Flavor = Taste + Aroma. Taste Chemical % sweet sour & acid salty Bitter. Aroma Chemical % grape orange apple bell pepper. Taste.

Transcription

1 Making Sense of Taste The hemistry f Taste & hemesthesis Smith, D.V. Margolskee, R.F. Scientific American March, Percept Salt Sour Sweet Sweet Umami Bitter hemesthesis Taste Psychology hemistry Neurobiology Ligand sodium ion hydrogen ion sugars artificial sweetners glutamate organic bases phenolics Receptor ENa ENa like T1R3 & T1R3 T1R2 & T1R3 T1R1 & T1R3 T2Rs (~30) trigeminal Multivariant Taste of wine Alcohol(?) Bitter (30) Salt (1) Sweet (2) Sour (1) Acid = f(sour, astr.) Astringent(?) Flavor = Taste Aroma Taste hemical % sweet sour & acid salty Bitter sugar Ion &acids Sodium ion phenolics Aroma hemical % grape orange apple bell pepper aminoacetophenone linalool et 2mebutyrate ibu2mepyrazine

2 Taste Small, JonesGotman, Zatorre, Petrides, Evans, 1997, Journal of Neuroscience F Amygdala Smell Zatorre, JonesGotman, Evans, Meyer, 1992, Nature Taste Smell Zald & Pardo, 1997 PNAS Zald, Lee, Fluegel & Pardo.,1998 Brain rbitofrontal cortex Responses to tastants and to odorants converge in rbitofrontal cortex and in forebrain regions such as the amygdala Images provided by Dana M. Small, Northwestern University Feinberg Medical School Sweet T1R3 dimers Percieved Intensity high potency sweetner (aspartame) Threshold oncentration high intensity seetener (sugar) T1R2 T1R3 oncentration of sweetner (dose) 1969 hiral Sweet Ligands 1969 R. S. Shallenberger, T. E. Acree, &. Y. Lee, Nature, 221, Sweet Taste of D and LSugars and Aminoacids and their Steric Nature of the hemoreceptor Site. chloroform A B L A 3Å B L L 3Å A B βd fructose 3Å 1967 A B Theory of Sweet Taste 1967 R. S. Shallenberger & T. E. Acree, Nature, 216, , Molecular Theory of Sweet Taste R. S. Shallenberger & T. E. Acree, J. Agric. Food hem., 17, , Molecular Structure and Sweet Taste. N 3 D Leucine N 3 L Leucine

3 Sensory test Seetness in wine Glucose Fructose Sucrose Score Sugar left at the end of fermentation is glucose. Sucrose 2 Et yeast Fructose Glucose Dissociation Reaction (weak acids) log(k2/ k1) = pka k k2 bitartrate ion hydrogen ion k k4 bitartrate ion tartrate ion hydrogen ion D 2 3D hemical Structure 2 Acidic protons ydrogen ions L 2 2 2T = T, 2.98 T = T2, 4.32 p = pka1 log[t]/ [T] endersonasselbach Equation Ionization Reaction Total Dissociation in strong Base 466 k1 k2 456 bitartrate ion 2.98 hydrogen ion 456 k3 446 K K bitartrate ion Potassium tartrate k4 Potassium bitartrate soluble soluble Insoluble In the lees malic acid lactic acid acetic acid citric acid

4 Measurement of Acid Titration w/ strong base: Sodium ydroxide k Na Na k 2 sodium tartrate malic acid lactic acid acetic acid citric acid Dissociation Reaction (weak acids) A (acid) A (salt) k1 k k 2 /k , , , 4.77, 6.39 Acree 00 k 2 > k 1 p = pk a log[ A]/[A ] p* Total Acidity g/l mmolarity mnormality Plane Sensory Score = f(chemistry) Panel Score malic acid lactic acid % 3.7 citric acid % Total Acid 0.3% p *p adjusted with 5N Na Acid Index = TA (total acid as tartrate) p Astringency is not a taste or olfaction phenomenon, but rather a chemesthetic sense perceived as a tactile sensation by the trigeminal nerve. Astringency has a number of components; these have been described as: drying of the mouth roughing of the oral tissues puckering of the cheeks and muscles Lee and Lawless, 1991

5 Astringency results from foods such as grapes, persimmons, tamarinds, wine, coffee, tea, etc. and is known to be produced by a number of classes of chemicals. ompounds Producing Astringent Sensations Ethanol and some other solvents Salts of multivalent metal cations (particularly Alum = aluminum sulfate) Polyphenols & tannins Inorganic and organic acids Polyphenol Astringency Polyphenol astringency is generally recognized as the result of interactions between prolinerich proteins (PRPs) in saliva and dietary polyphenols. The PRPs and polyphenols combine to form colloidal particles, and this removes the lubricity provided by the PRPs in solution. BateSmith, 1973; Gawel, 1997 Gallic acid Gallotannins 2 ne form of tannic acid Proline is unlike all of the other coded amino acids in having a secondary amine function. protein polyphenols proteinpolyphenol complexes colloidal particles R turbidit y N Proline 2 N ther ommon Amino Acids

6 Mixtures Mixtures Two Taste Interactions Additivity A B = 2A or 2B Suppression A B = 2/3 A & 2/3 B Suppression ne taste mode can suppress the response to another mode, i.e. bitter suppresses sweet. Mixtures: Taste Suppression PT Lawless xxx Taste Suppression is not competitive inhibition Lawless

7 ydrometer : Antoine Baumé 1768 Ébulliomètre ~ 1850 old water %sugar Flame Alcohol Lead Wine Science never ends Near Infrared spectra First 250 years Univariate Science Based on one variable y = mx b Next era Mulitvariate Science Based on many variables Y = mx b Y, X are matrices Multivariant Taste of wine Alcohol(?) Bitter (30) Salt (1) Sweet (2) Sour (1) Acid = f(sour, astr.) Astringent(?)