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out of the sensory box final


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out of the sensory box final

  1. 1. Out of the sensory box: exploring the physics of mouthfeel George van Aken Jennifer Aniston (W Magazine photo shoot) - 40% NIZO food research - 60% independent scientist: insight Food inside
  2. 2. 2Together to the next level GUIDED TOUR IN THE PHYSICS OF MOUTHFEEL
  3. 3. Back to the basics 3 Food structure and composition Interaction with the body: • Receptors • Oral processing • Digestion Consumer experience • Sensory perception • Appetite and Satiety • Liking Which adaptations needed?
  4. 4. After taste oral and pharyngeal coating, flavour release Masticatory oral processing structural changes, flavour release bolus formation Subsequent perceptive stages First bite rheology, temperature Appearance color, shine, structure, flow, smell swallow Neural and hormonal Feed back Digestion, absorption, glucose homeostasis, … Hedonic response, Wanting, Remembrance satiety, satisfaction, craving sensory perception cephalic response
  5. 5. For example, ice cream goes from thick to creamy to liquid before swallowed 0 = start 1 = finish/swallow Sequential perception as measured by Temporal Dominance of Sensations (TDS) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 t (s) %attributeselections normalised TDS: 2 LF Firmness Melted Sandiness Slippery Spreadability %attributeselections t (normalized) Thick Creamy Liquid Together to the next level Task: Choose which attribute is currently dominant: creamy thick sweet smooth liquid Acknowledgement Harold Bult
  6. 6. In silico digestive physiology modelling • Timing of meals and drinks • Speed of consumption • Proteins, sugar, fat, water, pH • Other compounds together or separate from meal Input parameters: diet timing and properties Output: temporal variations • Gastric pressure • Gastric pH • Gastric emptying • CCK, PYY, GLP-1, GIP • Digestive enzyme activity • Bile secretion • Small intestinal pH • Absorption • GI transit • Insulin Hunger, fullness, bloating, satiety, reward Timed release Bioavailability Blood glucose Physiology literature In vitro measurements Physiological variations (infants, elderly, diseased)
  7. 7. MOUTHFEEL What do we sense? 7Together to the next level
  8. 8. What produces the forces sensed by the tongue? Viscous forces of the fluid Friction of tongue and palate in contact Particles grinding between tongue and palate palate tongue 8Together to the next level
  9. 9. Similar textural sensory attributes for skin and mouth • Thick, viscous • Stiff, gelled • Elastic • Firm, hard • Crumbly • Stringy 9Together to the next level • Rough • Smooth • Slippery • Non-slipping • Velvety • Fatty • Tough • Short, long • Shear thinning • Thixotropic • Melting • Gritty(grainy) • Sticky • Soft • Hard • Sandpaper Rheometers Tribometers
  11. 11. M. Trulsson, G.K. Essick, J. Neurophys. 1997(77), 737-748 Tongue mechanoreceptors Rapidly Adapting receptors: sensitive to force variations • Lower stress threshold of about 12 Pa • Average stress threshold of about 60 Pa • Rheology: vibrations caused by fracturing • Tribology: vibrations caused by tumbling particles, surface roughness 11Together to the next level Slowly Adapting receptors: sensitive to constant forces • Rheology: bulk viscous forces • Tribology: static surface friction forces
  12. 12. BOUNDARY AND HYDRODYNAMIC FRICTION 12Together to the next level
  13. 13. Transition to hydrodynamic lubrication 13Together to the next level
  14. 14. Optical Tribological Configuration 14 Object on moving plate
  15. 15. Papilla roughness and deformability Variation of normal stress (piglet tongue, OTC) Frame size: 75 mm * 125 mm Filiform papilla Glass slide Papilla surface roughness ~ 20 μm -- 0 kPa 4.7 kPa 6.7 kPa 9.5 kPa 15 kPa 20.6 kPa
  16. 16. Generation of asymmetry in deformable symmetrical bodies by hydrodynamic forces No net lift force undeformable “steel window wiper” velocity Net lift force deformable “rubber window wiper” velocity Van Aken, G.A., Modelling texture perception by soft epithelial surfaces, Soft Matter, 2010, 6, 826–834 Shear force Shear force Lift force
  17. 17. Tribological regimes (Stribeck curve) Static friction speed  viscosity normal force Friction force hydrodynamic boundary mixed Only viscous forces Static surface bonds Transient surface bonds and corrugations Liquid starts to interpenetrate palate papilla Together to the next level Smaller particles can slip through Gap-width increases with viscosity 
  18. 18. Together to the next level Fluidic food bolus gapwidth
  19. 19. Example: for emulsions Thickness and Creaminess are not the same: creaminess correlates to thickness only in the presence of emulsified fat The difference is related to the presence of a fatty coating on the oral surfaces: barrier & lubricant Higher viscosity from: • More emulsified fat • More thickener, starch, protein • More droplet aggregation Higher viscosity from: • More thickener, starch, protein
  20. 20. The oral environment: restructuring effects • Temperature • Melting of solid fats (chocolate) • Melting of gelatin • Shear • Breakup of gels, mixing with saliva • Produces a swallowable paste of smaller gel particles • Rubbing between tongue and palate • Reduces the viscosity: thixotropy of gels, shear thinning behaviour of thickened fluids • Saliva • Dilutes > reduces viscosity-increase obtained from emulson droplets, particles and polymer thickened fluids • Contains α-amylase which breaks down starch polysaccharides > thinning of starch-based thickened fluids and gels • Contains highly glycosylated HMW proteins (mucins) > aggregation of microbes, particles > cleaning activity, viscosity increase > bolus formation, viscous, semi solid, slippery to assist swallowing > lubrication > mucins flocculate on acidification > loss of lubricating function • Mucus coating on the eptithelial surfaces (tongue, gums, palate) • Protective gel layer, provides lubrication • Teeth • Fracturing, deminution, reshaping gels into a bolus of a fluidic dispersion 20Together to the next level MUC5B; 10-40 MDa MUC7; 200 kDa
  21. 21. Interaction with the tongue a thin coating of (emulsified) fat reduces boundary friction Visualization of fat retention on piglet tongue Emulsion: 10 wt% SF oil; 1 wt% WPI CSLM image (Nile blue staining) 500500 mm red: oil; green: tongue papillae Dresselhuis et al., Journal of Colloid and Interface Science (2008) 21 Human tongue
  22. 22. Emulsion droplets increase creamy mouthfeel because: • As filler particles they increase the viscosity • of saliva • of viscous food media • filler effect enhanced by aggregation/clumping • As oil releaser help to reduce boundary friction • Driven by coalescence with tong surface • larger droplets • more solid (saturated) fat by partial coalescence • less stable droplet interface (emulsifiers, lipids, proteins, hydrophobised starch) • For cheese • Fat helps to break up and hydrate the casein matrix into a viscous paste 22Together to the next level Tongue scraping Saliva Guar Couva 760P OSA
  23. 23. 23 Together to the next level Low-fat hard cheese Slowly hydrating dense cheese particles Thin dilute emulsion of small droplets 23 Normal hard cheese Forgeable particles, quickly hydrating Viscous concentrated emulsion of aggregated droplets Solids: breakdown path of fracturing and dissolution important separation
  24. 24. ACOUSTIC TRIBOLOGY Direct in-mouth measurement of boundary friction Together to the next level
  25. 25. New measuring technique: Acoustic tribology van Aken, Food Hydrocolloids, 31 (2013), 325-331 25 In vivo measurement of sound emission due to tongue friction/roughness. New variant allows external measurement "Sandpaper Ballet" Leroy Anderson (1954)
  26. 26. Acoustic tribology: the principle 26 Microphone line voltage during rubbing of the tongue; sequence of products spectrum analysis, selected frequency range saliva creamer honeymargarine vinegar peanut butter spectrum analysis Acoustic signal or tongue roughtness • Decreases with the viscosity of the tongue coating • Increases with acidity/astringency
  27. 27. Examples Black coffee – white coffee Water - banana Water - white coffee
  28. 28. Acoustic tribology: variation in fat content in dairy products In vivo acoustic measurement of tongue roughness, which is directly related to creaminess and astrigency, showing that the effect of fat content differs with dairy product type. 28 lesscreamy 0 0,0001 0,0002 0,0003 0,0004 0,0005 0,0006 0,0007 0,0008 0,01 0,1 1 10 100 integratedacousticsignal(a.u.) fat content (weight %) Milk Yoghurt Cheese T/P Cheese T/C Quark
  29. 29. Effect of half-fat creamer on coffee 0 0,0001 0,0002 0,0003 0,0004 0,0005 0,0006 0,0007 1 saliva coffee black coffee with creamer creamer creamer later Astringency of coffee: acidity and phenolic compound bind the lubricating salivary mucins, Astringency of coffee Smoothening by creamer
  30. 30. Kinetics system: cream after saliva Observed are the effects of inhomogeneous mixing and finally a replacement of native mucosal layer by a lubricating fat layer0,0E+00 2,0E-05 4,0E-05 6,0E-05 8,0E-05 1,0E-04 1,2E-04 1,4E-04 integratedacousticsgnal(a.u.) saliva cream 2 s cream 2,3 s cream 2,7 s cream 2,9 s cream 3,1 s time
  31. 31. Electret tongue rubbing Sensitive to tooth plaque and pellicle 31 recorder • Low-frequency sound enhanced when saliva is replaced by both types of fruits (banana, orange) • High-frequency sound strongly increased for banana compared to saliva and orange Tongue tip rubbed horizontally (left to right) against back of upper incisors. saliva orange banana
  32. 32. recorder Electret tooth tapping sounds 32 Tapping of teeth: • Banana produces a pellicle that dampens high frequencies • Orange removes this banana pellicle Tapping of teeth before and after removal of plaque by tooth brushing: • Bacterial plaque dampens the high frequency sounds >100x at 10 kHz orange banana CLEAN PLAQUE Molars Incisors Molars Incisors Incisors
  33. 33. CRISPY AND CRUNCHY 33Together to the next level Texture technologies Texture technologies
  34. 34. Chocolate rice cracker 34Together to the next level Smaller bits quickly get softened by saliva  fractering sound disappears Single bite: about 10 chews
  35. 35. Comparison between crispy and/or crunchy food products • Fresh from the pack 35Together to the next level
  36. 36. First bites Loudest of first 3 bites 36Together to the next level • Crispness relates to high amplitudes in frequencies 2-10 kHz; highest for Pringles, lowest for Brioche • Snap relates to a peak around 1 khz and a relative strong decay to higher frequencies; highest for carrot and freshly roasted Pecan nut; Buggles and Wokkels also shows snapping features
  37. 37. Duration of sound from the first bite loudest of first 3 bites 37Together to the next level Fracture propagates laterally through a thin sheet Teeth squash through a thick layer of material
  38. 38. Cruchiness • Extented sequence of sound generating chews ( > 3 kHz) 38Together to the next level Pringles Dorito’s Nibbits Lay’s natural “typewriter song” Leroy Anderson (1950) Henri Matisse (1910)
  39. 39. Stailing • Loss of crispy chrunchy behaviour in the open air: first bites 0, 1 and 5 h 39Together to the next level
  40. 40. Mixed chewing and rubbing Chewing a cashew nut and intermittent tongue rubbing 40Together to the next level chewing rubbing 0 rubbing 1 rubbing 2 rubbing 3 rubbing 4 chewing chewing chewing native large particles formed • Large particles disappear from oral coating • Lubrication increases (fat, viscous bolus?) Particles Lubrication by fat
  41. 41. Panel versus Acoustic - Quantitatively measurable in 1 subject - Fast, high time resolution - Directly related to oral food behaviour - Not affected by other sensory cues - Differences between subjects measurable - Limited to tactile cues - Labour intensive panel - Consensus on sensory descriptors needed - Repeatabiliy among panels often limited - Aroma/tastant/tactile cues affect each others - Statistics - No direct relation with the physics involved - Sensory stimuli vary before, during and after oral presence
  42. 42. Understanding and control of oral processing has greatly supported product development Together to the next level
  43. 43. 43Together to the next level Together to the next level Creating the future together