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A Rational Approach To Yeast Strain Selection In Product Development



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.

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.



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A Rational Approach To Yeast Strain Selection In Product Development Presentation Transcript

  • 1. A rational approach to yeast strain selection in product development Bill Simpson Cara Technology, UK 2009 Convention October 1-4, 2009 La Quinta Resort & Club La 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
  • 5. The global situation
    • Global annual beer production is now about 1.7 x 10 11 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 acetate Ethyl butyrate Ethyl hexanoate Floral Grainy Grapefruit H 2 S Honey Indole Isoamyl acetate Isovaleric Leathery Malty Mercaptan 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 23 o 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 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?
      • 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? 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
  • 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 [email_address]