Beer

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The Chemistry of BeerJim Enterkin LDM group Special Talk 5/22/09

Outline History Ingreedients Barley, Hops, Yeast, Water

Brewing process The processing, and what effects we expect them to have on properties of the final product

Beer characteristics The properties that we observe, and how they were derived from the processing of the ingredients

Conclusion & links for more info

History Beer is older than recorded history How and when it was discovered is unknown Evidence that barley was used for fermentation prior to the baking of bread Likely accidental discovery: Grain at some stage of germination immersed in water Wild airborne yeasts land in water Natural fermentation Some brave soul drinks this water Not only was it tasty, but it got him/her buzzed!!!!

History Beer is the reason for civilization as we know it Civilization depended upon nomads settling into villages Nutrition and longevity actually decreased as humans moved into farming villages Main reason to settle into villages was a steady supply of grain Why would the steady supply of grain be important enough to endure worse nutrition and shortened lifespan?

History Beer improved health and hygiene Especially in populated areas, water was often highly contaminated Beer is completely safe No organisms that are harmful to humans can survive in beer Combination of alcohol, pH, and CO2 content

History Ancient Babylon 4000 BC Sophisticated brewing techniques Beer integrated into religious ceremonies

2000 BC More than a dozen beer styles from various ingredients

Ancient Egypt Beer brewed, sold, and served exclusively by female brewsters Brewsters held high social status

History Middle Ages Beer as important as bread in diet Beer brewed in the home or in monasteries Monasteries advanced brewing techniques For the nutritional needs of monks and pilgrims Gained reputation for superior quality beer Sale of beer helped fund monasteries

Some communal brewhouses arise by late middle ages

History Colonial America Beer brewed mostly by women Beer brewed mostly in the home Brewing of beer in was a standard household activity, like baking bread

History Uniformity of lager beers Industrial Revolution Trains and refrigeration lead to mass produced and shipped beer

Prohibition and the depression lead to consolidation of the industry

History Revival of Beer 1971, England, CAMRA (CAMpaign for Real Ale) Cold War Americans stationed in Europe experience different styles of beer

1979, USA, legalization of homebrewing Today: Craft brews is the fastest growing segment of the beverage industry

History Louis Pasteur (1822 1895) Work in microbiology stemmed largely from desire to understand role of yeast in fermentation Disproved spontaneous generation Developed germ theory Pasteurization Anaerobic respiration

S. P. L. Sorenson (1868 - 1939) Developed pH scale for more accurate control of wort production (1909)

Outline History Ingreedients Barley, Hops, Yeast, Water

Brewing process The processing, and what effects we expect them to have on properties of the final product

Beer characteristics The properties that we observe, and how they were derived from the processing of the ingredients

Conclusion & links for more info

Types of Grain 2-row Barley Higher extract, less husk Preferred by craft brewers, home brewers, and European breweries

4-row Barley Used only as cattle feed

6-row Barley Preferred by large U.S. breweries Yields more amylases to help break down the cheap adjuncts (i.e. rice and corn)

Other Grains Wheat, Oats, Corn, Ricehttp://www.extension.umn.edu/distribution/cropsystems/components/7658-9.html

Malting Grain (usually barley) is malted Harvested grain is soaked in water until it germinates This activates amylases (and proteases)

Grain is dried This halts the conversion

Barley Amylase

Acrospires (sprouts) are removed Grain is cured usually at least one monthhttp://www.scientiaevitae.de/gb/2/5/beer.htm

Barley Modification Acrospires eat endosperm as they grow during malting Acrospire is the sprout, endosperm is its food source (full of starch) Acrospires will continue to eat endosperm until it is depleted or they are stopped by the maltster by heating and drying Longer acrospire growth leads to: More endosperm consumed and less fermentable sugar More amylases are activated More yeast nutrients released Clearer beer and more complete fermentation

http://www.scientiaevitae.de/gb/2/5/beer.htm

Malting Toasting or Roasting Varying heats hotter for darker malts Varying times Varying fire sources

Malt Germinated and crushed grain Amylases (and proteases) accessible but inactive Starches from endosperm partially broken down

Hops Used in continental Europe since 700s AD Introduced to Britain in 1500s by Flemish immigrants Didn t replace use of other herbs for over 200 years after Bog myrtle, horehound, alehoof, buckbean, wormwood

Hops Humulus lupulus (family = Cannabinaceae) Perennial vine Flowers of female plant grow into strobiles (cones) composed of leaflike bracts and bracteoles Bracteoles have lupulin glands Lupulin glands produce resins containing alpha acids These provide bitter flavor and act as a preservative Oils from the plant add flavor and aroma

Alpha Acids Humulone R = CH2CH(CH3)2 Cohumulone R = CH(CH3)2 Adhumulone R = CH(CH3)CH2CH3

Hops Bitter herb grown on a vine Alpha acids bitter taste and preservative Aromatic oils

Yeast The most mysterious ingredient for most of the history of beer, but also the most important Called God is good by medieval brewers as it turned wort into beer and produced more of itself It is unknown whether yeast or dogs were the first domestic animal

Yeast Through anaerobic respiration, it converts the malt sugar into alcohol, CO2, and other byproducts Often removed after fermentation, and can be re-uesd Yeast is essentially a fermentation catalyst The word enzyme (meaning biological catalyst) originates from the Greek for within the yeast **http://www.biotech.seagrant.org/glossary.html

Yeast 2 main types (for brewing purposes) Saccharomyces cerevisiae (ale yeast) Prefers warmer temperatures (20-25C) and will flocculate on top of the beer

Saccharomyces uvarum (lager yeast) Prefers cooler temperatures and will flocculate at the bottom of the beer (~5C)

Yeast Fermentation catalyst

Water 3 main concerns Flavor of water Nutrients for yeast Can t use distilled water

pH effects how well enzymes make maltose Keep mash pH 5-5.5

Ion concentration important e.g. Ca2+, Mg2+, CO32-

Darker malts lower pH more than lighter malts Areas with water with natural higher pH (e.g. Ireland) produced darker beers than areas with water with lower pH (e.g. Czech Republic)

Water The medium for fermentation

Outline History Ingreedients Barley, Hops, Yeast, Water

Brewing process The processing, and what effects we expect them to have on properties of the final product

Beer characteristics The properties that we observe, and how they were derived from the processing of the ingredients

Conclusion & links for more info

Brewing Process Sugar is extracted from grains Hops are added and wort is boiled Wort is cooled Yeast is added Wort ferments to become beer

Mashing & Lautering Mashing

Malt is soaked in hot water ~155F (~68C) Amylases re-activated starches broken down to sugars Primarily maltose = 2 glucose joined by (1 4) linkage

Proteins also broken down Processing of proteins and starches highly dependent on temperature pH also important for amylase activity

Lautering Grains are rinsed until water comes through clear Extract all ingredients into wort to be boiled

Boil Denatures and inactivates amylases Breakdown of starches halted Most proteins coagulate and settle out and can be removed Hot break

Extracts alpha acids and oils from hops Isomerizes alpha acids to isoalpha acids Kills any microbes in the wort Caramelization of sugars

Alpha Acid Isomerization

http://www.scielo.br/scielo.php?pid=S0100-40422000000100019&script=sci_arttext

Pitching Yeast Addition of yeast to allow fermentation Wort must be at proper temperature for yeast to survive and flourish Slightly off temperatures lead to off flavors Far off temperatures lead to stuck fermentation

Oxygen must be kept out Yeast only converts sugars to alcohol and CO2 under anaerobic respiration With oxygen present, aerobic respiration will dominate

Fermentation Yeast absorbs oxygen and sugar, and reproduces asexually When oxygen is used up, reproduction stops and fermentation (anaerobic respiration) begins Each glucose produces two molecules of ethyl alcohol and CO2 C6H12O6 2 CH3CH2OH + 2 CO2 + 118 kJ (2 ATP)

Large amounts of CO2 are produced and must be removed without letting oxygen in Airlock or water bubbler

Fermentation When all fermentable sugars have been consumed, fermentation stops and yeast begins to go dormant Yeast settle out and the beer clarifies This yields a young beer Bad taste and smell High concentrations of diacetyl and other organic byproducts

Conditioning Small amounts of remaining yeast continue to consume byproducts of initial fermentation Conditioning or aging, development of flavor

Packaging Flat beer is packaged (bottle or keg) and must be carbonated Add extra sugar for natural carbonation by fermentation Artificially carbonate from gas source

Outline History Ingreedients Barley, Hops, Yeast, Water

Brewing pro