Non-alcoholic beer has been named as a potential source of pathogens
The absence of alcohol in non-alcoholic or low-alcohol beers can make such varieties more vulnerable to bacteria and other spoilage factors during production, storage and bottling. This has been experimentally confirmed by American scientists.
Traditional beer, whose strength is usually 3.5-5% but can go as high as 10%, has a low pH level, contains ethanol, bitter hop acids, large amounts of dissolved carbon dioxide and little oxygen. All of this contributes to the microbiological stability of the beverage. Plus the classic beer-making process itself, which includes steps such as mashing, wort boiling, pasteurization, sterile filtration and cold storage, provides additional protection against foodborne pathogens.
However, when making so-called craft weak or non-alcoholic beers, producers often alter traditional processes. In addition, different ingredients, including non-sterile hops, may be added during fermentation and conditioning to improve the flavor and aroma of the beverage. This increases the risk of pathogenic microorganisms getting into such beer.
Specialists from Cornell University (USA) decided to understand how pH, storage temperatures and ethanol concentrations affect the growth or death of food pathogens in low-alcohol and non-alcoholic beer. Their study was published by the Journal of Food Protection.
For the experiment, the researchers purchased canned hoped beer from Genesse Brewery (Rochester, New York). Initially, its strength was less than 0.5% and its pH was 3.65. The beer was then used to make samples with different pH levels: 4.20, 4.60, and 4.80. The ethanol concentration was either kept the same or increased by adding alcohol to 3.20%.
The scientists added three foodborne pathogens to the samples: E. coli bacteria (E. coli O157:H7), Salmonella enterica and Listeria monocytogenes. The beer was then stored for 63 days at temperatures of 4 and 14 °C.
It was found that the pathogens survived and multiplied in the non-alcoholic beer. In samples with added E. coli O157:H7 and S. enterica bacteria, their numbers doubled after storage at 14 °C, but no growth was observed at 4 °C. The L. monocytogenes bacteria proved to be more sensitive: their concentration decreased rapidly and subsequently the pathogen was not detected in any of the tested samples.
The experiment showed that storage temperature is crucial for preventing pathogen growth. Mario Çobo, one of the authors of the paper, also noted that beer samples with a pH level higher than 4.60, little or no alcohol concentration and low carbon dioxide content were more susceptible to spoilage.
Given the pathogenic risks, the scientists recommended that food regulatory agencies evaluate the formulation of such soft drinks and test them more closely for safety.
"Low-alcohol and non-alcoholic beers should be pasteurized to achieve industrial sterility. Sterile filtration and the addition of preservatives should be considered as additional measures to reduce microbial risk," the researchers concluded.