Presentation made to the 2009 Master Brewers Association of the Americas (MBAA) Convention, held 2 - 4 October 09 at the La Quinta Resort & Club in La Quinta, California, USA.

1. A rational approach to
yeast strain selection in
product development
Bill Simpson
Cara Technology, UK
2009 Convention2009 Convention
October 1-4, 2009October 1-4, 2009
La Quinta Resort & ClubLa Quinta Resort & Club
La Quinta, CaliforniaLa Quinta, California
Co-authors
Chris Giles
Hilary Flockhart
Craig Duckham

2. Beer styles and brands – drivers of
differentiation
Yeast strains
Product development

3. The birth of yeast
selection
Yeast ‘clones’ first applied commercially
in 1883
Prior to this yeasts were recycled from
one fermentation to another
Since then the number of yeast strains
used to make the world’s beer supply has
declined
An important source of product
differentiation has been undervalued

4. Frequency of DNA Fingerprint
types found in 83 commercial
lager yeasts
0
5
10
15
20
25
30
a b c d e f g h i j k l m n o p q r s t u v wx y
DNA fingerprint pattern
% yeast strains with this fingerprint type

5. The global situation
Global annual beer production is now
about 1.7 x 1011
litres
Market is made up of close to 70,000
brands from 12,000 breweries
There are about 2,500 mainstream
brands from 1,200 large breweries
How are these brands differentiated?
How important is choice of yeast strain
to that differentiation?

6. Drivers of
differentiation
Malt
Adjunct
Hops
Water
Salts
Oxygen
Yeast
Brewhouse practices
Fermentation practices
Maturation practices
End-processing practices
Packaging practices
Hygiene control
Oxygen control
Heat transfer control
Temperature / time control

7. Important influences of yeast
on beer composition
Alcohol
Apparent extract
Real extract
pH
Colour
Bitterness

8. Beer flavors whose levels
are increased or decreased
by yeast
Acetaldehyde
Acetic
Astringent
Bitter
Burnt rubber
Butyric
Caprylic
Caramel
Citrus
Diacetyl
DMS
Ethyl acetateEthyl butyrate
Ethyl hexanoate
Floral
Grainy
Grapefruit
H2S
Honey Indole
Isoamyl acetate
Isovaleric
Leathery
MaltyMercaptan
Metallic
Methional
‘Yeast bite’
Worty
Woody
Sweet
Solvent alcoholic
Smoky
Rotten vegetable
Phenolic (4-VG)
Musty

9. Important influences of yeast
on brewing productivity
Fermenter residence time
Beer loss
Alcohol yield
Yeast growth

10. Yeast taxonomy
Saccharomyces – Genus
Saccharomyces cerevisiae – Species (all
ale yeasts, including wheat beer yeasts)
Saccharomyces pastorianus – Species (all
lager yeasts) (old names include
‘Saccharomyces carlsbergensis’,
‘Saccharomcyes uvarum’,’Saccharomyces
cerevisiae’)

11. Lager brewing yeast
Saccharomyces pastorianus
Hybrid of Saccharomyces bayanus and
Saccharomyces cerevisiae
Most commercial strains are
taxonomically closely related to one
another
That doesn’t mean they make similar
beers

12. Ale brewing yeast
Saccharomyces cerevisiae
Commercial strains are taxonomically
very diverse
Wheat beer yeasts possess the PAD gene
that confers phenolic flavour compound
production

13. Pure yeast
 Pure cultures of lager yeast are in widespread
use today
 Compared to mixed strains, or strains which
contain a proportion of naturally-occurring
variants, pure yeast cultures give:
– Consistent beer flavor (both short term and long term)
– Consistent flavor stability
– Consistent fermentation behaviour (alcohol production, yeast
growth, fermentation times, diacetyl control, response to
problem malts)
– Consistent beer foam quality
– Consistent colloidal stability

14. Yeast collections
More than 1,000 brewing yeast
strains are available commercially
from a number of different public
and private collections
Possibly the largest collection of
commercial brewing yeasts in the
world is that established by Alfred
Jorgensen in 1891 - almost 700 yeast
strains (lager yeast, ale and wheat
beer yeasts)

15. AJL collection
Detailed fermentation and
process information is available
for about 200 of the strains
Strain key describes important
properties
 All information is held in
a database which allows
strains to be selected on
multi-variate criteria

16. Example yeast specification
Pure strain as determined by chromosomal DNA
analysis (100% purity)
Pure strain with respect to mutations in
mitochondrial DNA (>98% single colony type)
Fast fermentation rate
High alcohol yield with respect to sugar
utilized
Good osmotolerance - can handle worts of
23o
P+
Good beer flavor character

17. Example yeast specification
Good beer flavor stability
Not prone to attenuation problems
Appropriate flocculation behavior (not too
flocculent, not lacking flocculence; flocculates at
the right time – once fully attenuated (PE-LE of
0), allows cropping of at least twice the amount
of yeast pitched but does not grow excessively in
the fermenter
Total diacetyl at end ferment of <6.5 ppb/1%
alcohol vol/vol

18. Example yeast specification
Good alcohol tolerance (can tolerate up to 12%
vol/vol alcohol without undue cell damage)
Not sensitive to high glucose levels in wort
Able to perform well with low FAN concentrations
Not prone to autolysis problems
Easy to propagate using current equipment and
practices
High degree of genetic stability (no more than 5%
mutants after eight fermentations in the brewery)

19. Example yeast specification
Not prone to fobbing
Not sensitive to Premature Flocculation Factor
(PFF) from malt
Does not give rise to invisible haze problems in
the final product
Not genetically modified

20. Product maps can tell us what
people like
Overall
Like
StdV2 Br. A
Br. E
V4
Br. F
V5
V3
Br. C
V1
Br. D
Br. B
Each star represents
an individual’s
direction of
preference (going
through the centre
of the map).
From Greenhof & MacFie 1994
Statistical techniques are used to
place the beers in multi-
dimensional space, based on
differences in their flavor.

21. …. and why they like it?
Overall
Like
veg.
aroma
cabbage
like
soapy
bitter
hoppy
alcoholic
fragrant
fermenting
fruit
malty
toffee
sweet
body
citrus rancid
Br. E
V3
Br. C
V1
Br. D
Br. B
StdV2 Br. A
V5
V4
Br. F
drainy
Adding descriptive
profiling information
tells us why consumers
liked the products - they
generally liked the more
fully fermented ones.
From Greenhof & MacFie 1994
A highly trained flavor panel
provides the description.

22. Who likes what?
Overall
Like
Sulphury,
dirty
Fruity, Clean Bitter
Sweet
StdV2 Br. A
Br. E
V4Br. F
V5
V3
Br. C
V1
Br. D
Br. B
Differences in
preference can be
rationalized by
dividing consumers
into groups.
This is called
segmentation.
From Greenhof & MacFie 1994

23. Product development - target
brand profile for a pale lager
beer
0
1
2
3
4
5
Body
Bitter
Carbonation
Astringent
Sweet
DMS
Sour
After-bitter
Spicy kettle hop
Grainy
Isoamyl acetate
Malty
Solventalcoholic
Ethyl hexanoate

24. Product development - target
brand profile for a pale lager
beer

25. Product development –
process constraints for new
pale lager beer

26. Develop a detailed
understanding of
current brands and
processes
Develop a detailed
specification for the
new product
Identify changes needed to current
production process and bill of
materials to make the new product
Identify suitable yeast
strains for producing
the new product
Select the best
yeast strain in
laboratory trials
Propagate
yeast for
trials
Carry out brewery
trials – review -
revise
Production brews
Product development

27. Conclusions
We have limited options to differentiate
our products
Choice of yeast remains one of our best
differentiators (low cost, low risk, high
effect)
With more than 1,000 strains to choose
from brewers have significant
opportunities available to them
The challenge is in defining what is
needed and finding it – making the beer is
the easy part

28. Contact details
Cara Technology Limited
Leatherhead Enterprise Centre
Randalls Road
Leatherhead
Surrey
KT22 7RY
UK
Tel +44 1372 822218 Fax +44 1372 821599
www.cara-online.com bill.simpson@cara-online.com