Introduction to Alcoholic Beverages Robert S. Wallace Department of Ecology, Evolution, and Organismal Biology Iowa State University Ames, Iowa 50011 Introduction to Alcoholic Beverages: Beer What is Beer? • A fermented (alcoholic) beverage derived • • • from grains. Flavorings are often added to balance residual sweetness of unfermented sugars and other polysaccharides; bitter flavors used most. The fermentation organism is typically a yeast species within the genus Saccharomyces. Most beers have natural or intentionally added carbonation. Origins of Beer • • • • Earliest evidence for the deliberate production of beer dates to at least 5,500 BCE in Sumeria. Use of domesticated barley is evident from impressions of grains in vessels Original beers were likely spontaneously fermented, and may have been derived by soaking roasted barley cakes in water. Beers that had finished fermenting likely had sediment and floating debris; the clear liquid in the middle was drunk through reeds – precursors of our modern ‘straws’. A Sumerian bas-relief sculpture depicting the drinking beer from amphora-like vessels. • Selection for attributes of “full” heads that do not shatter, and multiple fruits drove the domestication process • Different qualities selected for various uses of the grain: e.g. baking versus brewing. 6-row 2-row •Palea and lemma remain in cleaned grains. •These form the ‘husk’ that is desirable in barley to form the filter bed during mashing and sparging. Malting • • • • • Malting is the process of germinating viable seed to allow the embryo to develop enzymes (amylases, and others) which are capable of breaking-down stored carbohydrates, typically in the form of starch, and then stopping this growth at a specific stage of development through kilning. The process begins by imbibing the seed with water to initiate germination. Germination under aerobic conditions continues until a critical stage of development, when the process is rapidly stopped by heating and drying the germinated seed. Traditional malting techniques included carrying out this process on the floors of special facilities, and processing the germinating grains by hand. Modern techniques involve bulk processing of grains in specialized malthouses, most involving the use of automated troughs or (Saladin) boxes in environmentally controlled conditions. Floor Malting - DeWolf-Cosyns Malting, Brussels, Belgium Adolph Coors Brewing Company, Golden, Colorado Cargill Malting, Stevens Junction, Wisconsin Malting: Filling the Saladin Box • Following imbibition of the grain in the steeping tanks, the grain is sent through pipes in a grain-water slurry. • The grains fill a long trough which is kept under cool temperatures and high humidity which favors germination condition. • A series of automated augers turn the grainbed during the germination process to assure uniformity and maintain aerobic conditions for the sprouting grains. Saladin Box - Cargill Malting, Stevens Junction, Wisconsin Adolph Coors Brewing Company, Golden, Colorado Kilning of Malt - I • • • • • Once the critical stage of germination and embryo growth has been achieved, the process needs to be abruptly stopped. The germinated grain is transferred to a kilning box where hot, dry air is passed through the grain bed, which kills the embryo (without effecting the enzyme characteristics), and dries the malt to an acceptable moisture content. The malt is then cleaned of rootlets and other structures, and prepared for packaging and shipment. Extensive biochemical and physical assays determine the malts brewing (or other) characteristics. Specialized kilning of certain malt products under a range of temperature and moisture conditions, for varying lengths of time, produce ‘specialty’ malts that are widely used in brewing. Cargill Malting, Stevens Junction, Wisconsin Kilning of Malt - II • • Kilning done with wet malt under closed conditions results in “crystal” or “caramel” malt due to thermal saccharification of starches. “Roasting” or dry kilning of malt results in ‘darkening’ or ‘browning’ of the grains due to Maillard reactions: α-amino acids + sugars (colorless or pale) [O2] heat (Maillard products) melanoidins (dark color) Malt color is determined by kilning – Measured in degrees Lovibond Melanoidins contribute to beer color….. Other Grains Used in Brewing • • A variety of grains other than barley are used in the brewing process as adjunct grains. These typically do not have the same enzymatic composition as barley, but do provide alternative sources of fermentable carbohydrates, along with a range of aromatic and other flavor compounds. Main Adjunct Grains: Wheat – Triticum aestivum Rice – Oryza sativa Oats – Avena sativa Rye – Secale cerale Corn – Zea mays Sorghum – Sorghum bicolor Millet – Panicum milleaceum Starch Conversion - Mashing • • • • Necessary to activate enzymes produced by grass embryos by re-hydrating crushed grains. Temperature raised to optimum temperature to enable enzymatic breakdown of starch into component sugars. Selection of temperature and duration of mash will determine fermentability of the resulting wort. Mashing also liberates medium molecular weight proteins which contribute to mouthfeel and heading characteristics. Teak Mash Tuns – Shepherd-Neame Brewery, Faversham, Kent, England Teak Mash Tun – Shepherd-Neame Brewery, Faversham, Kent, England Mash Tun No. 1 – Fuller, Smith & Turner Brewery, Chiswick, London, England Carbohydrate Components of Malt • Poly 1,4 glucose, amylose (starch) - straight chains - simple, easily-digested by amylases • Beta-glucans - have both 1,4 and 1,3 bonds - partially digestible with amylases • Amylopectins - branched starch molecules - branching with 1,6 bonds typical - partially fermentable Mashing – Amylase Activity Alpha Amylase (to = 158º F; 70º C) …G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G …G-G G-G-G-G-G-G G-G G-G-G-G G-G-G-G G-G-G-G-G G-G Beta Amylase (to = 140º F; 60º C) …G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G …G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G G-G …G-G-G-G-G-G-G-G-G-G-G-G-G-G-G G-G G-G G-G G-G G-G Sweet Wort and Boiling • • • • Following mashing of the grain, the solubilized sugars and oligosaccharides in solution are run off the grain bed to a boiling vessel (the “kettle”). The “spent” grain bed is washed with hot (170º F 77º C) water in a process known as sparging to dissolve residual sugars. At this point, the sugar solution is termed ‘sweet wort’ which is then boiled for an hour or more. During the boiling process, hops are added and a variety of chemical processes occur which result in the liquid becoming bitter; thus it is now termed ‘bitter wort’. Hops – Humulus lupulus (Family Cannabaceae) • Hops are dioecious vining perennials, having extensive stem structures: – Aboveground stems (bines) and leaves dying at the end of the – • • • growing season in most areas. Belowground stems (rhizomes) and roots overwintering. Rhizomes serve as primary means for vegetative (clonal) propagation of female plants for commercial production. Desired product is the dried inflorescences (“strobiles” or “cones”) of the female plant which have lupulin glands on the bracts and bracteoles which subtend the minute flowers. Male hop plants are used primarily for breeding purposes’ in some cases male hops are planted to assist in improving yield (e.g. British varieties). Female inflorescences (“burs”) continue development even if flowers are not pollinated (wind). Cannabaceae: The Hemp/Hop Family • Related to the Elm (Ulmaceae), Mulberry (Moraceae) and Stinging Nettle (Urticaceae) families. • Wind-pollinated. • Family with 2 genera: Cannabis – 1 (2) species. C. sativa [hemp; marijuana] Humulus – 2 (3) species H. japonicus – Japanese hop H. lupulus – brewing hop Cannabis sativa L. Hemp cultivar (male) Humulus lupulus Brewing hop – (female) Yakima Valley, Washington Yakima Valley, Washington Female inflorescences of Hops (“Cones”) • Desired product is the dried dried inflorescences (“strobiles” or “cones”) of the female plant which have lupulin glands on the bracts and bracteoles which subtend the minute flowers. • Male hop plants are used primarily for breeding purposes’ in some cases male hops are planted to assist in improving yield (e.g. British varieties). • Female inflorescences (“burs”) continue development even if flowers are not pollinated (wind). Female hop Inflorescences: “Bur stage” • Female inflorescences have all pistillate flowers with stigmas extending beyond bracts and bracteoles. This is considered the “bur stage” • Stigmas are receptive to windborne pollen at this stage. •Female inflorescences (“burs”) continue development even if flowers are not pollinated (wind). Mature Female Hop inflorescence • Composed of bracts and bracteoles that completely cover the minute pistillate flowers. • Compound inflorescences (groups of individual cones) arise from axillary branches. • Hops are ready to harvest when the bracts and bracteoles become papery and somewhat dry. Lupulin production will have achieved its maximum at this stage. Bract Bracteole Rachis (“strig”) Hop Flowers • Female flowers are found in the axils of each bract. • The ovaries are covered with lupulin glands. •If flowers are pollinated, the fruit that develops will be thinwalled and will surround a single seed. •Unpollinated flowers will not develop fully, and the entire inflorescence may lack any fertile seed. Hop Picking: Traditional Methods • All picking was done by hand. • Extremely labor intensive. • Often carried out by migrant or other seasonal workers. • Paid for amount harvested. Hop Harvest: High Trellis System Harvested Grandview, Washington Not Harvested Mechanical Hop Picking • Mature hop inflorescences (“cones”) are plucked from hop bines using wire “fingers” which are run against suspended bines. • Cones are moved on to further cleaning operations. •Leaf and stem material is then chopped-up, and sent to waste piles; this material is then spread on fields as ‘green manure”. Kilning Traditional Methods: ‘Oast House’ – England – Typically coal fired. Hop Kiln – United States – Typically wood fired. Both relied on convection and slatted floors. Fire risk was always high in these systems. Hops baled using ‘pocket’ technique, or screw type press. Modern methods: Forced hot air, perforated floor system, over moveable cloth mesh. Careful monitoring of temperature and blower volume possible. Dried at ca. 150°-155° F for 8 to 12+ hours with forced hot air. Cooled without adding heat for ca. 1 hour at ambient temperature. • Hops are considered ‘dry’ when the strig (rachis) becomes less pliable, and nearly snaps when bent, usually around 9% MC. Experienced ‘hop dryer’ responsible for monitoring progress of drying operation. Hop Kiln: Slotted metal floor and net-like cloth covering. • Allows for high volume of hot air to be blown underneath kiln to pass through the bed of drying hops. • Cloth used to moved dried hops off of kiln and onto ‘baling floor’ following a period of cooling and conditioning. Kilning Hops: Rapid and careful drying • Forced hot air (approx. 150O to 155OF is pushed through bed of wet hops for 8 to 12 hours. • Water removed rapidly; hop cones become “papery” and somewhat brittle. • Upon cooling hops recover some moisture, and are allowed to cool for a period of time. • The hops are then “dropped” off of the kiln, and prepared for baling. Baling Kilned hops allowed to cool; in some cases hops take up atmospheric moisture during cooling which makes them less brittle. Hops from various parts of the kiln bed are mixed to assure uniform overall moisture content. Dried, cooled hops are then transferred to baling area. Automated machines weigh 200 pound portions of dried hops which pass into a hydraulic press apparatus; bales are then compressed between pieces of burlap. Burlap pieces are sewn shut, and the bale labeled, weighed, checked for moisture content and prepared for transport and cold storage. Completion of Hops Baling: Burlap Cloth • Compressed hops are then sewn into a bag made from burlap, a natural plant fiber made from jute (Corchorus capsularis; Tiliaceae). • Once sewn shut, the weight is checked and the bales are set out to check moisture content. • Physical quality of the hops is then assessed using a ‘hop tryer’ and a moisture meter. • Once checked, the hop bales are then moved to cold storage. Hopunion, Yakima, Washington Kettle Reactions - Boiling Boiling accomplishes several positive processes for the wort prior to fermentation: • Sterilizes wort so that only desired fermentation organism accomplishes the conversion of wort to beer. • Coagulates protein which is removed from later stages; also may complex and remove solubilized tannins. • Volatilizes undesirable compounds, e.g. dimethylsulfides (DMS) which would contribute negatively to aroma profile. • Isomerizes hop-derived alpha acids to increase solubility, and contribute to bitterness flavor profile. Kettle Reactions - Boiling • Female flowers are found in the axils of each bract. • The ovaries are covered with lupulin glands. •If flowers are pollinated, the fruit that develops will be thin-walled and will surround a single seed. •Unpollinated flowers will not develop fully, and the entire inflorescence may lack any fertile seed. “Copper” CW 2 – Fuller, Smith & Turner Brewery, Chiswick, London, England Isomerization of Humulone OH O R “Bittering Components” HO HO O O H α-acids – (humulones) HO O Isomerization occurs during the boiling process * * R OH iso-α-acids (*both cis- and trans- forms) Brewing Microbiology • • • • Primary fermentation organisms are yeasts of genus Saccharomyces: S. cerevisiae – ale strains; wine strains, baking strains S. delbrückii – weizen beer strains S. carlsbergensis (syn. S. uvarum) – lager strains Highly diverse range of yeasts and bacteria reported from spontaneous lambic beer fermentations: Yeasts: Brettanomyces, Kloeckera, Saccharomyces; Bacteria: Citrobacter, Enterobacter, Hafnia, Klebsiella, Pediococcus. Certain beer styles include fermentation with anaerobic lactic fermentative organisms: e.g. Lactobacillus Contaminant organisms (e.g. Pediococcus) found almost ubiquitously in brewery settings; constant screening to avoid spoilage. Anaerobic Fermentation: Sugars to CO2 and Ethanol CH2OH H C C HOH HO C H O OH H C OH C H glucose 2X pyruvic acid O O H3C-C-C-OH carbon dioxide O=C=O + H3C-CH2-OH ethanol H3C-CH=O acetaldehyde Workhorses of Brewing Fermentation: Yeasts. • Yeasts are unicellular ascomycete fungi with no (or sporadic) sexual stages. • Reproduction occurs primarily through asexual ‘budding’ or clonal growth through simple mitotic cell division. • Capable of aerobic and anaerobic metabolism. Traditional Fermentation: Open System • Open top fermenters protected by a blanket of carbon dioxide during fermentation. • Typical of ale fermentations which are “top fermenting”. • Sanitation is a primary concern; contamination risk is high. • Modern systems utilize closed fermentation. Modern Fermentation – Closed systems Redhook Brewery, Woodinville, Washington Conditioning • Beer requires a period of post-fermentation conditioning. • Flavors “mature” through this conditioning period. • If conditioning is done “cold”, it is referred to as ‘lagering’. • Carbonation usually also associated with the conditioning process. Packaging: Bottling • Often done at high rates. • Beer condition improved if air is excluded. • Must proceed in a sanitary and efficient manner. • Also must avoid high temperatures. Shepherd-Neame Brewery, Faversham, Kent, England Packaging: Kegging • Traditional kegs made from wood. • Modern kegs are stainless steel, typically 15.5 US gallons. • Maintained in cold condition, or beer is flash pasteurized. • Dispensed with carbon dioxide system. Stoudt Brewery, Adamstown, Pennsylvania Beechwood Aging at Anheuser-Busch “Evolution” of Beer Styles1 Witbier pure strain Ales S. delbruckii wheat beers lactic fermentation Berliner Weisse spontaneous fermentation S. cerevisiae “top-fermenting” Weizen roasted barley dark malt Belgian Lambics Stout Porter Brown Ale UK increasing hops & gravity Pale Ale - ESB S. carlsbergensis “bottom-fermenting” + hops pale malt + malt Pilsener Dortmunder Export Germany Vienna Belgium/NL Märzen/Oktoberfest Bock Lagers US Barley Wine Altbier Belgian Ale + malt & sugar Munich India Pale Ale + corn 1Adapted Trappist Ale Cream Ale from M. Jackson, 1988 Beer Summary • Beer is among the oldest beverages made • • • by humans, and has persisted through thousands of years of human development. Both barley and hops require extensive post-harvest processing before the plant material becomes suitable for use in the brewing industry. Beer is a multi-faceted beverage with a rich, intimate history involving plant domestication, selection, and breeding. Beer is one of the “universal” beverages found in most societies around the world. Cheers!