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INTRODUCTION Recent advances have taken some of the mystery out of bacteria problems. Many mills that have been close to the allowed hygiene limits can now run with less worry about specs and potential costs. Board grades which are used for packaging of dry or fresh food milk or other liquids for human consumption have strict requirements regarding the hygienic quality of the packaging board. If they are not tightly controlled minute micro-organisms present in hygienic grades like liquid packaging board LPB or food-grade folding box board can be extremely costly. For example if part of a shipment of these grades is out of spec for hygiene the converter may reject the whole lot. A two-day outbreak of bacterial spores on a board making machine can lead to the loss of thousands of tons of finished LPB at a cost approaching millions of Euros. This is clearly a much bigger financial loss compared to for example a non-food grade machine where slime growth on machine surfaces means smaller losses in terms of downtime tonnage and money. To ensure that the hygienic quality of the final board meets the required BACTERIAL CONTROL MEASURES By Dr. Marko Kolari Senior Principal Scientist Microbiology Biotechnology RD and Technology EMEA Juha Rintala Marketing Manager Deposit Control Pulp Paper EMEA Kemira Oyj Finland WORLD PULPPAPER56 Better hygiene in food-packaging board at reduced risk of rejected tonnage and machine corrosion specifications manufacturers need to apply high-performance microbe control programs on their board machines. Over the past decade Kemira has emerged as one of the leading global suppliers of microbe control solutions to the hygienic board industry. Based on numerous RD programs and mill trials we now have a better understanding of how to control process conditions and avoid process situations that cause sporulation. Recent results with new applications in mills show that we are clearly on the right track in taking some of the mystery out of these frustrating and costly disturbances. This report summarises some of the things we have learned which can help you keep your board within the hygiene Many mills that have been close to the allowed hygiene limits can now run with less worry about specs and potential costs Figure 1. Microscope pictures of paper machine bacteria Cells of Deinococcus geothermalis growing on steel surface 1a and cells of Rubellimicrobium bacteria growing in process water 1b. These non-spore formers do not endanger hygiene of board as they are all killed by heat of dryer section. Fig 1c. A mature spore just being released from a Bacillus cell. If present in wet paper web these spores will survive alive into the dry finished board. B A C