Flavor Production and Control

Off-flavor training © 2017 by Ron Downer Master Brewer

Tasting procedure

Beer Flavor Wheel

Acetaldehyde Green Apple Flavor The Aldehyde found in highest concentration Produced by yeast and is the immediate precursor of ethanol Likely a sign of poorly performing yeast Can also be caused by bacterial spoilage (Zymomonas) Some other flavors from this may be apple skin or grassy. Threshold is around 10 ppm. This is most commonly a symptom of too-young, or “green” beer and should never be detectable. Threshold in beer: 10-20 mg/L Concentration: 45 mg/L Beer Flavor Wheel #0150 Acetaldehyde

Acetic Acid Sour, vinegar flavor Formed by Acetobacter, which transforms alcohol into acetic acid Requires oxygen to form Common in oak-aged beers Threshold in beer: 60-120 mg/L Concentration: 360 mg/L Beer Flavor Wheel #0910 Acetic Acid

Almond Marzipan, Nutty, Nut-Like, or bitter almond Caused by Benzaldehyde, an aldehyde which is also a primary contributor to a sherry-like flavor Can be a result of oxidation. Threshold in beer: 1.0 mg/L Concentration: 3.0 mg/L Beer Flavor Wheel #0224 Almond

bitter Bitter, Hoppy Isomerized hop alpha acids Should be clean and pleasant, without harsh, woody, or astringent character Threshold in beer: 7-15 mg/L Concentration: 24 mg/L Beer Flavor Wheel #1200 bitter

Butyric Acid Putrid, baby vomit, rancid butter Caused by bacterial contamination Often a marker for Lactobacillus Develops in spent grain If you have ever smelled spent grain that has been sitting out overnight in warm weather you know what we are talking about. Threshold in beer: 3.0 mg/L Concentration: 7.5 mg/L Beer Flavor Wheel #0614 Butyric Acid

Caprylic acid Goaty, animal, sweat socks, fatty, candle wax Can be result of microbial contamination or yeast breakdown at maturation Specific to certain beer styles, particularly long- aged lagers Threshold in beer: 5-10 mg/L Concentration: 31.5 mg/L Beer Flavor Wheel #0611 Caprylic acid

Contamination Sour and buttery Lactobacillus contamination Sample is composed of Diacetyl and Acetic Acid Contamination

DMS (Dimethyl sulfide) Cooked corn or vegetables (parsnip, cabbage); more like tomato juice in dark beers Acceptable in small amounts in lagers Created in boil from SMM(s-methyl methionine) Can also be caused by delay in cooling wort, or by bacterial spoilage (Obesum, bacterium proteus). Threshold in beer: 25-50 𝝁𝒈/𝑳 Concentration: 200 𝝁𝒈/𝑳 Use a long, rolling, open boil. Cool quickly (within 90 minutes after end of boil) before pitching yeast. Do regular checks for possible sites for infection. Use a healthy, vigorous yeast starter. Beer Flavor Wheel #0732 DMS (Dimethyl sulfide)

Buttery, butterscotch, movie popcorn aroma or flavor Buttery, butterscotch, movie popcorn aroma or flavor. Can manifest itself as a slick mouthfeel. One of two significant vicinal diketones (VDKs) found in beer. Caused by not performing a diacetyl rest in lagers, or by separating beer from yeast too early. Can also be caused by contamination from dirty draft beer lines. Threshold in beer: 0.1-0.2 mg/L Concentration: 0.6 mg/L Beer Flavor Wheel #0620 Diacetyl

Earthy Usually perceived as wet, damp, or freshly dug earth. Not a common taint in beer. Due to either contamination of water or to storage of packaged beer in a damp area such as a cellar. Some hop varieties can impart an earthy character to beer. Threshold in beer: 5.0 𝝁𝒈/𝑳 Concentration: 15 𝝁𝒈/𝑳 #0841 on the Beer Flavor Wheel Earthy

Nail polish remover or solvent Nail polish remover or solvent. Sometimes evident as an eye-watering sensation. An important contributor to fruity aromas in beer in small amounts. In larger amounts may be sign of too-high fermentation temperatures , improper wort aeration, or other yeast stress. Often found in very high-alcohol beers. Threshold in beer: 20-40 mg/L Concentration: 60 mg/L Beer Flavor Wheel #0133 Ethyl acetate

Ethyl hexanoate Ripe apple, hints of aniseed, licorice. Present in all beers in varying concentrations. Becomes an off-flavor at high concentrations. Produced by yeast during fermentation. Threshold in beer: 0.2 mg/L Concentration: 0.6 mg/L Also known as ethyl caproate. Beer Flavor Wheel #0132 Ethyl hexanoate

geraniol Rose like, floral, or rose water flavor. Imparted to beer by hops (an important character of hop oil). Threshold in beer: 100-200 𝝁𝒈/𝑳 Concentration: 450 𝝁𝒈/𝑳 Beer flavor wheel #0162 geraniol

grainy Husk-like, nut-like, astringent. Sometimes described as “husky” Can be caused by excessive run-off from lauter tun (trying to get that last bit of sugar from the grain bed), insufficient wort boil, high mash pH, high pH of the sparge liquor, and excessive agitation of the mash. Beer Flavor Wheel #0310 grainy

Hefeweizen Spicy and banana Composed of Isoamyl Acetate (banana) and 4-Vinyl Guaiacol (clove) Created by yeast during fermentation Usually found in specific beer styles Sample is combination of eugenol (clove) and isoamyl acetate (banana) Hefeweizen

Farm, barnyard Commonly caused by bacterial infection during fermentation Indole

Isoamyl acetate Banana, bubble gum, peardrop A fermentation product formed during fatty acid synthesis and then leaks out of yeast cells. Important contributor to fruity aromas in beer in small amounts Can be caused by too-high fermentation temperatures, low aeration, or other yeast stress Beer Flavor Wheel #0131 Isoamyl acetate

Isovaleric acid Cheesy, old hops, or unclean sweat socks aroma Common source is use of old, degraded hops Organic acid formed during improper storage of hops Rare in commercial beer Beer Flavor Wheel # 0613 Isovaleric acid

Lactic acid Sour, sour milk Commonly caused by beer spoilage bacteria (e.g. from Pediococcus, Lactobacillus spp.) Beer Flavor Wheel # 0920 (sour) Lactic acid

Light-struck Skunky, sulfury, or rubbery aroma Formed by reaction of a precursor in hop compounds (isohumulones) to blue light Caused by improper packaging (clear or green bottles) Beer Flavor Wheel # 0724 Light-struck

Mercaptan Sewer-like, drains Commonly from poor yeast health, autolysis Beer Flavor Wheel # 0722 Mercaptan

Metallic Metal, tin-like, blood, rusty Present due to water sources, rusty pipes, non- passivated vessels Can also be caused by excessive recirculation of a DE or sheet filter (more than 20 minutes) which extracts beer soluble iron from the DE Beer Flavor Wheel #1330 Metallic

papery Wet cardboard, stale, oxidized Product of oxidation, staling, high headspace airs Also caused by air contact in maturation, filtration, or bright beer tankage Beer Flavor Wheel #0820 papery

Spicy (Eugenol) Cloves, allspice, cinnamon, nutmeg Eugenol is a strain dependent if dominant and is a trait of wheat beer yeasts It is a wild yeast defect in other beers Beer Flavor Wheel #0111 Spicy (Eugenol)

Vanilla (vanillin) Custard powder, vanilla essence A common wood flavor in barrel-aged beers such as Flanders red ales One of a number of phenolic compounds that can occur in beer Beer Flavor Wheel #1003 Vanilla (vanillin)