Physiology and Psychology of Flavor Perception

Transcription

1 Physiology and Psychology of Flavor Perception Hildegarde Heymann University of California at Davis, USA January 25, 2014 Flavor is the psychological interpretation of the physiological response to a physical stimulus* Flickr: Libraryman Blog: Reasonably Well Flickr: Like_the_Grand_Canyon *Also affected by vision A range of senses are used when tasting wine. These senses are: sight taste smell touch [hearing] Normal human physiological variation Flickr: Mike McCaffrey 1

2 Appearance First impression Color many expectations The Nature of Color is in the eye.jpg content/uploads/2012/02/color of wine primary indicators.jpg Color is the absence of (certain) wavelengths gcw5gtczjo/txvih fuigi/aaaaaaaah9y/67myzrvpbp4/s1600/seeing+colours.jpg Rods (scotopic vision): abundant in periphery, dim light, B/W Cones (photopic vision): abundant around fovea, bright light, color, 2

3 Different types of opsins: Exact structure of opsin molecule determines maximal sensitivity to lights wavelengths Long wavelength: red light Medium wavelength: green light Short wavelength: blue light COLOR-BLINDNESS Ishihara Plates Molecular Expressions: Optical Primer cvision.shtml 5-8% of males (as high as 1 in 12) 0.5% of females (1 in 200) Normal human color vision variability Rayleigh color test use red & green lights to make yellow Opsin polymorphic variant at amino acid % of red pigments encode for serine 40% of red pigments encode for alanine ser version is red shifted 3-4 nm relative to ala i.e. they need less red light to match the yellow Y = tyrosine, T = threonine, A = alanine, 90% of green pigments encode for ala I = isoleucine, S = serine, F = phenylalanine 10% of green pigments encode for ser Vision Research (2011) volume: 51 issue: 7page:

4 Individual variation of Just Noticeable Differences at isoluminance (8 women; 2 men) 100 Taste versus taste 90 with smell Without smell Percent correct Journal of Vision June 3, 2013 vol. 13 no. 7 article 1 0 Water Vinegar Whiskey Wine Coffee Chocolate Garlic Substance to be identified Taste Five basic tastes sweet, salty, sour, bitter, umami, [fat, water] Oral Sensations: (Chemestesia) astringency, burn/irritation, tingling, temperature Taste final "barrier" function intimate contact least complicated stimulation to perception time is very short Taste: msec Touch msec Vision: msec Hearing: msec Compounds must be dissolved (saliva, wine, etc.) 4

5 Hänig s 1901 dissertation and the tongue map a story about primary resources Sweet, sour salty not much difference Bitter back of palate (mostly due to soft palate taste buds) NY Times, 11/10/08: Leif Parsons Bartoshuk, L.M. (1993). The biological basis of food perception and acceptance. Food Quality and Preference, 4, Purvis et al. (2001) Neuroscience, 2 nd edition Infant Taste Responses sweet sour bitter 5

6 Supertasters Hypertasters Supertasters continued PTC (phenyl thio carbamate) PROP (6-n-propylthiouracil) H-N=C-S group Sensitivity genetic Chromosome #5 (with some effect from #7) May have had evolutionary advantage: Plants high in H-N=C-S group tend to contain toxic elements Protects against goitre (iodine deficiency) Dye tongue blue Count papillae in reinforcement circle at tip <20: nontaster >40: supertaster With thanks to JX Guinard Supertasters continued PROP (propylthiouracil) thresholds 1.E-03 1.E-03 1.E-03 8.E-04 X= 1.14 E-5 std=1.08 E-5 (n=21) PROP thresholds for 41Ss X=1.23 E-4 std= 1.96 E-5 (n=10) X=1.83E-4 std 3.75 E4 (n=10) 6.E-04 4.E-04 2.E-04 0.E supertaster nontaster content/uploads/2007/07/supertasters_nontaster.jpg Supertaster Taster Non-taster 6

7 Supertasters continued Bitterness, sweetness, and liking ratings of unsweetened white grapefruit juice. US population 25% ST, 50% MT; 25%T 35% of woman and 10% men Asians higher proportion ST Hayes J E et al. Chem. Senses 2011;36: The Author Published by Oxford University Press. All rights reserved Bitterness and trigeminal effect of 10% ethanol (Bartoshuk et al. 1994) OLFACTION Intensity Bitterness Burning/ Hotness Nicht Non tasters Schmecker Schmecker Tasters Supertasters Schmecker 7

8 ORTHO and RETRO NASAL OLFACTION Retronasal smell images are IMPORTANT as illustrated by the massive extent to which they interact with these brain systems compared with orthonasal smell images Olfactory Cells Olfactory Mucosa orange-yellow pigment area (2.5 sq. cm) cilia area sq. cm Olfactory cells Very sensitive mercaptans 40 olfactory cells need 9 molecules each 10 million cells Lifespan days axons directly to olfactory bulb no synapses! Aging declines in flavor perception: Retronasal olfaction is more vulnerable to loss than orthonasal olfaction Odor molecules create different patterns of spatial activity in the olfactory bulb. A homologous chemical series (aldehydes) elicits patterns that are overlapping but different, as shown high resolution functional magnetic resonance imaging (fmri) Anosmia Olfactory cell axons pass through cribiform plate Viral infections Gordon M. Shepherd, Nature 444, (16 November 2006) 8

9 Nasal cycle 80% of humans have a nasal cycle lasts 30 min to 5 hours (mean hours) combined flow rate remains constant Odorants attachment to mucosa depends on airflow Some better at low versus high and vice versa Provides two olfactory images of the world Result: better olfactory acuity Scent tracking by humans (Noam Sobel UCB) Porter, et al., (2007) Mechanisms of scent-tracking in humans, Nature Neuroscience 10, apnea prevention.org Aroma: Specific anosmias Specific Anosmia Observed for β-ionone, but not for α-ionone Good sense of smell BUT much less sensitive (at least 100 fold less) 40 of 62 compounds at least 4% of population (Amoore, 1969) androstenone (about 5%) OR7D4 receptor genes Both copies: urine and unpleasant One copy: no or weak odor Mutation in gene: floral and pleasant Compounds at 30+% isobutyraldehyde malty geraniol rose like odor Pentadecalactone musky musk xylol musk odor 1,8 cineole camphoraceous Frequency distribution of β-ionone, and α-ionone orthonasal thresholds in water and deodorized orange juice (pumpout). Concentrations in water or pumpout for steps 1, 6, and 12 are indicated below each compound, accordingly. 9

10 Tempere et al. (2011) The Training Level of Experts Influences their Detection Thresholds for Key Wine Compounds. Chem. Percept. (2011) 4: Aroma Thousands of odors Tip of nose phenomenon Carvone 3 methoxy 2 isobutylpyrazine 3 methoxy 2 isopropylpyrazine musk odors == entirely different families 10

11 Chemical irritation Common chemical sense or chemesthesia Free endings of the trigeminal aka 5 th cranial nerve CO 2 (tingle), capsaicin (burn), mustard (pungency), bite (raw onion), astringency (tannin), pain (chlorine) Dr Spiller.com Often innate dislike (protection) but can be overcome and be pleasurable Astringency of 4 tannic acid samples (1.4 g/l) rated by LR (20), MR(37) and HR(20) subject groups Questions? We live in our own sensory world individual differences in sensory functioning even with simple aromas and flavors will not be similarly perceived as acceptable R=Salivary responsiveness, Low, Medium, High Dinella et al., 2011, Chemical Senses Mela, D. Prepared Foods, July,