Disinfection of packaging
High-intensity UV light to fight bacteria in packagingmaterials to keep a yoghurt edible for as long as possible high hygiene requirements need to be met alongside the quality of theproduct, as early the filling and packaging process. Inparticu- lar, microbiologically sensitive bulk products such as foodre-
quire packaging materials with low germ counts. The surface of these materials can be treated with a number of methods. Compared to chemical and thermal methods, UV light radiation treatment is a more reliable and at the same time more economically efficient method.
Disinfection with ultraviolet light
In general, the method used to sanitize bacteria from packaging ma- terialsisdisinfection,notsterilisation:Ultravioletlightatwavelengths of 254 nanometer (nm) is more energy-rich than the terrestrial UV light of the sun. This especially short wave UV light destroys the DNA of all micro-organisms. When installed purposefully, viruses are dis- abled in seconds and micro-organisms such as bacteria, yeasts and fungi are killed in an environmentally friendly manner, without the addition of chemicals. For a whole series of micro-organisms, the le- thal dose of UV radiation is known and this is the dose after which the cells can no longer maintain their metabolism and can also no longer multiply. Because of the cell wall structure, the lethal dose for different pathogens is distinctly high. Consequently, bacteria such as salmonella and coli bacteria, which have a comparatively thin cell wall and can thus only slightly block the UV radiation, are extremely vulnerable and are very quickly destroyed. On the other hand, mould spores protect themselves against UV radiation with a thick cellwall,which can even be pigmented. To kill these, a UV dose which is 10 to 100 times higher than that required for bacteria is needed.The required lethal UV dose is an important parameter in the design andselectionofsuitableUVradiationsources.Machinespeed,geometry andshapeofthepackaging(forexamplecuporsealingfoil)arefurther criteriainthedesignofaneffectivedisinfectionprocess.Thenecessary UV dose is calculated by multiplying the irradiation power (intensity)of theUVlampbythelengthoftimethatirradiationtakesplace.
tensity of the radiation is also dependent on the distancebetween the UV cassette and the packaging. The UV intensity of a lamp decreases with the increase in operating hours. At the end of the lamp operating life there must still be sufficient high UV intensity to ensure a suitable disinfection power and the necessary lethal dose in the given radiation time. Experience with Yoghurt filling for example has shown that pots ofadepthof150millimeters(mm)canbeeffectivelydisinfectedwithin foursecondsandsealingfoilsintwosecondsatthesameintensity.
UV disinfection is used especially for the packaging of acidic fresh milk products,suchasyoghurtandkefir,whicharekeptinthecoolchain,inor- der to improve shelf life. This means that the dairy has significantly fewer returns of spoiled product, saving time, effort and cost ofdisposal.
Up to 99.9 percent germs removed – Fraunhofer proofed
Evenmoreintensivelyandreliably,theHeraeusPremiumUVmodulesre-ducethenumberofgermsonthesurface.Thelatestpowerfulmoduleshave been developed especially for UV disinfection in thefoodindustry.Theyremoveupto99.9percentofgerms.Thisisproofedbythereportof the Fraunhofer-Institute for Pocess Engineeringand Packaging,Freis-ing,Germany.AccordingtoamethodoftheassociationVDMA,Frauhoferhas tested the efficiency of the decontamination by usingPremiumUVModulesagainstcertainmicro-organisms(conidiosporesofAspergillusni-ger,endosporesofBacillussubtilis).Duringthiscountreductiontestthreerespectivelyfiveloglevelshavebeenachievedwithinadistanceof20mm.The use of a novel lamps technology enables high intensities andasub-stantiallylongerservicelife.TheuseofjustoneUVcassettereducestheexpenditure for servicing and associated costs. The shortexposuretimesalsocontributetoreducingoperatingcosts.Dependingonthematerial,betweentwoandfoursecondsaresufficientforthedisinfectionprocess.TheUVlampisvirtuallytheonlyconsumablenecessary.Ithasaservicelifeofupto12,000operatinghourswhichisequaltotwoyearsofactualuseat24hoursofoperationperday.Duringthattime,thePremiumUVmodulecansteriliseabout173millioncupsonamachinewitheightlanes.Thismeansaninvestmentofjust0.03Eurocentspercup,alotlessthanoneEurocent.
Easy handling - high safety
In addition to the economic benefits, the Premium UV modules fea- ture easy installation and operation. The modules can simply be in- stalled or retrofitted to existing filling and sealing plants.
Due to the integration into the respective HACCP concept, the quartz glass plate, the temperature and the emitter function can be moni- tored automatically. The quartz glass covers of the UV cassettes are provided with a breakage detector patented by Heraeus and thus part of the HACCP concept. If a quartz glass plate breaks, thedetector sends a signal to stop the filling plant immediately. The type of protection of the Premium UV module is IP67, so it can also be used without re- strictioninwetenvironmentsofaCIP-machine(CIP=CleaningInPlace). Translucent plastic doors, e.g. made of Makrolon, are sufficient to pro- vide protection against theradiation.
Electronic control unit and ventilation are combined in a new me- dia box to make retrofitting even more easy and reduce the space requirement. Based on the modular design principle, one to three UV cassettes can be operated with one media box. Expensive watercool- ing is not used as the Premium UV modules are cooled with ambient air. The ventilation provided by one media box is sufficient to cool up to three UV cassettes. The media box is stainless steel design and EMC-protected (electromagnetic compatibility) and can be operated anywhere in the world at supply voltage frequencies of 50/60 Hz. The box has two 180 – 264 Volt connection sockets. Premium UV modules are equipped with an operating hours counter and an on/ off lamp signal to make the entire monitoring processeasier.
As an option, the Premium UV module may be equipped with a pat- entedquick-startsolution.Thiswillreducethewarm-uptimefromabout fiveminutesto90seconds,sothefillingprocesscanstartmorerapidly.
High-intensity and nevertheless cold
Duetotheirslimshape,PremiumUVmodulesareusedinparticularto sterilisepackagingmaterialsinin-linefillingmachineswithfourtotwelfe rowsofcups.Asastandard,thenewPremiumUVmodulesareavailable in three sizes but they may also be adjusted especially to the machine enviroment. Although the UV cassettes generate a high irradiance, the UV light is cold. Therefore, the packaging material is not heated. This makes the disinfection method perfectly suited for the treatment of heat-sensitive materials such as plastic cups and sealingfoils.
Taking account of various dimensioning criteria and with a suffiently highirradiance,UVdisinfectionisusedasasimple,fastandreliablemeth- od in continuous operation in filling plants. However, outside the food production industry as well, e.g. to disinfect packaging materials in the pharmaceutical and cosmetics industry, the method of surface disinfec- tion with UV light makes an important contribution wherever bacteria andvirusesneedtobeinactivatedinanenvironmentally-friendlymanner.
