WelcomeIntroduction to Yeast

Kara Taylor

What we will do today

• We will dispel some myths

• We will add to your information on yeast

• We will create discussion on yeast and fermentation

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What we will NOT do today

• We will not tell you step by step how to treat every yeast and fermentation issue

• We will not tell you “this is the only way to do…”

• We will not stop saying ‘it depends’

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What we HOPE to do todayWe hope to INSPIRE you to:

• pay attention to yeast needs

• test yeast, fermentation, and beer more

• experiment with new ideas and protocols

• create new beers

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Saccharomyces cerevisiae • One of the oldest domesticated organisms

– Used for brewing beer in Sumeria and Babylonia around 6000 BC

• Saccharomyces = sugar fungus; cerevisiae = Roman God of crops – Ceres

• Used as a eukaryotic model organism– Unicellular, doesn’t need a lot of room to grow,

eukaryotic can be applicable to humans– 1st genome to ever be sequenced in 1996

Yeast Used in BrewingAll yeast used in brewing worldwide is non-GMO

Ale Yeast• Original brewing strain -

Saccharomyces cerevisiae• Top ferment• Warmer fermentation temps• Wide strain variety

Lager Yeast• Natural hybrid -

*Saccharomyces pastorianus(Saccharomyces carlsbergensis)

• Bottom ferment• Colder fermentation temps• Limited strain variety

Other Strains• Saccharomyces uvarum• Saccharomyces bayanus• Saccharomyces eubayanus

*Saccharomyces pastorianus = Saccharomyces cerevisiae + Saccharomyces eubayanus.

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• Asexual reproduction by budding• Little to no sporulation• Therefore mating is rare• Polyploid• Phenol Flavor Negative• Stress tolerant• Flocculate• Hundreds of different, stable strains currently used

industrially

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Unique Properties of Brewers Yeast

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The ‘Real’ Significance of Yeast:Flavor

Glycerol

Glycerol

NAD+

Fig 2.3 Yeast: The Practical Guide to Beer Fermentation, White and Zainasheff 2010

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Why are Strains so Important:Flavor

• Alcohol

• Higher (fusel ) alcohols

• Esters

• Diacetyl

• Sulfur

• Acetaldehyde

• Phenolic compounds

*Different Yeast strains make different amountsDifferent Beers often require different yeast strains

In the beginning……

• Laboratories for commercial yeast did not exist

• Brewing strains were created by brewers by:– Continuing to use strains that

performed well and tasted good

– Passing strains to brewer to brewer

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The Beginning of Yeast Banking

• Emil Christian Hansen 1883– Developed pure culture

techniques• Strain selection and strain storage

The future of yeast banking

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• Founded in 1995- in San Diego• Chris was studying his Ph. D at UCSD

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New location in San Diego in 2011

More locations around the world

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Asheville, NC Copenhagen

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Yeast is Our Main Focus

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Yeast LabThe beginning stages of our propagation

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Step 1: Initial Culture Storage

• Freezes - critical• Plates/slants• Working plates

Yeast must be stored properly for a long, long time

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Step 2: Working agar plates/slants

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Step 3: Transferring to liquid media

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Step 3-5: Step-up Transfers

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Our Yeast Production Process

Controlling Fermentations

• What can you do to help your fermentations?– Healthy yeast – Temperature control– Good aeration – Good sanitation– Take some data points!

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Healthy Yeast

• We want good viability! (>80% alive)• Starter or no starter? • Keep yeast in fridge 2-4C • No freezing!

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Making A Starter

• Add 1 Purepitch to 1L of 8-10P boiled wort. • 24 - 48 hours on a stir plate. • 48 hours with no stir plate. • Refrigerate if not using it immediately

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Temperature Control

• Pick an appropriate yeast strain for what you can achieve

• Invest in temperature control supplies • Watch temperature the first 72 hours• Keeping it cool will help prevent many off

flavors

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Aeration

Yeast need at least 8-13ppm of oxygen in the wort

How do I ensure this in my homebrew? - Use an aeration stone for at least 60sec per

20L- Shaking is usually not enough!

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Methods for OxygenationHomebrewers

Fish Pump: Inserting a sanitized fish pump to a carboy can be a viable option for aeration. A sterile filter pictured here needs to be used. Typically aerating for 5-10 minutes

Shaking: A beginner’s method of aerating 20L carboy is to shake the carboy for several minutes. The amount of dissolved oxygen will depend on the amount of headspace in the carboy

Splashing: A method for beginners on a budget. Attached to the end of the hose filling the carboy.

Aeration Stone: Attach the stone to an oxygen tank. 60 seconds for 5gal (20L) is typically sufficient for homebrewing

Sanitation

• Cleanliness is important! • Clean, Sanitize, Sterilize

– Soap/Detergent Scrub– Caustic Soak– Acid Soak

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Cleaning & SanitizingCleaning is necessary to sanitize

something

Difficult to keep things sanitized when you brew outside

- Avoid air drafts - Change sanitizer buckets often - Make sure you’re using the correct amounts of chemicals and temperatures

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Monitoring pH

• Monitoring the pH of your wort can help predict the outcome of the fermentation– Reduction in pH = fermentation is happening – Reduction of pH too low = possible contamination

issues. Typically below < 3.0

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Yeast Collection & Harvesting

Stratification of yeast during collection

Beer

Healthy yeast

Trub and dead yeast

Smaller Scale

BEER

GOOD YEASTDEAD YEAST/ TRUB

1) Harvest yeast

2) Add sterile water and swirl

BEER/WATER

TRUB/DEAD YEAST

GOOD YEAST

POUR OFF

Acid Washing- To do or not to do?

• Acid washing only reduces bacteria

• Harsh on the yeast - typically reduces viability and performance

• Will not reduce wild yeast

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Protocol - Keep yeast at 2-4C- Add food grade

phosphoric acid until yeast is at 2.0-2.5 pH

- Mix for 60-90 minutes

- Add to fermentor(cold)

DIACETYL

glucoseglucose pyruvate

acetolactate

acetolactate

diacetyl

diacetylacetoin

2,3-butanediol

pHtemperature

valine

NADH2

NAD+

acetoin

2,3-butanediol

Forced Diacetyl Testing• Forcing conversion of precursor to diacetyl with heat

and oxygen– 2 samples

• Heated (water bath at140-160°F)• Room temperature

Procedure:• 10-20 minutes• Cool• Smell

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Forced Diacetyl TestingResults

Room Temp Beer Heated Beer Conclusion

Negative Negative Little to no precursor present, beer is ready to go

Negative Positive Precursor present, beer needs more time on yeast

Positive Positive Beer is loaded with precursor or possibly contaminated

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Thank you

Questions?

Kara@whitelabs.com