A Rational Approach To Yeast Strain Selection In Product Development


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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

  1. 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. 2. Beer styles and brands – drivers of differentiation Yeast strains Product development
  3. 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. 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. 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. 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. 7. Important influences of yeast on beer composition Alcohol Apparent extract Real extract pH Colour Bitterness
  8. 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. 9. Important influences of yeast on brewing productivity Fermenter residence time Beer loss Alcohol yield Yeast growth
  10. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 24. Product development - target brand profile for a pale lager beer
  25. 25. Product development – process constraints for new pale lager beer
  26. 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. 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. 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