czy warto badać piwo? mikrobiologia piwa: szczepy piwne i...
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Nicholas A. Bokulich, and Charles W. Bamforth Microbiol. Mol. Biol. Rev. 2013;77:157-172
Microbiota of malting and brewing
2 categories of brewing yeast
Ale Yeast• “Top-fermenting” yeasts
• Saccharomyces cerevisiae strains
• Highly diversified
Lager Yeast• “Bottom-fermenting” yeast
• S. pastorianus: hybridization of S. cerevisiae with S. bayanus
• Carlsberg and Tuborg types
• Ability to metabolize melibiose
Consistent fermentation
Key variables:• Yeast quantity and health
• Oxygen input
• Wort nutritional status
• Temperature
• Yeast-wort contact (mixing)
Nicholas A. Bokulich, and Charles W. Bamforth Microbiol. Mol. Biol. Rev. 2013;77:157-172
Phylogeny of primary beer spoilage bacteria
Main Problem Areas:
• Packaging
• Raw Material
• Fermentation
• Finished Beer
Barley
• Plant-pathogenic fungi e.g Fusarium spp.
• Other fungal pathogens capable of producing mycotoxins e.g deoxynivalenol
(DON), nivalenol, T-2 toxin, HT-2 toxin, and diacetoxyscirpenol
• Fungal infections causing gushing
• Cause premature yeast flocculation (PYF)
• Inhibit germination
• Decreasing rootlet growth
• Decrease alpha-amylase activity
1. Steeping
2. Germination
3. Kilning
Malt
WortPros:
• Mash acidification (Homofermentative Lactic Acid Bacterium (LAB))
• Extraction
• Fermentability
• Nitrogen yield
• Foam stability, color, flavor of beer
Cons:
• Excessive acidification (Bacillus spp.)
• Nitrosamine
• High levels of butyric acid (Clostridium)
• Retard filtration
• Production of beta-glucanases and xylanases (lowering wort viscosity)
Beer
Gram-positive bacteria• Greatest threat:
• Lactobacillus brevis and Pediococcus damnosous
• LAB spoilage: • Acidification
• Haze formation
• Diacetyl production
• Exopolysaccharides (EPS)
Gram-negative bacteria• Greatest threat:
• Veillonellaceae organisms (Pectinatus, Megasphaera, Selenomonas, and Zymophilus)
• Growth at pH of ≥4.3 and with ≤5% (wt/vol) ethanol
• Beer spoilage:• Haze formation• Over production of propionic acid, acetic acid,
hydrogen sulfide, and mercaptans
• Zymomonas mobilis (tequila)• Growth at pH of >3.4 and ethanol contest of
<10% (wt/vol) and iso-alpha-acid resistant• Production of acetaldehyde and hydrogen sulfide
Wild yeasts
Saccharomyces cerevisiae• Ester production
• Phenolic off-flavors (POF)
• Haze formation or sediment
• Superattenuation
Non-Saccharomyces cerevisiae• Brettanomyces yeasts:
• High volatile phenolic compounds:• 4-ethylguaiacol and 4-ethylphenol
• Beta-glycosidaes activity
• Pichia anomala, Pichia fermentans, Pichia membranifaciens, etc. Candida tropicalis, Candida boidinii, Candida sake, Candida parapsilosis, etc. Kluyveromyces marxianus, Debaryomyces hansenii, Zygosaccharomyces bailii, Zygosaccharomycesbisporus, Schizosaccharomyces pombe, and Kloeckera apiculata
Biogenic Amines
• Formed by microbial decarboxylation of
amino acids
• Health hazard to sensitive individuals
• Formed primarily during fermentation
• LAB are most common producers of
biogenic amines
• Some Enterobacteria and
Saccharomyces may play a role in BA
formation
Packaging and Distribution • Kegs
• Briefly exposed to atmosphere
• Biofilms
• Prolonged exposer to warm temp. and air
• Packaged beer
• Pectinatus (Gram-negative bacteria)
• Fluctuations in temperature, light and/or turbulence
• Draft systems (coupler, lines, and tap faucet)
• Biofilms
• Spoilage through haze, off-flavors, and BA production
Czy warto badać piwo?
• General awareness of this phenomena due to microbiological
spoilages is fundamental to understanding the microbiology aspects
of the brewing process
• Rogue microorganisms do not only present potential threats but also
opportunities which can be applied in controlled conditions for
innovative brewing methods
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