Bacterial Contaminations in bottled craft beers from Patagonia Andina.

MAILEN A. LATORRE; DIEGO LIBKIND

San Miguel de Tucumán

Simposio; V International Symposium on Lactic Acid Bacteria: Benefitting from Lactic Acid Bacteria progress in Health and food.; 2016

CERELA

Beer is considered a drink of low microbiological risk because it presents unfavorableconditions for microbial growth: it has ethanol, high carbon dioxide, low pH, reducedcontent of oxygen and sugars and antibacterial substances from hops (iso- α-acids).However, there are microorganisms able to tolerate these conditions and negativelyaffect their quality producing turbidity, acidity and unwanted aromas and flavors. This isthe main problem affecting the quality of the beers worldwide. Lactic acid bacteria,particularly Lactobacillus and Pediococcus genera, lead contamination incidentsreported in beer in Europe (60-90%), followed by strict anaerobes, enterobacteria andacetic acid bacteria. Little is known about the incidence of bacterial contaminantsaffecting micro-breweries in Andean Patagonia. We aim to determine the incidence ofbacterial contamination in bottled craft beers from Andean Patagonia. For this, 75 beersfrom different Patagonian localities were evaluated by sensorial, physico-chemical (pH,bitterness, color, turbidity and final density), and microbiological analyses. For the latter,beers were inoculated in media: Hsu's for Lactobacillus (Hsu?s) and Pediococcus (HLP)and Wallerstein Differential (WLD) for detecting lactic and acetic acid bacteria and someenterobacteria. In WLD, colony forming units (CFU) count was performed, thenrepresentative colonies were isolated and cryo-preserved for subsequent molecularidentification. Half of the beers studied showed evidence of microbial contamination,detected by the heightened perception of acidity and phenols. Not statisticallysignificant relationships were found between the measured physicochemical parametersand contamination events, however it was noted that most of the contaminated beerhad high turbidity and pH ≤4.2. Fifty seven percent of the samples recorded growth ofbacteria of which 74% were positive for the medium HLP, indicating the presence oflactic acid bacteria. Counts up to 10 7 CFU/ml of beer were obtained when suggestedvalues are ≤5 CFU/ml. Preliminary molecular identification of isolated bacteria detectedLactobacillus (Lactobacillaceae), Acetobacter (Acetobacteriaceae) and Klebsiella(Enterobacteriaceae). The remaining bacteria isolated in this study (60 strains) are in thestage of molecular identification and constitute the first culture collection of brewingcontaminants beer that will be helpful for the development of detection and controlstrategies for microbreweries.