P-37 - Characterization and Evaluation of the Microflora of Tunnel Pasteurizers in the Beverage Industry

Excessive growth of diverse microorganisms sometimes causes issues in tunnel pasteurizers used to treat beverages to provide either a long shelf life or safety in more sensible beverages. The present study aimed at evaluating the quantitative and qualitative aspects of this growth as well as evaluating the associated microbial load in the pasteurization stages, the surrounding air and the product itself. With the increasing market for non-alcoholic, low-alcoholic and alternative beverages being produced in breweries more and more products rely on heat treatment in the container for food safety. Albeit the process water being a rather barren niche considering the nutrients present, little to very excessive growth, up to flocks of biofilm blocking nozzles has been observed. The sampled machines cover a wide range of treated products as well as operating procedures. Culture media of the beverage and brewing industry as well as water analytics have been used alongside next generation sequencing methods to characterize the community and screen for possible beverage spoilers. Technical data and chemical analyses of the sampled machines was correlated with results to find strategies for optimal process strategies and factors of microbial load.

The microbial community is largely made up of bacteria with a minor fraction of yeasts and molds. The quantity of microorganisms was found to be between almost zero up to 10⁶/ml, high counts of microorganisms can also be found in the aerosol around the machine. No obligate beer spoilers have been identified but bacteria and yeasts that are known to spoil i.e. soft drinks.

Laboratory scale trials were used to assess the probability of the contaminated process water entering bottles closed with crown corks and swing tops to further evaluate the associated risk of microbial growth in tunnel pasteurizers for the product itself besides the spread by aerosol in the filling operation.

Different representatives of the spectrum of microorganisms found were trialed for their ability to grow and spoil or survive in regular beer, non-alcoholic beers of two makes, beer mix beverages as well as a soft drink. All the beverages showed robustness against the candidates with different microbial reduction rates being observed.

The combination of quantitative and qualitative data and operating strategies is used to deduct pointers towards an optimal operation of such machines and acts as the first reference of such kind to be published for use in the industry and to evaluate new methods and strategies towards a more sustainable production of food safe beverages.