Beer Fermentations

Largest beer production by…

China

Which country drinks the most beer?

Czech Republic

History of Beer

• Safer than water

• Beer jar contained pale yellow residue - oxalate ion

Ales

• Top-fermenting yeasts

• Warm temp (faster ferm)

• Saccharomyces cerevisiae

Lagers

• Bottom-fermenting yeasts

• Fermented cold (slow fermentation)

• Saccharomyces pastorianus

Wild Brewing (Lambic styles)

• Open top fermentations, spontaneous

• Use wild yeasts

• High (uncontrolled) alcohol

• Sweet/fruity

• Seasonal fruits/herbs

Ingredients Needed

• Water

• Grains

• Hops

• Yeast

Beer Process: Malting

• Put barley in water, then remove.

• incubate cold and humid

• germinate - generates rootless

  • induces various hydrolases

• Dry germinated barley to preserve it… w/o losing enzymatic activity

  • Decreased moisture consumption

Beer process: Mashing

• Milling dried barley

  • Goal: to release the fermentable sugars into a liquid

    • Need enzymes to work on locked up substrates to release monomers (or dimer) and a.a. into liquid

• Heating

  • Heating malt/water mix slowly in stages

  • From lower to higher temps

    • Assortment of enzymes have an assortment of temp. optima

  • Mian starch degrading enzymes: alpha-amylases and beta-amylases

  • Pigments/flavors etc. are also extracted

• Kettle Boil - raise temp to 75 ℃, inactivating enzymes, denatures (some) proteins

  • Stuff precipitates, soluble fraction has fermentable in it, filter away precipitates

• Wort: 75% small fermentable sugars (glc, fru, mal, suc, etc.), 25% larger non-fermentable oligosaccharides (DP 4 and larger) —> prebiotics for humans. nitrgoen: 3-6% proteins/peptides/amino acids

• Reduce large substrates (starch and protein base units), making food for yeast

Adding Hops (Homolus lupulus)

Add flavor and aroma

• Flavor —> bitter due to hop alpha-acids

• Aroma —> hop oils (terpenoids, esters ketones)

• Add hops to kettle boil

Fermentation by Saccharomyces

Ale

• Saccharomyces cerevisiae

Lager

• Saccharomyces pastorianus

Fernentation occurs by Crabtree effect (lots of O2 around but still ferments

Glucose consumed first, catabolite repression blocks others from being consumed

Vegemite/Marmite

Made from yeast waste

Flocculation by Saccharomyces

Yeasts clump together and settle

• Clarifies the beer

• Allows for easier filtration

Wild Yeasts

• Brettanomyces is a non-spore forming genus of yeast (family Saccharomycetaceae). The genus name Dekkera.

• Used for long-term fermentations (months/years) after initial fermentation by Saccharomyces

• Funky flavors and aromas (barnyard and horse-blanket)

• Only used in brewers making specific ‘Brett’ beers

• If not wanting Brett, then major infection - “Burn it down”

Beer Spoilage

LAB

• Acidification, exopolysaccharide, diacetyl

AAB

HOP resistance in LAB

HOPs are antimicrobial

• Most common LAB resistant:

  • Pediococcus damnosus

  • Lactobacillus brevis

    • Transport hops out to keep themselves alive

• Hop-sensitive LAB

• Hop-resistance LAB