Process hygiene control in beer production and dispensing

Process hygiene plays a major role in the production of high quality beer. Knowledge of microorganisms found in the brewery environment and the control of microbial fouling are both essential in the prevention of microbial spoilage of beer. The present study examined the growth of surface-attached beer spoilage organisms and the detection and elimination of microbial biofilms. Moreover, the detection and characterisation of Lactobacillus lindneri, a fastidious contaminant, was studied. Beer spoilage microorganisms, such as lactic acid and acetic acid bacteria, enterobacteria and yeasts were shown to produce biofilm on process surface materials in conditions resembling those of the brewing process. However, attachment and biofilm formation were highly strain dependent. In addition, the substrates present in the growth environment had an important role in biofilm formation. Different surface materials used in the brewing process differed in their susceptibility to biofilm formation. PTFE (polytetrafluoroethylene), NBR (nitrile butyl rubber) and Viton were less susceptible to biofilm formation than stainless steel or EPDM (ethylene propylene diene monomer rubber). However, the susceptibility varied depending on the bacteria and the conditions used in the in vitro studies. Physical deterioration resulting in reduced cleanability was observed on the gasket materials with increasing age. DEAE (diethylaminoethyl) cellulose, one of the carrier materials used in immobilized yeast reactors for secondary fermentation, promoted faster attachment and growth of contaminating L. lindneri than ceramic glass beads. Beer dispensing systems in pubs and restaurants were found to be prone to biofouling, resulting eventually in microbial contamination of draught beer and cleanability problems of the dispensing equipment.