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?