The Importance of Aromas and Flavors on Beer Lyn Kruger Siebel Institute of Technology

The sensory analyst is considered an “instrument” Senses are used to: Sensory Analysis The sensory analyst is considered an “instrument” Senses are used to: perceive and react to characteristics of food and beverages

The sensory analyst is considered an “instrument”: Measure Analyze Sensory Analysis The sensory analyst is considered an “instrument”: Measure Analyze Interpret

cognitive and cultural bias individual acuity differences Sensory Analysis Humans as instruments cognitive and cultural bias individual acuity differences

Sensory analysts may vary from one test to the next: Fatigue Sensory Analysis Sensory analysts may vary from one test to the next: Fatigue Adaptation

Ability to discriminate between harmful and benign stimuli Sensory Analysis Ability to discriminate between harmful and benign stimuli Health and age play a role Ability to improve with practice

Sensory Evaluation: What we know Can taste many flavor compounds Basic tastes sweet, salty, sour, bitter, umami Acute sense of smell Trigeminal sensations: burning, cooling, tingling > 1,000 odors and flavors in beer

Olfactory System

Trigeminal Sensation

Sensory Evaluation: Training objectives Establish memory for aromas and flavors recognize and identify aromas and flavors choose correct descriptors

Flavor Wheel

Basic Tastes: Sensory procedure Aroma impressions first, “drive by” then 2-3 short sniffs Small sips Allow sample to sit on tongue for a moment, then swallow

Basic Tastes: Sensory procedure Avoid oversaturation and sensory fatigue Allow 15 - 60 seconds between samples to readapt receptors Less flavored samples before highly flavored samples

Basic Tastes: What happens Beer sample quickly moderates towards 37°C in the mouth Immediate (in some individuals copious) secretion of saliva in response to oral stimulation This is promoted in beer by its acidity, alcohol content and high level of carbonation. Saliva is a well-buffered, high pH (7.0) diluent, and influences the sensory perception of beer

BREWHOUSE ASSOCIATED FLAVORS Lyn Kruger Siebel Institute of Technology

Flavors Associated with Brewhouse Positive Flavors Malty Hoppy Bitter Off flavors Dimethyl sulfide (DMS) Isovaleric acid

Malty: Typical Flavors Standard Malts Cereal Grain Sweet Nutty Malty Caramel/Color Malts Caramel Toffee Slightly burnt Roasted Malts Burnt Bitter Coffee

Use Aroma hop varieties Aroma Associated with Hop Oils : Hoppy & Bitter Hoppy Use Aroma hop varieties Aroma Associated with Hop Oils : Floral Compounds Citrus Compounds “Noble aroma” -herbal, spicy - oxidation products Bitter Use Bittering hop varieties Bitter flavor associated with resins

Dimethyl Sulfide (DMS) Flavor creamed corn, vegetable, oysters, tomato juice Formation Precursor (S-methyl methionine [SMM]) formed in the barley Some SMM remains in the malt During wort boiling SMM is converted to DMS and lost by volatilization

Flavor cheesy, sweat socks Isovaleric Acid Flavor cheesy, sweat socks Production Formed in old hops Organic acid

FERMENTATION RELATED FLAVORS Lyn Kruger Siebel Institute of Technology

Flavors fruity, banana, apples, perfumy, solvent, nail varnish remover Esters Flavors fruity, banana, apples, perfumy, solvent, nail varnish remover Production Reaction of alcohol group and acid group in the yeast cell Iso amyl acetate (Fruity) Ethyl Acetate (Solvent)

Flavor buttery, butterscotch Diacetyl Flavor buttery, butterscotch Production During yeast growth in fermentation When the yeast has to make a specific amino acid - valine

Flavor sulfury, rotten eggs, burnt rubber, striking a match Sulfur Compounds Flavor sulfury, rotten eggs, burnt rubber, striking a match Production Intermediates in amino acid metabolism When yeast needs to make sulfur containing amino acids

STORAGE ASSOCIATED FLAVORS Lyn Kruger Siebel Institute of Technology

Flavors associated with Product Storage Any flavor changes after maturation - generally negative (off-flavors) Few exceptions (e.g. barley wines) Flavors normally associated with staling of the beer Papery Bready/Cooked Skunky Aldehydic

Flavor papery, wet cardboard, stale. Formation Oxidation of linoleic acid Forms trans-2-nonenal (an aldehyde) Very low flavor threshold (1 ppb) Oxygen /light promotes reaction

Flavor cooked breakfast cereal, oxidized, cooked Bready / Cooked Flavor cooked breakfast cereal, oxidized, cooked Formation Overpasteurization( particularly in the presence of air) Oxidation reactions

Flavor Nutty, toffee, honey, green apples, aldehydic Formation Degradation of amino acids Oxidation of higher alcohols Oxidation of isohumulones Oxidation of lipids Oxidation of ethanol (acetaldehyde)

CONTAMINATION RELATED FLAVORS Lyn Kruger Siebel Institute of Technology

Flavors associated with Contamination These flavors are generally off-flavors Can be microbial or non-microbial Microbial Variety - depending on microorganism Cloves (eugenol, 4-vinylguaicol) Acidic (lactic, acetic acid) Diacetyl DMS Sulfur

Microbial: Cloves / Spicy Flavor phenolic, cloves, spicy Formation Associated primarily with wild yeast In some beer styles - deliberate

Flavor sour, vinegar, sour milk, acetic, lactic acid, acidic Formation Beer spoilage bacteria Lactic acid bacteria - Lactobacillus & Pediococcus Produce lactic acid and acetic acid (only Lactobacillus)

Flavor buttery, butterscotch Diacetyl Flavor buttery, butterscotch Formation Beer spoilage bacteria Lactobacillus & Pediococcus Wort spoiling bacteria Enterobacteriacea

Flavor cooked vegetable, corn, olives, oysters DMS Flavor cooked vegetable, corn, olives, oysters Formation Wort spoiling bacteria Often grow in plate heat exchangers

Flavor sulfur, rotten eggs, mercaptan Sulfury Flavor sulfur, rotten eggs, mercaptan Formation Wort spoiling bacteria Beer spoilage bacteria