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Biochemistry of Beer

By Dmitry Liskin Norfolk, VA October 2012. Biochemistry of Beer. According to Rheinheitsgebot (1516) beer should only contain: Water Barley Hops Yeast was discovered in 1800 by L. Pasteur. What is Beer?. Beer-like beverages appeared around 10,000 BC

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Biochemistry of Beer

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  1. By Dmitry Liskin Norfolk, VA October 2012 Biochemistry of Beer

  2. According to Rheinheitsgebot (1516) beer should only contain: • Water • Barley • Hops • Yeast was discovered in 1800 by L. Pasteur What is Beer?

  3. Beer-like beverages appeared around 10,000 BC First evidence points at Mesopotamia region Is said to be responsible for development of agriculture origin of beer

  4. Hardness • Carbonate – temporary • Gave birth to beers with malty, smooth finish • Munich, Dublin, London, St.Louis, Milwaukee • Sulfate – permanent • Bitter, pale beers • Burton-on-Trent • Other ions • zinc, copper are necessary for fermentation • Iron, manganese and chloride will cause flavor problems water

  5. Malt: barley that has been sprouted and dried • Color • Golden to black • Aroma • Bready, malty, nutty, toasty, roasty • Flavor • Caramel, toffee, molasses, coffee • These characteristics develop due to non-enzymatic browning reactions barley

  6. Thermal decomposition of sugar, pyrolysis • 110 oC – 180 oC • Low-moisture • Produces a variety of products Caramelization

  7. Reaction between amino acid and sugar • 48 oC – 230 oC Maillard reactions

  8. Beer preservation Bitterness Flavor Aroma hops

  9. Brewers’ best kept secret • Converts fermentable sugars to alcohol • Top fermenting – ale; bottom - lager • Contributes to flavor with other byproducts • Fusel alcohols • Esters • Aldehydes yeast

  10. Bitters and Pale ale Stout Scottish ale India Pale ale Lager Classic Beer styles

  11. The beer of an Empire (1702 – 1714) • Use of coal gave birth to pale malt • Firm hop bitterness • Low hop character • Touch of caramel from malt (bitters) • Light fruity character from yeast • About 5% alcohol Bitter and Pale Ale

  12. Dark beer with roastycharacter • Refreshing low alcohol to warming high gravity beers • Dry stout • Sweet stout • Oatmeal stout • Imperial stout Stout

  13. Malt sweetness, smoky Clean finish Low bitterness Wide range of alcohol levels 60/-, 70/- and 80/- Scottish ale

  14. Bitter, hoppy ale Crisp finish Malty, some caramel flavor Moderately strong (5% - 7.5% alcohol) India pale ale (IPA)

  15. Malt focused beers Low hop character 4.4% – 5.4% alcohol Clean finish Most food friendly style lager

  16. Base malt with specialty grains • Mashing • Hydration of malt • Gelatinization of starches • Release of natural enzymes • Conversion of starch to fermentable sugars Making of beer - mashing

  17. Starch conversion (60 oC – 75 oC) • Alpha-amylase • Beta-amylase • Limit-dextrinase • Alpha-glucosidase • Protein rest • Proteases • peptidases Enzymatic activity

  18. Beer clarity • The hot break – protein coagulation • The cold break – protein coagulation • Hop additions • Bitterness – 60-90 min • Hop flavor – 20 min • Hop aroma – 5 min or dryhopping Boiling the wort

  19. Alpha acids = Bitterness of beer • Humulone • Cohumulone • Adhumulone • Measured by IBU’s (International Bittering Unit) • 1 IBU = 1 mg alpha acid per 1 L Alpha acid isomerization

  20. Myrcene – pungent Humulene – delicate and refined Caryophyllene oxide – herbal/spicy Flavor and aroma compounds

  21. Beer is born when yeast is pitched • Yeast characteristics • Type – Lager, Ale, Weizen • Flavor – malty, fruity, woody, etc. • Attenuation – degree of fermentation • Temperature – impacts flavor • Flocculation – precipitation of yeast • Sugar, oxygen, nitrogen and minerals are needed fermentation

  22. Adaptation • High growth • Aerobic process • A few hours • Attenuation • Production of alcohol • Anaerobic process • Fermentation of simple sugars • 4 – 10 days • Conditioning • Conversion of byproducts to ethanol • Flocculation Yeast at work

  23. Diacetyl and pentadione – buttery flavor Acetaldehyde – green apple aroma and flavor Fusel alcohols – oxidation to esters; fruity aroma These byproducts will be metabolized during conditioning stage Yeast byproducts

  24. Water • Hardness affects mash pH and taste • Malt • Color, flavor, aroma and body • Hops • Preservation • Bitterness, flavor, aroma • Yeast • Alcohol, flavor, aroma, clarity • Combination of these factors gives the finished product • Complex flavors are desired while complicated ones to be avoided Finished product

  25. Referenced literature • Randy Mosher “Radical Brewing” • John Palmer “How to Brew” • Ray Daniels “Designing Great Beers” • JamilZainasheff and John Palmer “Brewing Classic Styles” • BYO “Brew Your Own” magazine • O’Connor Brewery • Christopher Newport University department of Molecular Biology and Chemistry • Fellow brewers acknowledgements

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