Gram negative aerobic bacteria such as Acetic Acid Bacteria, which include Acetobacter and Gluconobacter, have historically caused significant problems to brewers. Although incidences of spoilage have recently reduced...Gram negative aerobic bacteria such as Acetic Acid Bacteria, which include Acetobacter and Gluconobacter, have historically caused significant problems to brewers. Although incidences of spoilage have recently reduced as a result of improvements in beer packaging, these bacteria are still a concern in dispense systems in pub breweries, public houses and cask conditioned beers. Gram negative facultative bacteria of the genus Zymomonas can spoil primed cask conditioned beer and cider. There is a wide range of Enterobacteraeceace which are found within brewery environments and they serve as indicator microorganisms for hygiene and sanitation. Gram negative strictly anaerobic bacteria such as Pectinatus and Megasphaera have recently emerged as a significant threat due to the improvement in reduction of oxygen levels in beer and an increase in production of unpasteurised beer. Pectinatus and Megasphaera are sensitive to routine cleaning agents used in breweries, but they can survive and proliferate in biofilms eventually causing spoilage of beer. This review focuses on Gram negative aerobic, facultative anaerobic and strictly anaerobic brewery related spoilage bacteria.展开更多
Brewer’s yeast strains are exposed to a spectrum of threats and“in-sults”thatcultures encounter during wort fermentation.Culture storage(including acid washing)andtheir propagation can also stress yeast systems.Str...Brewer’s yeast strains are exposed to a spectrum of threats and“in-sults”thatcultures encounter during wort fermentation.Culture storage(including acid washing)andtheir propagation can also stress yeast systems.Stresses are a plethora of parameters that ayeast culture toler-ates during its propagation,stprage,and throughout and between wortfermentations.Stress can result in a number of effects on a yeast cul-ture.These includedecreases in yeast viability and vitality,depletion of intracellular glycogen,increases intrehalose,and excretion of intra-cellular proteinase A and other proteinases,with effects onbeer foam stability.Shear of cell wall components will also occur.In addition,modification ofa culture’s flocculation characteristics can result,to-gether with the formation of unfilterablemannan-protein beer hazes,Finally,increases in respiratory deficient(petite)and other yeastmu-tants have been reported.展开更多
Premature yeast flocculation (PYF) has been shown to induce early and enhanced yeast flocculation and can result in a myriad of produc-tion difficulties and delays. Researchers have demonstrated that PYF is linked to ...Premature yeast flocculation (PYF) has been shown to induce early and enhanced yeast flocculation and can result in a myriad of produc-tion difficulties and delays. Researchers have demonstrated that PYF is linked to fungal infection of barley and/or malt. Therefore, one might suspect that PYF occurrence would increase in wet climates. To test this hypothesis, a control, a PYF-positive malt sample, and two Scot-tish-sourced malt varieties were compared with a control dataset of 77 femientations. Miniature fermentation trials using the ASBC method Yeast-14 were performed on these samples. Miniature fermentation tri-als have been optimized to detect PYF-causing malt by directly meas-uring attenuation via extract readings and indirectly measuring yeast in suspension via absorbance. Nonlinear and tilted Gaussian regressions were fit to the data sets to obtain attenuation and absorbance curves, respectively. Results obtained indicated that the PYF-causing malt in-duced both early and enhanced flocculation, whereas the other three malts (including the Scottish malts) did not induce early or enhanced flocculation. All four samples were compared using the F test, and it was determined that the PYF-positive malt sample was significantly different than the other three malts (P < 0.05). Using previous results from 77 miniature fermentation trials on control malts, a novel 95% prediction band was developed. This band was applied and used to identify and decisively confirm the presence of PYF-causing malt as demonstrated herein.展开更多
文摘Gram negative aerobic bacteria such as Acetic Acid Bacteria, which include Acetobacter and Gluconobacter, have historically caused significant problems to brewers. Although incidences of spoilage have recently reduced as a result of improvements in beer packaging, these bacteria are still a concern in dispense systems in pub breweries, public houses and cask conditioned beers. Gram negative facultative bacteria of the genus Zymomonas can spoil primed cask conditioned beer and cider. There is a wide range of Enterobacteraeceace which are found within brewery environments and they serve as indicator microorganisms for hygiene and sanitation. Gram negative strictly anaerobic bacteria such as Pectinatus and Megasphaera have recently emerged as a significant threat due to the improvement in reduction of oxygen levels in beer and an increase in production of unpasteurised beer. Pectinatus and Megasphaera are sensitive to routine cleaning agents used in breweries, but they can survive and proliferate in biofilms eventually causing spoilage of beer. This review focuses on Gram negative aerobic, facultative anaerobic and strictly anaerobic brewery related spoilage bacteria.
文摘Brewer’s yeast strains are exposed to a spectrum of threats and“in-sults”thatcultures encounter during wort fermentation.Culture storage(including acid washing)andtheir propagation can also stress yeast systems.Stresses are a plethora of parameters that ayeast culture toler-ates during its propagation,stprage,and throughout and between wortfermentations.Stress can result in a number of effects on a yeast cul-ture.These includedecreases in yeast viability and vitality,depletion of intracellular glycogen,increases intrehalose,and excretion of intra-cellular proteinase A and other proteinases,with effects onbeer foam stability.Shear of cell wall components will also occur.In addition,modification ofa culture’s flocculation characteristics can result,to-gether with the formation of unfilterablemannan-protein beer hazes,Finally,increases in respiratory deficient(petite)and other yeastmu-tants have been reported.
文摘Premature yeast flocculation (PYF) has been shown to induce early and enhanced yeast flocculation and can result in a myriad of produc-tion difficulties and delays. Researchers have demonstrated that PYF is linked to fungal infection of barley and/or malt. Therefore, one might suspect that PYF occurrence would increase in wet climates. To test this hypothesis, a control, a PYF-positive malt sample, and two Scot-tish-sourced malt varieties were compared with a control dataset of 77 femientations. Miniature fermentation trials using the ASBC method Yeast-14 were performed on these samples. Miniature fermentation tri-als have been optimized to detect PYF-causing malt by directly meas-uring attenuation via extract readings and indirectly measuring yeast in suspension via absorbance. Nonlinear and tilted Gaussian regressions were fit to the data sets to obtain attenuation and absorbance curves, respectively. Results obtained indicated that the PYF-causing malt in-duced both early and enhanced flocculation, whereas the other three malts (including the Scottish malts) did not induce early or enhanced flocculation. All four samples were compared using the F test, and it was determined that the PYF-positive malt sample was significantly different than the other three malts (P < 0.05). Using previous results from 77 miniature fermentation trials on control malts, a novel 95% prediction band was developed. This band was applied and used to identify and decisively confirm the presence of PYF-causing malt as demonstrated herein.
