Slide Set 6

Yeast Management

Priming and Bottling

Kegging

A little history

How yeast work

Improving fermentation

Yeast types and strains

History Reinheitsgebot (German Beer Purity Law of 1516) only

listed malt, hops, and water as allowed ingredients

In the 1850’s Louis Pasteur did research and published papers, describing the role of yeast in fermentation

Prior to that people knew about yeast and beer They knew the importance of transferring yeast from

batch to batch – just not its role

Around 1780, the Dutch packaged and sold a yeast slurry

Compressed yeast cakes entered the market about 1825

Some scientists thought fermentation was a chemical reaction and yeast were a byproduct

How Yeast Work Beer yeast consume sugars and produce CO2 and

alcohol as waste

Sugar Typical Range in Wort

Glucose 10% - 15%

Fructose 1% - 2%

Sucrose 1% - 2%

Maltose 50% - 60%

Maltotriose 15% - 20%

Dextrins 20% - 30% (non-fermentable)

Phases of Fermentation Adaptive (a few hours)

The cells adjust to environment (temperature and food)

Attenuative (a few days) High-growth phase and high-attenuation

Kräusen forms

Maturation / Conditioning (a few more days) Yeast slow and kräusen drops

Beer clears and flavor improves

Flocculation Yeast are tired and nearly out of food

Yeast clump together and fall to bottom

Other Compounds Produced Mainly produced during high-growth phase

Esters and other flavor compounds

Acetaldehyde

Diacytle

Some are cleaned up by the yeast

Improving Fermentation (Give the yeast what they need)

Cool wort to pitching temperature

Aerate to add O2 – yeast use O2 to chemically synthesize fatty-acids and sterols to build their cellular membranes (8 – 12 ppm O2 needed)

Pitch enough yeast

Add yeast nutrients, if needed

Free Amino Nitrogen (FAN) usually supplied by the barley malt

When a wort contains significant percentage of adjuncts, may need to add FAN

Aeration Data (5 gal. wort 1.040 to 1.080)

Method Time (min.)

O2 Level (ppm)

Siphon with sprayer -- 4

Shaking small volume with air 1 8

Shaking large volume with air 5 3

Airstone with aquarium pump 5 8

Airstone with O2 tank (1 L /min.)

1 2

9 14

Yeast Types Beer yeast come in two types (species)

Ale Yeast (Saccharomyces cerevisiae)

Lager Yeast (Saccharomyces pastorianus)

Genus = Saccharomyces

Species = cerevisiae and pastorianus

These two species are closely related but produce different beers, even with the same wort Ale Yeast: Top fermenting. Make fruity tasting esters.

Lager Yeast: Bottom fermenting. Leave few esters.

Wild yeast can be a completely different genus (e.g. Brettanomyces) – making a completely different beer.

Yeast Strains Strains within each species are more closely related

However, they act differently during fermentation Sometimes small differences in esters / aroma

Other times, the same wort can produce completely different beers depending on the yeast strain used

Hundreds of different strains of beer yeast are available to the brewer. Dry yeast verities are limited due to rigors of dehydration

More verities are available as liquid yeast

Most yeast packaging contain about 100 billion cells (sufficient for 5 gallons of 1.040 to 1.060 ale wort.)

Strain Characteristics Attenuation – wort dependent (given as an average)

Low (65% - 70%)

Medium (70% - 75%)

High (75% - 80%)

Flocculation Low – most of the yeast does not settle

High – most of the yeast settles

Medium – anything in between

Best fermentation temperature range

Esters, flavors, aromas

Reference vendor websites (e.g. Whitelabs)

Why this is important

Most recipes do not mention pitching rate

Pitching Rate For good fermentation using fresh yeast

For ales: 0.5 to 1 billion cells per liter (2 to 4 billion per gallon) per 4 gravity points For lagers: 1 to 1.5 billion cells per liter (4 to 5.5 billion per gallon) per 4 gravity points

For re-pitched yeast, double the number of cells.

Why are more needed or lagers?

Based on these numbers, one package of 100 billion cells can ferment 5 gallons of 1.040 wort

40/4 * 5 * 2 = 100 billion cells

Why these rates? The sheep analogy

100 sheep on 1 acre quickly eat the grass but no reproduction

10 sheep on 100 acres lots of reproduction but long time to consume all the grass

100 sheep on 10 acres all the grass eaten plus a predictable amount of reproduction

The balance between the rate of consumption of sugars and the amount of cell reproduction has a big impact on the character of beer.

Pitching Rate and Flavor During the high-growth phase, yeast produce more

aromatics and esters

They also produce more diacetyl precursors, fusel alcohols, and other off-flavor compounds

The yeast will clean theses up later in the fermentation (unless they go dormant)

Under stress (either feast or famine), yeast produce more short-chain fatty acids that need to be esterfied

The optimal rate is somewhat style dependent

Over Pitch or Under Pitch What is the effect of pitching too few cells?

It is a feast for the cells you pitch

More growth phase and amino acid production

More byproducts potential off-flavors

What is the effect of pitching too many cells? Moderate over pitch Less growth Less byproducts

Fewer esters bland flavor for some styles (too clean)

Extreme over pitch Famine More byproducts

It is more difficult to overpitch in the extreme than to under pitch err on pitching more cells

Dry Yeast Rehydration Manufacturers often say to sprinkle it over the wort.

The intent is to make it more convenient to use

Up to half the cells could die because they cannot draw in enough water due to the sugar concentration

Wait until wort is ready for pitching the yeast

Sprinkle yeast onto 1 cup of warm pre-boiled water (80oF for ale yeast and 72oF for lager yeast)

Cover and let stand for 15 minutes

Gently stir

Cover and let stand another 15 minutes

Yeast Starters More common when using liquid yeast due to cost

There are more varieties of liquid yeast

For dry yeast it is easier to rehydrate several packages

Determine pitching rate for beer (Tables 7.1 to 7.3)

Choose starter volume using growth factor (Table 7.4)

Make 1.040 SG starter wort

Needs to be well aerated

Add yeast and cover top with aluminum foil

24 to 48 hours for propagation

Decant off “beer”, chilling will help yeast settle

Example Palmer’s Glorious Abys – Black IPA (page 404)

Original Gravity = 1.070

Brew Volume = 6 gallons

From table 7.2, for 1.070 OG, pitch 32 to 65 billion cells per gallon

Need 32 * 6 = 192 to 65 *6 = 390 billion cells.

Around 300 billion should be good

From table 7.4, one yeast packet (100 billion cells) in a 3 liter starter will work

Recommended Procedure Equipment: Erlenmeyer Flask and Stir Plate

Steps Make a 1.040 SG wort

Boil for 10 minutes in the flask

Cool in the flask

Add yeast

Cover with foil (you want air)

Place on stir plate and set for a small vortex

Fermentation time 24 to 48 hours

Remove from stir plate and let yeast settle

Decant and discard “beer.” Pitch the yeast slurry that remains

• Review of priming and bottling

• How much sugar

• Forced carbonation and kegging

Priming & Bottling Review • Sanitize everything that contacts the beer • Measure an appropriate amount of priming sugar • Dissolve in 2 cups of water and bring to a boil

• Pour cooled sugar solution into the bottom of the bucket • Transfer beer to priming bucket with minimal splashing • The transfer should sufficiently mix the beer and sugar

• Install a section of tubing on the priming bucket valve to reach the bottom of a bottle

• Fill each bottle avoiding splashing • Cap each bottle • Wait one to two weeks for the beer to condition

How Much Sugar Carbonation is given in volumes (where 2.5 volumes

means that 2.5 liters of CO2, at standard temperature and pressure, is dissolved in 1 liter of beer).

In table 10.1, Palmer gives the amount of priming sugar needed for 2.5 volumes CO2 in 5 gallons of beer (70oF):

4.0 oz of cane/table sugar (sucrose)

or 4.7 oz of corn sugar (dextrose)

Table 10.2 gives the amount of table sugar (sucrose) per gallon needed for different carbonation levels at various temperatures.

How Much Priming Sugar? Example: How much sucrose (table sugar) is required

to have 3.0 volumes of CO2 in 3 gallons of beer, where the final fermentation temperature was 68oF?

Table 10.2 shows that 1.02 oz. of sucrose per gallon should be added.

Multiplying by 3 gallons gives 3.06 oz. as the amount.

Substitute dextrose (corn sugar) for the sucrose.

From table 10.1 the ratio of dextrose to sucrose is 4.7:4.0

Therefore, add 4.74.0 × 3.06 = 3.6 oz. of dextrose

Why Temperature Matters It has to do with the residual CO2 in the beer after

fermentation is finished and before bottling.

At 1 atmosphere of pressure and 70oF, beer can hold 0.8 volumes of CO2. Need to add 1.7 volumes to have 2.5 volumes total.

Colder beer can hold more CO2 at a given pressure.

No more CO2 is added after fermentation ends. If it warms after fermentation, it will loose CO2.

If it cools after fermentation, it does not gain CO2.

What matters is the highest temperature, after fermentation ends and before capping.

How Much Carbonation? The amount of carbonation depends on the style of

beer you are making. Style guides such as https://www.craftbeer.com/beer/beer-styles-guide give this information. Palmer lists some on page 159.

British Pale Ale: 1.5 to 2.0

American IPA: 2.0 to 2.5

German Hefeweizen: 2.5 to 3.0

You can always adjust carbonation to your own taste.

Don’t over do it. It can become difficult to pour into a glass or worse the bottles could explode!

• You can prime the keg with sugar like you do bottles but almost nobody does.

• Rather than bottle conditioning beer with priming sugar, it can be transferred to a keg and force carbonated

• Since force carbonation does not depend on working yeast, the beer can be filtered to clarify it.

• Forced carbonation is about the only option for very high alcohol beers.

Equipment Required for Kegging Keg

Kegs are readily available in 1.75, 2.5, 3 and 5 gallon sizes

Larger sizes can also be found

CO2 tank, regulator and fittings.

A 5 gallon kit is $225 from Williams Brewing

A 2.5 gallon kit is $195 from Williams Brewing

Used 5 gallon kegs are readily available for less

You will need space in a refrigerator.

5 gal. kit

2.5 gal. kit

Kegging Steps After fermentation is complete, transfer the beer to a

keg. The transfer tube should go to the bottom of the keg to avoid splashing and adding oxygen.

Seal the keg and place it in a refrigerator. Refrigeration is not required for carbonation, however, higher temperatures require higher pressures.

Connect the CO2 line from the regulator to the keg. Set the pressure to achieve desired carbonation level. Safe maximum for most kegs is 40 psi!

How to Determine Pressure There is an equation that calculates the carbonation in

volumes, given temperature and pressure. In table 10.4, Palmer gives carbonation levels for various combinations of temperature and pressure.

What pressure is needed for 2.5 volumes of carbonation?

Look for the various points in Table 10.4 for 2.5. You can use linear interpolation, if needed.

Temperature oF

Pressure psi

Comment

35 10

40 12.5 Interpolated

70 28.3 Interpolated

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