Jason Pratt
NHC 2015
Tips for Homebrewing
Lagers
Topics Covered
• Optimizing your Mash
• Prevention of Spoilage
• Yeast Strain Matters
• Propagation
• Impact of Oxygen
• Importance of Fermentation Temp
• Understanding esters
• Controlling Diacetyl
• Proper Yeast Handling
• Lagering / Aging
3
Tip #1: Optimize your mash
regime for the style • Factors to consider during Mashing:
• Time
– Enzyme action is increased with increased time.
• Temperature
– Each enzyme group has its optimum range. For
example, conversion temperature on the lower
side of conversion temperature will produce
worts with higher fermentability (lower EOF
Ratio).
• pH
– Each enzyme has its optimum temperature
range.
• Density
– Enzyme groups work more effectively with
different mash concentrations. For example,
amylases favor thinning mashes and protease
enzymes tend to work more effectively in thicker
mashes.
5
100
tem
p C0
75
50
25
Transfer to Lauter Tun
Mash Kettle
Mash Mixing Vessel
50
76
time in hours
TEMPERATURE/TIME MASH PROFILE
TREBLE DECOCTION MASHING WITH A MASH KETTLE
100
0 1 2 3 4
45
66
After mashing in a portion of mash (usually about 1/3)
is taken out of the mash mixing vessel and boiled in
a separate Mash Kettle. It is then added back to the
bulk of the mash to raise their combined temperature
for the next temperature stand. This process can be
repeated upto three times for the treble decoction mash
Proteoysis activity in mash mixing vessel
Saccharification activity in mash mixing vessel
Figure reproduced fromIndustrial Enzymology 2nd Edit ion by Godfrey & West Chapter 2.6 by Tim O'Rourke
Tip #1: Optimize your mash
regime for the style
Tip #2: Cleanliness is next to godliness
• Proper cleaning and sanitation is key to a
healthy lager fermentation
• Contamination by bacteria or wild yeast
competes for the nutrients and produces
undesirable flavors
• The usual suspects:
– Lactobacillus sp.
– Pediococcus sp.
– Wild Yeast
Tip #2 Cleanliness is next to godliness
• Lactobacillus sp.: – Rod shaped bacteria
– Sensitive to hop resins
– Common Off Flavors:
• Sour
• Diacetyl
• Pediococcus sp.
– Round shaped bacteria
– Sensitive to hop resins
– Common Off Flavors:
• Ropy turbidity
• Diacetyl
• Sour
• Wild Yeast: – Number of different species
– Common Off Flavors
• Over Phenols
• Fusel alcohols
• Over-attenuation
Tip #3: Your Yeast Strain Matters
• Understanding your yeast strain is of the utmost
importance
Factors effecting Yeast performance
– Yeast strain employed, and its viability
– Concentration of ions
– Fermentation Temp
– Pitch Rate
– Yeast tolerance to pressures
– Gravity of the wort
– Oxygen level at pitching
– Wort sugar composition
– Yeast flocculation characteristics
Tip #4: Keep the Yeast Happy in
Propagation • The prime objective of yeast
propagation is to produce the most yeast biomass in good physiological condition in the shortest period of time.
• Beyond the primary objective of supplying adequate healthy yeast are the requirements: – Yeast fit to ferment consistently
from batch to batch.
– Keep the culture genetically stable
– To keep the culture free of contamination by other microorganisms.
Tip #4: Keep the Yeast Happy
Propagation Practical tips and tricks:
• Always in propagate in wort that is
close to the target wort
• Best if the wort is within 1-2oP
• Propagate within a few degrees of
fermentation temperature
• Provide enough headspace for good
mass oxygen transfer while stirring
• Transfer to a new prop or into
fermentation when the gravity is
between 6-8oP
Tip #5: Temperature Matters
• The ideal temperature for
lager fermentation is
between 8 – 15oC
• Adjusting fermentation
temperature can have major
effects on yeast metabolism
and beer flavor
Tip #5: Temperature Matters
Temp Esters
Temp Fusel Alcohols
Temp Organic Acids
Temp Ferm Rate
Impact of Increasing Fermentation Temp
Tip #6: Understanding your esters is key
• There are over yeast derived 90 esters in beer
• The strain used has a signature ester profile
Gravity Esters
Ferm Temp Esters
Oxygen Esters
Pitch Rate Esters
Impact of Increasing Fermentation
Parameters on Ester Production
Tip #6: Understanding your esters is key
Practical Measures to Control Esters
– Supply wort with a suitable C:N
ratio and adequate supply of O2
to promote yeast growth, but
minimize ester synthesis
– Applying top pressure reduces
yeast growth and ester synthesis
due to an increase in intracellular
CO2 and decrease in intracellular
pH that disrupts enzyme function
– Keep zinc levels in check-
Increased levels of zinc increase
acetate esters of higher alcohols
due to the increase in precursors
Tip #7: Oxygen levels impact fermentation
performance
• Provide yeast with oxygen required for the
synthesis of sterols and unsaturated fatty
acids used by the yeast in cell membrane
synthesis.
• Target oxygen levels = 8-18 ppm
• Rapidly consumed in the first 6 hours of
fermentation
• Timing of pitching dramatically affects availability
of oxygen to the yeast.
Tip #7: Oxygenation levels impact
fermentation performance
Oxygen Fusel Alcohols
Oxygen Fatty Acids
Oxygen Esters
Oxygen Sulfurs
Oxygen Yeast
Impact of Increasing Oxygenation
Tip #8: Controlling diacetyl formation
• Diacetyl in Beer
Chemical reaction
dependent on
Temp & pH
GlucoseGlucose
in wortPyruvate
alpha-acetolactate
alpha-acetolactate
DiacetylDiacetyl
Acetoin
Acetoin
2,3 Butanediol
2,3 Butanediol
Amino Acid
Valine
Yeast Beer
Tip #8: Controlling diacetyl formation
Practical Tips and Tricks: – Optimize fermentation so that
diacetyl is produced as early as
possible • Proper FAN levels
• Proper wort oxygenation, better reduction
• Warmer temperatures, speedier reduction
• Increased yeast in suspension, faster
reduction
• Lower pH, speedier reduction
Tip #9 Proper yeast handling is vital
• The bottom of a fermenter is a hostile
environment for yeast due to the following: • High cell densities, which result in a corresponding increase in
metabolic heat being generated.
• Limited nutrients.
• High ethanol concentrations.
• Poor or no temperature control.
• High osmotic and carbon dioxide effects due to hydrostatic
pressure.
Tip #9 Proper yeast handling is vital
Practical Yeast Storage:
• Keep it cold
• Keep storage times low
• Dilute to get below 6% ABV
• Do not repitch yeast from
poor fermentations
• Acid Washing
• Minimize the exposure to O2
– Importance of glycogen for
repitched yeast
Tip #10: Lagering / Aging
At the end of fermentation three
principal flavor faults can remain:
– Acetaldehyde- bruised apple
– Diacetyl - butterscotch
– Sulfur compounds- burnt match
Goals for Lagering / Aging
• Flavor improvement and removal of
unwanted volatiles
• Oxygen control
• Beer sedimentation and clarification
• Beer stabilization
Tip #10: Lagering / Aging
• Process can vary:
• Some beers, yeast is fully
removed and CO2 is used to
purge the tank to remove
volatiles
• Some beers, yeast is carried
over and the temp is
dropped slowly
Questions?