prcsence in the air of the packaging area is of both public hcalth and product shelf life significance. Plakhotya (60) found that Salmonella in an aerosol condi-tion could survive up to 4.5 h, indicating the potential for airbome dissemination.

Controlling air ąuality in food processing areas

Aerosols of bactericidal or viricidal agents have been used in dairy industry for controlling airbome bacteria and bacteriophage. These agents have included various forms of chłonne, glycol, alcohols and quatemary ammonium. cornpounds (8,10). Fogging must be limited because of potential health effects on exposed workers. For cxample. a chłonne fog of 500 ppm will reduce airbome microflora, but over 10 ppm causes excessive human discomfort (32). In addition. fogging will be less effcctive if the source of the aerosol is not controlled. Aerosols often originate from unclean surfaces as previously discussed.

Ultra-violet radiation can be used to decrcase airbome microflora, but its use is also lirniled by worker safety.

The use of laminar air flow with HEPA (high efft-ciency paniculate air) filicrs is highly recommended at critical points (3536.40). HEPA filters rernove 100% of panicles that arc greater than 0.3 Jim in size and conse-quently will rcmove all viable bactcna.

Stersky et al. (67) used a bipolar-oriented electrical field to reduce thc level of viable acrosolized microorgan-isms. They found thal a field of I4K to 20K volts reduced the mcan airbome population by 31 to 59% during regular foreed ventilation, depending upon the microbial specics.

Vickcrs (73) concluded thal the adoption of design condifions used in ‘clean air* rooms and cnvironmcntally controlled work stations for dairy packaging and other critical hygiene areas is requircd to ensurc productlon of safe dairy products with long shclf-lile. These design con-ditions include physical separalion of critical and non-critical hygiene areas. thc adoption of air-locks, pressuri-zation of critical hygiene areas. and usc of HEPA filters. also hcating. veniilating and air conditinning (HVAC) sy.stcms should bc designed for casy dcaning and must be

adequately maintained (28). The engineering aspcct of air flow control within a dairy processing plant are discussed by Heldman and Hedrick (35). New dairy processing fa-cilities are being designed and operated using these clean room concepts (42).

Considering the potential imporlance of the problem, there is lidle published rescarch on air quality in modem food processing planis. Additional study is necded to pro-pose reasonable air quality guidelines in dairy and food processing plants and to recommend appropriate monitoring methods. Closcr attention to air quality at critical processing points is required to reduce thc risk of product contamination, but liltle inforrnalion is uvailablc on the exient of the cunent problem.

ACKNOWLtOCMŁNTS

Prcparation of this manuscript was supported by State and Hatch funds allocated 10 ihe Georgia Agricultural Eapcrimcnt Stntion.

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