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ACETIC ACID BACTERIA DETECTION AS SPOILAGE MICROORGANISMS IN COMERCIAL GUARANA SOFT DRINKS

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Soft drinks are a single ecosystem, capable of inhibiting the multiplication of pathogenics and several spoilage microorganisms, because of the high acidity and the presence of preservatives. Because of these characteristics, the most important related spoilage microorganisms in soft drinks are yeasts and lactic acid bacteria. The damage caused by these microorganisms is slow, typically occurring four to six weeks after manufacture, at the distribution stage. Changes may be settling, flocculation, taste and odor strange and stuffing of containers due to carbon dioxide formation in fermentation. Aiming at exploring a valued niche in the state of Rio de Janeiro, guarana soft drinks samples were analyzed to detect and quantify the presence of bacteria and preservative resistante yeasts (PRY). PRY analysis was performed by the pour plate method, inoculating 1 ml of sample in TGE medium (tryptone, glucose, yeast extract) supplemented with 0.5% glacial acetic acid, incubating at 30 ° C / 72 hours. The analysis of the bacteria was carried out by the pour plate method and overlay, if inoculating 1 ml of the beverage in MRS medium (DeMan, Rogosa and Sharpe) and incubated at 35 ° C / 5 days. Three brands (A, B, C) are chosen in their normal and diet versions. For each drink, three separate batches, in triplicate, were tested for yeast and bacteria. Samples from brand A showed bacterial growth on the order of 102 CFU / mL in a standard version and a low-calorie. Bacterial caracterization (biochemical tests and Gram staining) showed that bacteria belong the acetic acid bacteria (AAB) group, genus Acetobacter.