Czy warto badać piwo? Mikrobiologia piwa: szczepy piwne i ich znaczenie dla browarników

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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