Assessing microbial quality of beer heat treated by flash and tunnel pasteurization.

Beer is mainly produced through fermentation. This process happens in the presence of the only micro-organism that is allowed which is Saccharomyces cerevisiae which ferments the small sugars to produce alcohol, carbon dioxide and energy. A large percentage of microbial
contamination occurs when the yeast strains are introduced into the process. Beer is a high nutrient product that is susceptible to microbial contamination. Beer contamination is when microorganisms are present in the product. These microbes are classified as beer spoilage microorganisms, aerobic bacteria and wild yeast which have different effects on the quality of beer. Beer spoilage microorganisms are responsible for the staling of beer which is also a consequence of aerobic bacteria present in the beer. Presence of wild yeast in the beer always gives the beer a cloudy color and causes what is termed as haze. This microbial contamination is only able to be controlled through pasteurization which is the heat treatment of beer at the
end of beer production. There exist three (3) types of pasteurization across the globe. Tunnel pasteurization, flash pasteurization and sterilization. But in Zambia, only two (2) of these are used. Tunnel pasteurization and flash pasteurization are the main pasteurization processes that most macro and micro breweries use. Comparison of the effectiveness of flash and tunnel pasteurization was studied in this research. Twenty-four samples were collected and analysed. Different agars were used to inoculate these samples depending on the type of microbes that were needed to be identified in wort stage, fermentation stage and before and after the pasteurization samples. Biochemical tests were done to further identify the variety of microorganisms that were present. The micro-organisms associated with beer were identified, the various types of micro-organisms were also identified and the comparison between flash and tunnel was assessed through the microbial analysis and serial dilutions that were done. Results show that there were traces of beer spoilage bacteria and wild yeast. This contamination by microorganisms is a clear indication of insufficient/no cleaning of vessels. Recommendation is to implement CIPs of the dilution system of the brewery, CIPs of the BBTs to Filler to be started, hose management at filtration to be identified by developing an SOP for it.