Potential Paradigm Shift in a Tunnel Pasteurizer Water Treatment Program to Prevent Biofilm and Organic Deposition in Modern Brewery Pasteurizers

Abstract: For many years, the standard water treatment for controlling biological growth and organic deposits in pasteurizers involved using commercial Sodium Hypochlorite bleach (NaOCl) or bleach coupled with a bromine stabilizer in a defined ratio ranging from 10:1 to 20:1 of bleach to bromide. While this program produced acceptable results, it also presented several challenges. Issues with sodium hypochlorite residual control have adversely affected the lifespan of pasteurizer polypropylene mat top belts, caused periodic "medicinal" tastes in packaged beer, and led to equipment corrosion, among other recurring problems. This paper presents a new approach to controlling biological growth and preventing organic deposits in pasteurizers, which addresses many of the challenges associated with standalone bleach or bleach-bromide treatments. Data will be presented showing successful biological growth control in both water and vapor areas at previously unattainable low levels of free residual chlorine in the recirculating water compartments (regenerative zones). This new approach involves using sodium hypochlorite bleach coupled with a patented supplemental halogen stabilizer containing two specific biodispersants, replacing the previously used liquid sodium bromide for halogen stabilization. Unlike sodium bromide, this halogen stabilizer creates a chlorine “reservoir” in the recirculating pasteurizer water and converts a portion of the free chlorine residual to a more stable total chlorine residual. This more stable intermediate is less reactive with contaminants in the water, giving it more time to penetrate biofilm on system surfaces. The biodispersant component contains two surfactants specifically designed to remove and disperse the majority of biofilm and other organic materials, maintaining clean surfaces throughout the pasteurizer regenerative zones. The product is not a registered biocide, eliminating the complex process of permitting and registering a biocide for pasteurizer application. Another advantage is that the product can be periodically added to the pasteurizer regenerative zones, rather than continuously fed along with the bleach, to maintain specific free and total chlorine residuals. A state-of-the-art online biofilm monitor was used to record biofilm levels during a six-month trial period on a double-deck 12 oz bottle line pasteurizer with four regenerative and three pasteurization zones. Data will show that biofilm formation occurred during weekend offline periods when no chemical treatment was added, yet the biofilm monitor reading returned to a zero percent baseline within hours after the line was returned to weekday service. These initial results led us to lower the free residual setpoint to 0.5 ppm, where it remained throughout the trial period. When the stabilizer-dispersant feed was discontinued after the six-month trial period, biofilm readings initially increased. After the trial, bleach alone was fed until the free chlorine range was returned to original setpoints. No thermal or chemical boilout was needed during the trial period.