Brewing Science Flavor and the Origins of Flavor Beer Styles
What is a flavor? A combina=on of taste, odor, and other sensory input Includes mouth feel (tac=le), visual, kinetsthe=c, temperature, pain (nociocep=on), and other senses (carbona=on!) The largest contributors are taste and smell
Taste The taste buds are clusters of approximately 100 taste cells that occur as protuberances, called papillae, on the tongue The arrival of a chemical s=mulant on the surface of a receptor temporarily modifies the cell wall and produces an electrochemical impulse
Smell perceived by neurons in the olfactory epithelium (skin cells) of the upper respiratory passage Some molecules also reach this olfactory ephithelium by way of the back of the mouth during swallowing; this is known as gustatory aroma percep=on
Other Senses Tac=le sensa=ons such as viscosity and the prickle from dissolved carbon dioxide, for example, are determined by the physical composi=on of the beer and also play an important role in zymological evalua=ons. Temperature is extremely important for all aspects of flavor percep=on. Warmer temperatures tend to emphasize the aroma=c components of the beer, while lower temperatures suppress them. It is therefore impera=ve to serve beer at the proper temperature for the style. Psychological factors or the senses of vision and hearing, which may indirectly affect the results of a beer evalua=on. A trained taster should be able to minimize the influence of these external factors while performing a sensory analysis.
How do we measure Flavor? Meilgaard system: concentra=on rela=ve to sensing threshold value Beer Flavor Wheel False measures: IBU and Color Strength / Alcohol Content Others
Meilgaard Thresholds Primary Flavor Cons=tuents (>2 FU) All Beers Ethanol Hop bi[ering compounds Carbon dioxide Specialty Beers Hop aroma compounds Caramel and roasted flavor compounds Esters and alcohols (high gravity beers) Short- chain acids Defec=ve Beers 2- trans- nonenal (oxida=on) Vicinal diketones (diacetyl) Sulfur compounds (H2S, DMS) Ace=c acid (contamina=on) 3- Methyl- 2- butene- 1- thiol (lightstruck) Others (contamina=on) Secondary Flavor Cons=tuents (0.5-2 FU) Vola=les Banana esters (e.g., isoamyl acetate) Apple esters (e.g., ethyl hexanoate) Fusel alcohols (e.g., isoamyl alcohol) C6, C8, C10 alipha=c acids Ethyl acetate Butyric and isovaleric acids Phenylace=c acid Nonvola=les Polyphenols Various acids, sugars, and hop compounds Ter=ary flavor cons=tuents (0.1-0.5 FU) 2- Penethyl acetate, o- amino acetophenone Isovaleraldehyde, methional, acetoin 4- Ethylguaiacol, g- valerolactone Background flavor cons=tuents (< 0.1 FU) Remaining flavor compounds
Interna=onal Bi[ering Units Dis=nct from Flavor profile Based on UV/Vis measurement of extracted iso- alpha acids
Color Degrees Lovibond is derived from comparison of color to standardized scale, largely replaced by other methods (Standard Reference Method) that give approximately equal results SRM measures light at 430 nm: SRM = 12.7 x dilu=on factor x Abs 430
Malt Analysis Color Tradi=onal Method developed by Lovibond. The scale is implemented by comparing colored slides or glasses to a sample to visually see which slide agreed with the color of the sample Current standards for measuring color Standard Reference Method (SRM) developed by American Society of Brewing Chemists (ASBC) European Brewing Conven=on (EBC) color ra=ng The two methods can be compared by the equa=on EBC = 1.97 * SRM Provided by Ken Woodson & the North Texas Home Brewers Associa=on
Malt Analysis Color The current methods use spectrophotometers All three scales goes from low to high, with lower numbers assigned to light colors For light colored beers the SRM method is very close to the Lovibond scale Provided by Ken Woodson & the North Texas Home Brewers Associa=on
Malt Analysis Alpha- amylase (Dextrinizing Units) ASBC metric that measures dextrin units per 100 grams Over modified malt normally has lower dextrin units. For less modified malts, the dextrinizing units needs to be greater to apply an infusion mash. Typical ranges for 100 grams: Six row malt 35-45 American two row malt 40-50 Pilsener malt 44-48 Vienna malt 40-45 Provided by Ken Woodson & the North Texas Home Brewers Associa=on
Malt Analysis Diasta9c Power (Degrees Linter) Measures the enzyme content of the malt. Specifically, the enzyme strength to convert starch to sugar Higher diasta=c power malts convert starches faster than lower diasta=c power malts Well modified malts with low protein content typically have a diasta=c power between 35 and 40. On the other hand, it can be as high as 160 for six row brewers malt. Diasta=c power decreases as malt color increases. Provided by Ken Woodson & the North Texas Home Brewers Associa=on
Malt Analysis Protein Percent Equals 6.25 =mes the total nitrogen content The protein percent for Barley malt should be 9 to 11% Enzymes are proteins, so higher protein levels correspond to higher enzyma=c strength. Provided by Ken Woodson & the North Texas Home Brewers Associa=on
Malt Analysis Soluble Nitrogen/Total Nitrogen Ra9o The ra=o of soluble nitrogen to total nitrogen is a measure of malt modifica=on. A higher ra=o indicates higher malt modifica=on For lager malts, 30-33% indicates under modifica=on and 37-40% indicates over modifica=on. For infusion mashing, the ra=o should be 38-42% Provided by Ken Woodson & the North Texas Home Brewers Associa=on
Malt Analysis Mealy Percent Malt is characterized as mealy, half- glassy, and glassy. Mealy malt is very chewable, whereas, glassy malt is very hard. Well modified malt is mealy. For infusion mashing, the malt should be at least 95% mealy. Malt should be at least 92% mealy for decoc=on and step mashes. Provided by Ken Woodson & the North Texas Home Brewers Associa=on
Malt Analysis Example Let s review a typical malt analysis from Briess Malt and Ingredients Co. h[p://www.briess.com/brew/products.shtml Provided by Ken Woodson & the North Texas Home Brewers Associa=on
Beer Strength Most accurate (but =me- consuming) method would be dis=lla=on and measurement of alcohol content Instead, Density is usualy used as an approxima=on Specific Gravity: density rela=ve to pure water Water is 1.000, pure alcohol is 0.789
Beer Strength Original Gravity (OG) is specific gravity BEFORE fermenta=on (also called original extract) Final Gravity (FG) is specific gravity AFTER fermenta=on ABV% (105 x (OG- FG)) / (0.79 x FG)
Beer Strength Many systems for measurement of density: points, brix, degrees Plato, etc Points is simply the thousands of a specific gravity: SG 1.020 = 20 points Bri=sh Brewers oren use degrees Plato, which is roughly: points / 4 (so SG 1.020 5 degrees Plato)
Beer Styles The idea of dis=nct, recognizable styles is mostly a modern inven=on (1977+), but has become big business Style can include measurables such as color, flavor, strength, but also includes intangibles such as produc=on method, history, or country of origin
Beer Styles Divided tradi=onally between Ale and Lager styles
Types of Beer Ales Use top- fermen=ng yeast which is unable to metabolize certain sugars. This results in a frui=er, sweeter beer. Top fermen=ng yeast rises to the top of the vessel during fermenta=on. Fermented at higher temperatures than lager beer (15 23 C ) Ale yeasts at these temperatures produce significant amounts of esters resul=ng in a flowery, fruity aroma Pale ale Brewed using a pale barley malt. Hop levels can vary. Dark ale Brewed using dark roasted barley malts. Also called stout. Irish red ale The red colour comes from the use of roasted barley. Has a malty, caramel flavour. Cream ale Brewed to be light in colour, hop and malt flavour is subdued. Brown ale Brewed with a darker barley malt, lightly hopped and fairly mildly flavoured with a slightly nu[y taste.
Top Fermen=ng Wheat Beers Pure Yeast Lac=c Fermenta=on Spontaneous Fermenta=on South German Weissbier/ Weizen Weizenbock Berliner Weisse Lambic Gueuze Faro Kriek Frambooise Other Fruit Beers Sweet Stout Porter Oatmeal Stout Dry Stout Imperial Stout Ale Types American Ale Cream Ale Bi[er Best Bi[er Strong Bi[er So English Brown Ale No English Brown Ale Old Ale Pale/Dark Barley Wine Light Ale Pale Ale Irish Red Ale Strong Scotch Ale Pale Mild Dark Mild Belgian Brown/ Red India Pale Ale Belgian Ales Altbier Saisons Trappisten Belgian Witbier/ White/ Blanche Dunkel- Weizen American Hefeweizen Ale Styles
Types of Beer Lager The most commonly consumed style Fermenta=on occurs at around 7-12 C using a bo[om fermen=ng yeast Fermenta=on phase Then cooled at 0-4 C Lagering phase The lager clears and mellows Inhibits the produc=on of esters, resul=ng in a crisper (less fruity) tas=ng beer Has more fizz than ale Premium Lager? No such thing.
Lager Styles Bo[om Fermen=ng Lager Vienna Type Munich Type Pilsener Dortmunder/ Export Strong Lager Marzen/ Dark Pale Dark Oktoberfest Bock American Malt Liquor Pale Bock Rauchbier Pale/Dark Double Bock