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The Importance of Aromas and Flavors on Beer. Lyn Kruger Siebel Institute of Technology. Sensory Analysis. The sensory analyst is considered an “instrument” Senses are used to: perceive and react to characteristics of food and beverages. Sensory Analysis.
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The Importance of Aromas and Flavors on Beer Lyn Kruger Siebel Institute of Technology
Sensory Analysis The sensory analyst is considered an “instrument” • Senses are used to: • perceive and react • to characteristics of • food and beverages
Sensory Analysis The sensory analyst is considered an “instrument”: • Measure • Analyze • Interpret
Sensory Analysis • Humans as instruments • cognitive and cultural bias • individual acuity differences
Sensory Analysis Sensory analysts may vary from one test to the next: • Fatigue • Adaptation
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
Sensory Evaluation: Training objectives • Establish memory for aromas and flavors • recognize and identify aromas and flavors • choose correct descriptors
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 • Roasted Malts • Burnt • Bitter • Coffee • Standard Malts • Cereal • Grain • Sweet • Nutty • Malty • Caramel/Color Malts • Caramel • Toffee • Nutty • Slightly burnt
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
Isovaleric Acid • Flavorcheesy, sweat socks • Production • Formed in old hops • Organic acid
FERMENTATION RELATED FLAVORS Lyn Kruger Siebel Institute of Technology
Esters • Flavorsfruity, 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)
Diacetyl • Flavorbuttery, butterscotch • Production • During yeast growth in fermentation • When the yeast has to make a specific amino acid - valine
Sulfur Compounds • Flavorsulfury, 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
Papery • Flavorpapery, wet cardboard, stale. • Formation • Oxidation of linoleic acid • Forms trans-2-nonenal (an aldehyde) • Very low flavor threshold (1 ppb) • Oxygen /light promotes reaction
Bready / Cooked • Flavorcooked breakfast cereal, oxidized, cooked • Formation • Overpasteurization( particularly in the presence of air) • Oxidation reactions
Aldehydic • FlavorNutty, 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 • Flavorphenolic, cloves, spicy • Formation • Associated primarily with wild yeast • In some beer styles - deliberate
Acidic • Flavorsour, vinegar, sour milk, acetic, lactic acid, acidic • Formation • Beer spoilage bacteria • Lactic acid bacteria - Lactobacillus & Pediococcus • Produce lactic acid and acetic acid (only Lactobacillus)
Diacetyl • Flavorbuttery, butterscotch • Formation • Beer spoilage bacteria • Lactobacillus & Pediococcus • Wort spoiling bacteria • Enterobacteriacea
DMS • Flavorcooked vegetable, corn, olives, oysters • Formation • Wort spoiling bacteria • Often grow in plate heat exchangers
Sulfury • Flavorsulfur, rotten eggs, mercaptan • Formation • Wort spoiling bacteria • Beer spoilage bacteria