Distribution of Bacterial Contaminants in a South African Lager Brewery

Abstract

Bacteria isolated from contaminated pitching yeast, fermenting wort and beer samples from a South African lager brewery over a one‐year period were tentatively identified by an improved, rapid diagnostic procedure as pediococci (41%), homofermentative lactobacilli (5%), heterofermentative lactobacilli (9%), Acetobacter spp. (7%), Gluconobacter spp. (13%) and Hafnia protea (25%). Pediococci and lactobacilli dominated samples taken from fermentation, storage and ‘bright’ beer tanks but were absent from pitched wort samples, from collection vessels and the single pitching yeast sample investigated. Acetic acid bacteria and H. protea were widely distributed in collection vessel, fermentation and storage tank samples, and H. protea was isolated from recycled pitching yeast.

125thAnniversary Review: Bacteria in brewing: The good, the bad and the ugly

“…Van Vuuren et al . also found that samples from fermentation and storages tanks were occasionally contaminated with Acetobacter and Gluconobacter . Furthermore, Ingledew reported an increased incidence of acetic acid bacterial spoilage in draught beer kegs.…”

“…Ploss and co-workers (101) found that these contaminants were only found in samples from the filling and filtration processes of the brewery, with 70% of the contamination belonging to A. pasteurianis sub pasteurianis. Van Vuuren et al (102) also found that samples from fermentation and storages tanks were occasionally contaminated with Acetobacter and Gluconobacter. Furthermore, Ingledew (99) reported an increased incidence of acetic acid bacterial spoilage in draught beer kegs.…”

Gram-negative spoilage bacteria in brewing

“…Frequent incidents of beer spoilage in draught beer kegs have been reported (Ingledew, 1979). Acetobacter and Glucono bacter have also occasionally been found in samples from beer fermentation and storage tanks (van Vuuren, Loos, Louw, & Meisel, 1979). AAB are still prevalent in cask-conditioned and barrel-aged beers (Bokulich, Bamforth, & Mills, 2012) (Table 8.2).…”

Review: Gram Negative Bacteria in Brewing

“…Frequent incidents of beer spoilage in draught beer kegs have been reported [24]. Acetobacter and Gluconobacter have also been occasionally found in samples from beer fermentation and storage tanks [39]. AAB are still prevalent in cask conditioned and barrel aged beers [40].…”