Brewing and Fermenting

Brewing and Fermenting

1. Ingredients in Beer

   • Hops
     • Female flower cone (Humulus lupulus)
     • More than 80 varities
     • Resin
       • adds the bitterness
       • iso-a-acids
       • essential to balance sweetness of malt
     • Essential oils
       • Have aroma characteristics
       • provide, fruity, floral, spicy etc
   • Malt
     • refers to malted barely
     • malting is the controlled germination of cereals to activate enzymes used in the mashing process
     • There are a spectrum of malt types
       • Base malts
         • lager (pilsner), ale
         • Provide enzyme activity for the mash
       • Toasted malts
         • Vienna, amber
       • Darker malts
         • Brown, chocoloate
       • Speciality
         • crystal, caramel
     • Provides body, and sweetness
     • Fermentable sugars, e.g alcohol
     • Variety of flavours, e.g grainy, toasted etc
     • Other sources of fermentable sugars
       • Cereal Adjuncts
         • Rice e.g Budweiser, & Japanese largers
         • Corn e.g Stella
         • Cane sugar (sucrose)
         • Honey, maple syrup, molasses
         • Why use this? - Cost is cheaper, and to modify beer properties
   • Yeast
     • Single cell organisms
     • Eukaryotic cells in fungi kingdom
     • Ale (top fermenting) e.g Saccharomyces cerevisiae
     • Lager strains (bottom fermenting) e.g S. pastorianus
     • Modern Classification and species differentiation achieved by DNA fingerprinting
     • Different yeast strains important for yeast styles and flavour properties
       • Hop & aroma flavours
       • Malt charactertics
       • Yeast derived flavour e.g fruity esters, tartness (organic acids), spicy, peppery phenolics
   • Water
     • Alkalinity, pH, hardness, mineral ion all determine beer character and beer style
       • different mineral ions affect beer flavour accentuating either malt or bitterness
     • Affects conditions for biochemical reactions during brewing
     • Important for yeast nutrition and optimal fermentation performance, hence flavour quality

2. Barley

   • 2-rowed variety
     • Only central floret is fertile, hence 1 seed at each node
   • 6-rowed variety
     • All florets are fertile, hence 3 seeds at each node
   • Structure
     • Husk (hull)
       • protects the embryo
       • Important in wort seperation
     • Aleurone
       • Source of enzymes, produced in response to hormones from the growing embryo
     • Endosperm
       • the starch granules here in the form of fermentable sugars and amino acids
       • Composed of large + small starch granules
       • Cell walls within matrix holding the starch granules are composed of beta-glucans, some pentosans, and protein
     • Acrospire
       • The plant shoot
     • Microphyle

3. The Process

   • Malting
     • 1st) Steeping
       • activation of enzymes by steeping with water
         • increases moisture from11-12% to 42-44%
         • Grains swell
       • 1st Immersion
         • 6-16 hours to raise water content to 3-37%
       • 2nd) Immersion
         • 10-20 hours
       • Air Rest
         • 12-24 hours
         • Expose embryos to oxygen
         • Remove CO2
       • Chemical Process
         • Water enters through the grain, through the microphyle and distributes through the endosperm
           • The water activates the embryo which produces hormones that migrate to the aleurone
             • This stimulates production of enzymes
     • 2nd) Germinating
       • Barley spread in a germination box, this:
         • Dissipates CO2
         • Keeps temperature constant
         • Prevents roots from matting
       • The acrospire grows alongside of the kernel
         • Pre-existing enzymes are released and new enzymes are created in the aleurone layer. This modifies the endosperm for the acrospire's use
           • The enzymes break down the endosprems's protein/carb matrix into smaller carbs, aa's and lipids, also open up the starch reserves
             • Modification refers to the degree to which enzymes break down the starch granules
       • Length of the acrospire will be around 75-100%
       • A Maltster judges the degree of modification by the length of acrospire
     • 3rd) Klining
       • Drying reduces moisture content from 45% to 5%
       • Kills any microbes
       • Performed at low temperatures to minimise degradation of enzymes
       • Stops germination and kills embryo
       • Inhibits any ongoing enzyme activity
       • Diastatic Power: the amount of enzymatic starch conversion potential that a malt has
       • The acrospire and rootlets are knocked off by tumbling
       • Malts klined at different times/temp to develop different colours + flavours
     • Initial Steps
       • Barely cleaned, sized, viability measured, and N content determined

4. Biochemsitry of malting

   • Starch
     • Composed of Amylose and Amylopectin
     • Enzymes involved are: a-glucosidase, a-amylase, b-amylase
       • a-amylase is main degrading enzyme
         • Attacks at random in the middle of amylose and amylopectin
           • This releases maltose and maltotriose, and dextrins
             • Maltose is the main sugar found during mash
         • More thermostable than b-amylase
     • Gelatinisation
       • To achieve gelatinisation mashing includes a conversion stage at 65C for 1 h
       • Small granules gelatinase at a higher temp than large granules