1) Yeast is responsible for alcoholic fermentation by converting sugars to alcohol and carbon dioxide. There are two main types of brewing yeast - ale/wheat yeast (Saccharomyces cerevisiae) and lager yeast (Saccharomyces pastorianus). 2) Hops contribute bitterness, aroma, and flavor to beer. They contain alpha acids and essential oils that are extracted during the boiling process. Common hop varieties used for bitterness have higher alpha acid levels while aroma hops have lower levels. 3) The brewing process involves milling malted barley, mashing to convert starches to fermentable sugars, boiling the wort with hops, cooling and fermenting

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Pham Van Hung
School of Biotechnology
small animal which sips sugar through its snout, and
excretes alcohol from its gut and carbonic acid from its
urinary organ.
1866 - Louis Pasteur
• Yeast was responsible for alcoholic
fermentation.
1883 - Emil Christian Hansen
• Developed pure culture technique
• Isolated pure cultures of brewing yeasts
Two types of brewing yeasts: originally
classified on flocculation behavior
Top-fermenting
Ale Weiss
Top-fermenting
• Ale yeast
• Weiss yeast
Bottom-fermenting
• Lager yeast
Lager

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Ale and Weiss yeasts - Saccharomyces cerevisiae
• Polyploid and probably aneuploid.
• Non-mating
• Sporulates poorly and poor spore viability
Lager yeast - Saccharomyces pastorianus
• S. cerevisiae
• S. carlsbergensis
• S. uvarium
• Sporulates very poorly - poor spore viability
Ale and Weiss yeasts - Saccharomyces cerevisiae
• Ferments only above 18°C
• Has a strong influence on flavour
Lager yeast - Saccharomyces pastorianus
• Ferments at any temperature above freezing
• Ferments “clean” (small influence on flavour)
Conversion of sugar to alcohol using yeast.
Process that is important in anaerobic
conditions when there is no oxidative
phosphorylation to maintain the production of
ATP (Adenosine triphosphate) by glycolysis.
During fermentation, pyruvate is metabolised
to ethanol and carbon dioxide.
Special flavors and aromas of beers arise from minor biochemical reactions

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Rapid initiation of fermentation
High fermentation efficiency
High ethanol toleranceHigh ethanol tolerance
Desired flavor characteristics
High genetic stability
Range of alcohol production
It is usual to select strains of yeast for
brewing from yeasts already in
commercial use.
S b i i l l dSome breweries isolate, select and
maintain their yeast strains but others
engage specialist laboratories to
provide this service.
Can make a stock of your yeast.
In the average brewery, a large inoculum
of cells is used (ca 5-15 million cells/ml
of wort).
In each fermentation the cell density
increases three-to-four-fold.
Therefore, one-third to one-fourth of the
yeast crop of each fermentation is used
for inoculation of the next batch.
Spice of beer
• Provides aroma and
bitterness
F ilF il C bC bFamilyFamily CannabaceaeCannabaceae
Humulus – 2 (3) species
•• H. japonicus – Japanese hop
• H. lupulus – brewing hop

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HopsHops areare dioeciousdioecious viningvining
perennials,perennials, havinghaving extensiveextensive
stemstem structuresstructures::
•• AbovegroundAboveground stemsstems (bines)(bines) andand
leavesleaves dyingdying atat thethe endend ofof thetheleavesleaves dyingdying atat thethe endend ofof thethe
growinggrowing seasonseason inin mostmost areasareas..
•• BelowgroundBelowground stemsstems (rhizomes)(rhizomes) andand
rootsroots overwinteringoverwintering..
•• RhizomesRhizomes serveserve asas primaryprimary meansmeans
forfor vegetativevegetative ((clonalclonal)) propagationpropagation
ofof femalefemale plantsplants forfor commercialcommercial
productionproduction..
Yakima Valley, Washington
Yakima Valley, Washington Mature Female Hop inflorescence

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BractBract BracteoleBracteole
Rachis (“strig”)Rachis (“strig”)
Hop flower
• 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.
Mature Female Hop
inflorescence (“Cones”)
Composed of bracts and
b t l th t l t lbracteoles that completely cover
the minute pistillate flowers.
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.

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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
flowers.
Hopunion, Yakima, Washington

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Water : 11 -13%
Lupulin : 15 -21%
Polyphenol : 2,5 -6%
Protein : 15 – 21%
Cellulose : 12 -14%
Essential oils : 0,3 – 1%
Minerals : 5 – 8%
Others : 26 – 28%
Lupulin 16%
• Soft Resins 13%
Alpha Acids 8%
Beta Acids 4%
humulone lupulones
Other Soft Resins 1%
• Hard Resins 2%
• Essential Oils 1%
Hydrocarbons 0.75%
Oxidation Products 0.2%
Sulphur containing compounds 0.05%
Vegative Matter 84%
Linalool (spicy) Geraniol
Myrcene
There are two main hop types: bittering
and aroma.
• Bittering hops have higher concentrations of
alpha acids (5 9%) and are responsible for thealpha acids (5-9%), and are responsible for the
large majority of the bitter flavor of a beer.
• Aroma hops usually have a lower concentration
of alpha acids (~5%) and are the primary
contributors of hop aroma and (nonbitter) flavor.
The nonbitter flavor and aroma of hops come
from the essential oils.
The composition of hop essential oils can differ a lot
between varieties and between years in the same
variety.
About 250 components of essential oils have been
identified.
22 of these are known to have significant influence on
the flavor and aroma.
The three major components of the essential oil of hops
are myrcene, humulene, and caryophyllene, which
comprise about 60–80% of the oil for most hop
varieties.

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Beer is composed mostly of water.
Hardness and alkalinity are important
Low levels of contaminants, otherwise filtering
is necessary
Regions have water with different mineral
components, as a result, different regions were
originally better suited to making certain
types of beer, thus giving them a regional
character.
Water filtering
• Remove any unwanted contaminants
• Add salts to bring the profile into the range
you wanty
Soft water for light coloured beers
Hard water for stouts (dark beer)
• Water chemistry is responsible for the
unique beers that were developed in
different regions of the world
Stouts require very hard water
Pilseners (pale lager) require very soft water
Malt Mill
Mash Tun
Cereal
Cooker
Lauter Tun
FermentationBrink
Brew
Kettle
Hot Wort
Receiver
Wort
Cooler
Aeration
Lagering
Hops

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Malted barley and specialty grains are run through roller
mill and cracked open.
This grist is then carried by an auger to the mash tun.
Malted Barley
and
Specialty Grains
In the mash tun the grist is mixed with hot water to form a mash.
In the mash, enzymes that exist in the grain become active and
convert the starches to fermentable sugar.
The sugar rich liquid from the mash, called wort, is drained from
the mash tun.
These photos show the milled
Malted barley being mixed with
Warm water. The enzymes
Convert the starch to maltose and
The proteins to amino acids creating
What is known as sweet wort.
The sweet wort
is separted from
the spent barley
by a filtration step
known as
lautering. The
barley husks servebarley husks serve
as the primary
filtering material.
Here, the remaining
spent grains are
being removed from
the sweet wort
with this screen.

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Brewers' wort commonly has 8-14% total solids.
90-92% are carbohydrates: glucose, fructose, maltose,
lt t isucrose, maltotriose.
Nitrogenous compounds, such as, amino acids.
Vitamins: biotin, inositol, pantothenic acid, pyridoxine,
and thiamine are present in wort and utilized by Brewers'
yeast.
Phosphates,chlorides, sulfates and other anions are
present with the cations Na, K, Ca, Mg, Fe, Cu, and Zn.
15
20
v)
73% Fermentable
11.77
4.43
0
5
10
CHO(%w/v
Fermentable Non-fermentable
52.960
80
100
%w/v)
28.4
16.1
2.6
0
20
40
Percent(
Glucose FructoseMaltose Maltotriose
151
269
200
250
300
M
107
132
65
53
30
49
63
89
31
126
56
93
105110
17
68
0
50
100
150
PPM
Ala
Arg
Asp
Glu
Gly
His
Ile
Leu
Lys
Met
Phe
Pro
Thr
Tyr
Val
Asn
Gln
Ser
Not included: Cys (2 ppm) and Trp (50 ppm)

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The wort is drained from the mash tun and moved to the brew kettle.
In the brew kettle the wort is boiled and hops are added.
From the hops we can extract bitterness, which will help balance the
sweetness of the wort.
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
beer.
• Coagulates protein which is removed from later• Coagulates protein which is removed from later
stages; also may complex and remove solubilized
tannins.
• 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.
After boiling, the wort is transferred through a chiller.
While passing through the chiller the wort is instantly chilled to
the appropriate temperature for fermentation.
From the chiller, the wort moves into a temperature controlled
fermenter.
Yeast is added and fermentation begins. In fermentation the yeast
will ferment sugars in the wort and produce alcohol, carbon dioxide,
and other flavor compounds.

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Traditional Fermentation:
Open System
• Open top fermenters
protected by a blanket
of carbon dioxide
during fermentation.
• Typical of aleTypical 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
Cylindroconical systems: Cylindro-Conical base, and pressure systems.
Fusel or higher alcohols:
By-product of amino acid metabolism.
Levels are affected by yeast strain.
Spicy, wine-like, and alcoholic taste.p y, ,
Organic acids:
Formed from carbohydrate metabolism
Contribute to the sourness or acid taste (also
pH) of beer.
Esters:
By-product of lipid metabolism in a reaction
between an alcohol and intermediates of lipid
synthesis.
Usually impart a fruity character to the beer.
There are two types:
Acetate esters
ethyl acetate (solventy, fruity, sweet)
isoamyl acetate (banana,fruity, sweet)
phenethyl acetate (roses, honey, apple, sweet).
Fatty acid ester
ethyl caproate (apple, aniseed, sweet)
ethyl caprylate (apple, fruity, sweet)

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Diacetyl
Byproduct of amino acid metabolism.
Tastes like butter, butterscotch, and feels slick onTastes like butter, butterscotch, and feels slick on
the palate.
Pentadione
Similar to diacetyl.
Milder flavor similar to honey or butter.
Acetaldehyde
Intermediate of ethanol production.
It can form in autolysis of yeast during lagering if yeast is
in poor condition.
It can also form if post-fermentation beer is exposed to
air (oxygen).
Ethanol can be oxidized to acetaldehyde.
Acetoin
Formed from a secondary reaction of alcoholic
fermentation.
Pyruvate decarboxylase converts pyruvate to
acetaldehyde, which is then converted to ethanol and
CO2.
Pyruvate decarboxylase sometimes joins two
acetaldehyde molecules to form acetoin.
After fermentation the fermented wort, now called beer, is
transferred through a filter.
The filter removes various proteins, hop residue and yeast cells.
From the filter, the beer moves to the beer servers.
These are carbonating tanks, holding tanks and serving tanks.

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Conditioning
• Beer requires a period of
post-fermentation
conditioning.
• Flavors “mature” through
this conditioning periodthis conditioning period.
• If conditioning is done
“cold”, it is referred to as
‘lagering’.
• Carbonation usually also
associated with the
conditioning process.
Packaging: Bottling
• Often done at high rates.
• Beer condition improved if air is
excluded.
• Must proceed in a sanitary and
efficient manner.
•Also must avoid high temperatures.
Shepherd-Neame Brewery, Faversham, Kent, England
Packaging: Kegging
• Traditional kegs made
from wood.
• Modern kegs are stainless
steel, typically 15.5 US
llgallons.
• Maintained in cold
condition, or beer is flash
pasteurized.
• Dispensed with carbon
dioxide system.
Stoudt Brewery, Adamstown, Pennsylvania

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The mash tun is a vessel in which the milled malted barley is mixed with water
And the enzymes are allowed to degrade the starches and proteins into
Substrates that the yeast can utilize during fermentation
Strainer
Kindly provided by Tom Pugh and David Ryder of Miller Brewing Company
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•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

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Yeast growth
Alcohol and CO2
Flavor compounds
Large - 600,000 L
Kindly provided by Tom Pugh and David Ryder of Miller Brewing Company
Carbonation Off-flavor reduction
Kindly provided by Tom Pugh and David Ryder of Miller Brewing Company