BEER - Iowa State University

Introduction to
Robert S. Wallace
Department of Ecology, Evolution, and Organismal
Iowa State University
Ames, Iowa 50011
Introduction to
Alcoholic Beverages:
What is Beer?
• A fermented (alcoholic) beverage derived
from grains.
Flavorings are often added to balance
residual sweetness of unfermented sugars
and other polysaccharides; bitter flavors
used most.
The fermentation organism is typically a
yeast species within the genus
Most beers have natural or intentionally
added carbonation.
Origins of Beer
Earliest evidence for the deliberate production of
beer dates to at least 5,500 BCE in Sumeria.
Use of domesticated barley is evident from
impressions of grains in vessels
Original beers were likely spontaneously
fermented, and may have been derived by
soaking roasted barley cakes in water.
Beers that had finished fermenting likely had
sediment and floating debris; the clear liquid in
the middle was drunk through reeds – precursors
of our modern ‘straws’.
A Sumerian bas-relief sculpture depicting
the drinking beer from amphora-like vessels.
• Selection for attributes of “full”
heads that do not shatter, and
multiple fruits drove the
domestication process
• Different qualities selected for
various uses of the grain: e.g.
baking versus brewing.
•Palea and lemma remain in cleaned grains.
•These form the ‘husk’ that is desirable in barley
to form the filter bed during mashing and sparging.
Malting is the process of germinating viable seed to allow the
embryo to develop enzymes (amylases, and others) which are
capable of breaking-down stored carbohydrates, typically in
the form of starch, and then stopping this growth at a specific
stage of development through kilning.
The process begins by imbibing the seed with water to initiate
Germination under aerobic conditions continues until a
critical stage of development, when the process is rapidly
stopped by heating and drying the germinated seed.
Traditional malting techniques included carrying out this
process on the floors of special facilities, and processing the
germinating grains by hand.
Modern techniques involve bulk processing of grains in
specialized malthouses, most involving the use of automated
troughs or (Saladin) boxes in environmentally controlled
Floor Malting - DeWolf-Cosyns Malting, Brussels, Belgium
Adolph Coors Brewing Company, Golden, Colorado
Cargill Malting, Stevens Junction, Wisconsin
Malting: Filling
the Saladin Box
• Following imbibition of the
grain in the steeping tanks, the
grain is sent through pipes in a
grain-water slurry.
• The grains fill a long trough
which is kept under cool
temperatures and high humidity
which favors germination
• A series of automated augers
turn the grainbed during the
germination process to assure
uniformity and maintain aerobic
conditions for the sprouting
Saladin Box - Cargill Malting, Stevens Junction, Wisconsin
Adolph Coors Brewing Company, Golden, Colorado
Kilning of Malt - I
Once the critical stage of germination and embryo growth
has been achieved, the process needs to be abruptly
The germinated grain is transferred to a kilning box where
hot, dry air is passed through the grain bed, which kills the
embryo (without effecting the enzyme characteristics), and
dries the malt to an acceptable moisture content.
The malt is then cleaned of rootlets and other structures, and
prepared for packaging and shipment.
Extensive biochemical and physical assays determine the
malts brewing (or other) characteristics.
Specialized kilning of certain malt products under a range of
temperature and moisture conditions, for varying lengths of
time, produce ‘specialty’ malts that are widely used in
Cargill Malting, Stevens Junction, Wisconsin
Kilning of Malt - II
Kilning done with wet malt under closed conditions
results in “crystal” or “caramel” malt due to
thermal saccharification of starches.
“Roasting” or dry kilning of malt results in
‘darkening’ or ‘browning’ of the grains due to
Maillard reactions:
α-amino acids +
(colorless or pale)
(Maillard products)
(dark color)
Malt color is determined by kilning – Measured in degrees Lovibond
Melanoidins contribute to beer color…..
Other Grains Used in
A variety of grains other than barley are used in the
brewing process as adjunct grains. These typically do
not have the same enzymatic composition as barley, but
do provide alternative sources of fermentable
carbohydrates, along with a range of aromatic and other
flavor compounds.
Main Adjunct Grains:
Wheat – Triticum aestivum
Rice – Oryza sativa
Oats – Avena sativa
Rye – Secale cerale
Corn – Zea mays
Sorghum – Sorghum bicolor
Millet – Panicum milleaceum
Starch Conversion - Mashing
Necessary to activate enzymes produced by
grass embryos by re-hydrating crushed grains.
Temperature raised to optimum temperature to
enable enzymatic breakdown of starch into
component sugars.
Selection of temperature and duration of mash
will determine fermentability of the resulting wort.
Mashing also liberates medium molecular weight
proteins which contribute to mouthfeel and
heading characteristics.
Teak Mash Tuns – Shepherd-Neame Brewery, Faversham, Kent, England
Teak Mash Tun – Shepherd-Neame Brewery, Faversham, Kent, England
Mash Tun No. 1 – Fuller, Smith & Turner Brewery, Chiswick, London, England
Carbohydrate Components of Malt
• Poly 1,4 glucose, amylose (starch)
- straight chains
- simple, easily-digested by amylases
• Beta-glucans
- have both 1,4 and 1,3 bonds
- partially digestible with amylases
• Amylopectins
- branched starch molecules
- branching with 1,6 bonds typical
- partially fermentable
Mashing – Amylase Activity
Alpha Amylase (to = 158º F; 70º C)
…G-G G-G-G-G-G-G G-G G-G-G-G G-G-G-G G-G-G-G-G G-G
Beta Amylase (to = 140º F; 60º C)
…G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G G-G
Sweet Wort and Boiling
Following mashing of the grain, the solubilized
sugars and oligosaccharides in solution are run
off the grain bed to a boiling vessel (the “kettle”).
The “spent” grain bed is washed with hot (170º F
77º C) water in a process known as sparging to
dissolve residual sugars.
At this point, the sugar solution is termed ‘sweet
wort’ which is then boiled for an hour or more.
During the boiling process, hops are added and a
variety of chemical processes occur which result
in the liquid becoming bitter; thus it is now
termed ‘bitter wort’.
Hops – Humulus lupulus
(Family Cannabaceae)
Hops are dioecious vining perennials, having extensive
stem structures:
– Aboveground stems (bines) and leaves dying at the end of the
growing season in most areas.
Belowground stems (rhizomes) and roots overwintering.
Rhizomes serve as primary means for vegetative (clonal)
propagation of female plants for commercial production.
Desired product is the dried inflorescences (“strobiles” or
“cones”) of the female plant which have lupulin glands on
the bracts and bracteoles which subtend the minute
Male hop plants are used primarily for breeding purposes’
in some cases male hops are planted to assist in improving
yield (e.g. British varieties).
Female inflorescences (“burs”) continue development even
if flowers are not pollinated (wind).
The Hemp/Hop
• Related to the Elm (Ulmaceae),
Mulberry (Moraceae) and Stinging
Nettle (Urticaceae) families.
• Wind-pollinated.
• Family with 2 genera:
Cannabis – 1 (2) species.
C. sativa [hemp; marijuana]
Humulus – 2 (3) species
H. japonicus – Japanese hop
H. lupulus – brewing hop
Cannabis sativa L.
Hemp cultivar (male)
Humulus lupulus
Brewing hop – (female)
Yakima Valley, Washington
Yakima Valley, Washington
Female inflorescences
of Hops (“Cones”)
• Desired product is the dried
dried inflorescences
(“strobiles” or “cones”) of the
female plant which have lupulin
glands on the bracts and
bracteoles which subtend the
minute flowers.
• Male hop plants are used
primarily for breeding
purposes’ in some cases male
hops are planted to assist in
improving yield (e.g. British
• Female inflorescences
(“burs”) continue development
even if flowers are not
pollinated (wind).
Female hop
“Bur stage”
• Female inflorescences have
all pistillate flowers with stigmas
extending beyond bracts and
bracteoles. This is considered
the “bur stage”
• Stigmas are receptive to
windborne pollen at this stage.
•Female inflorescences (“burs”)
continue development even if
flowers are not pollinated
Mature Female
Hop inflorescence
• Composed of bracts and
bracteoles that completely
cover the minute pistillate
• Compound inflorescences
(groups of individual cones)
arise from axillary branches.
• Hops are ready to harvest
when the bracts and bracteoles
become papery and somewhat
dry. Lupulin production will
have achieved its maximum at
this stage.
Rachis (“strig”)
Hop Flowers
• Female flowers are found in
the axils of each bract.
• The ovaries are covered with
lupulin glands.
•If flowers are pollinated, the
fruit that develops will be thinwalled and will surround a
single seed.
•Unpollinated flowers will not
develop fully, and the entire
inflorescence may lack any
fertile seed.
Hop Picking:
• All picking was done by hand.
• Extremely labor intensive.
• Often carried out by migrant
or other seasonal workers.
• Paid for amount harvested.
Hop Harvest: High Trellis System
Grandview, Washington
Not Harvested
Hop Picking
• Mature hop inflorescences
(“cones”) are plucked from hop
bines using wire “fingers” which
are run against suspended
• Cones are moved on to
further cleaning operations.
•Leaf and stem material is then
chopped-up, and sent to waste
piles; this material is then
spread on fields as ‘green
 Traditional Methods:
‘Oast House’ – England – Typically coal fired.
Hop Kiln – United States – Typically wood fired.
Both relied on convection and slatted floors.
Fire risk was always high in these systems.
Hops baled using ‘pocket’ technique, or screw type press.
 Modern methods:
Forced hot air, perforated floor system, over moveable cloth mesh.
Careful monitoring of temperature and blower volume possible.
Dried at ca. 150°-155° F for 8 to 12+ hours with forced hot air.
Cooled without adding heat for ca. 1 hour at ambient temperature.
• Hops are considered ‘dry’ when the strig (rachis) becomes less pliable,
and nearly snaps when bent, usually around 9% MC.
 Experienced ‘hop dryer’ responsible for monitoring progress of drying
Hop Kiln:
Slotted metal floor
and net-like cloth
• Allows for high volume of hot
air to be blown underneath kiln
to pass through the bed of
drying hops.
• Cloth used to moved dried
hops off of kiln and onto ‘baling
floor’ following a period of
cooling and conditioning.
Kilning Hops:
Rapid and
careful drying
• Forced hot air (approx. 150O
to 155OF is pushed through bed
of wet hops for 8 to 12 hours.
• Water removed rapidly; hop
cones become “papery” and
somewhat brittle.
• Upon cooling hops recover
some moisture, and are allowed
to cool for a period of time.
• The hops are then “dropped”
off of the kiln, and prepared for
 Kilned hops allowed to cool; in some cases hops take up atmospheric
moisture during cooling which makes them less brittle.
 Hops from various parts of the kiln bed are mixed to assure uniform
overall moisture content.
 Dried, cooled hops are then transferred to baling area.
 Automated machines weigh 200 pound portions of dried hops which
pass into a hydraulic press apparatus; bales are then compressed
between pieces of burlap.
 Burlap pieces are sewn shut, and the bale labeled, weighed, checked
for moisture content and prepared for transport and cold storage.
Completion of
Hops Baling:
Burlap Cloth
• Compressed hops are then
sewn into a bag made from
burlap, a natural plant fiber
made from jute (Corchorus
capsularis; Tiliaceae).
• Once sewn shut, the weight is
checked and the bales are set
out to check moisture content.
• Physical quality of the hops is
then assessed using a ‘hop
tryer’ and a moisture meter.
• Once checked, the hop bales
are then moved to cold storage.
Hopunion, Yakima, Washington
Kettle Reactions - Boiling
Boiling accomplishes several positive processes for
the wort prior to fermentation:
• Sterilizes wort so that only desired fermentation
organism accomplishes the conversion of wort to
• Coagulates protein which is removed from later
stages; also may complex and remove solubilized
• Volatilizes undesirable compounds, e.g.
dimethylsulfides (DMS) which would contribute
negatively to aroma profile.
• Isomerizes hop-derived alpha acids to increase
solubility, and contribute to bitterness flavor profile.
Kettle Reactions - Boiling
• Female flowers are found in the axils of each bract.
• The ovaries are covered with lupulin glands.
•If flowers are pollinated, the fruit that develops will be
thin-walled and will surround a single seed.
•Unpollinated flowers will not develop fully, and the
entire inflorescence may lack any fertile seed.
“Copper” CW 2 – Fuller, Smith & Turner Brewery, Chiswick, London, England
Isomerization of Humulone
“Bittering Components”
α-acids – (humulones)
occurs during the
boiling process
(*both cis- and trans- forms)
Brewing Microbiology
Primary fermentation organisms are yeasts of genus
S. cerevisiae – ale strains; wine strains, baking strains
S. delbrückii – weizen beer strains
S. carlsbergensis (syn. S. uvarum) – lager strains
Highly diverse range of yeasts and bacteria reported from
spontaneous lambic beer fermentations:
Yeasts: Brettanomyces, Kloeckera, Saccharomyces;
Bacteria: Citrobacter, Enterobacter, Hafnia, Klebsiella,
Certain beer styles include fermentation with anaerobic
lactic fermentative organisms: e.g. Lactobacillus
Contaminant organisms (e.g. Pediococcus) found almost
ubiquitously in brewery settings; constant screening to
avoid spoilage.
Anaerobic Fermentation:
Sugars to CO2 and Ethanol
acid O O
dioxide O=C=O
Workhorses of
• Yeasts are unicellular
ascomycete fungi with no (or
sporadic) sexual stages.
• Reproduction occurs primarily
through asexual ‘budding’ or
clonal growth through simple
mitotic cell division.
• Capable of aerobic and
anaerobic metabolism.
Traditional Fermentation:
Open System
• Open top fermenters
protected by a blanket of
carbon dioxide during
• Typical of ale
fermentations which are
“top fermenting”.
• Sanitation is a primary
concern; contamination
risk is high.
• Modern systems utilize
closed fermentation.
Modern Fermentation – Closed systems
Redhook Brewery, Woodinville, Washington
• Beer requires a period of
• Flavors “mature” through
this conditioning period.
• If conditioning is done
“cold”, it is referred to as
• Carbonation usually also
associated with the
conditioning process.
Packaging: Bottling
• Often done at high rates.
• Beer condition improved if air is
• Must proceed in a sanitary and
efficient manner.
• Also must avoid high
Shepherd-Neame Brewery, Faversham, Kent, England
Packaging: Kegging
• Traditional kegs made
from wood.
• Modern kegs are stainless
steel, typically 15.5 US
• Maintained in cold
condition, or beer is flash
• Dispensed with carbon
dioxide system.
Stoudt Brewery, Adamstown, Pennsylvania
Beechwood Aging at Anheuser-Busch
“Evolution” of Beer Styles1
pure strain
S. delbruckii
wheat beers
lactic fermentation
Berliner Weisse
spontaneous fermentation
S. cerevisiae
roasted barley
dark malt
Belgian Lambics
Brown Ale
increasing hops & gravity
Pale Ale - ESB
S. carlsbergensis
+ hops
pale malt
+ malt
Dortmunder Export
Barley Wine
Belgian Ale
+ malt & sugar
India Pale Ale
+ corn
Trappist Ale
Cream Ale
from M. Jackson, 1988
Beer Summary
• Beer is among the oldest beverages made
by humans, and has persisted through
thousands of years of human development.
Both barley and hops require extensive
post-harvest processing before the plant
material becomes suitable for use in the
brewing industry.
Beer is a multi-faceted beverage with a rich,
intimate history involving plant
domestication, selection, and breeding.
Beer is one of the “universal” beverages
found in most societies around the world.