Tribological principles of oral texture sensation and perception

1. Tribological principles of oral texture
sensation and perception
Jianshe Chen and Rituja Upadhyay
School of Food Science & Biotechnology,
ZJSU, Hangzhou, China

2. FOODTEXTURE DEFINITIONS
▪ Texture is the composite of attributes which arise from the structural elements of foods and the manner in which it
registers with the physiological senses.
(Philip Sherman, 1970)
▪ Food texture is defined as the properties of a food that are that group of physical characteristics arising from the
structural elements of the food, primarily sensed by the feeling of touch, related to the deformation,
disintegration, and flow of the food under a force, and measured objectively by functions of mass, time, and
distance.
(Malcolm Bourne, 1982)
• Texture is the human physiological-psychological perception of a number of rheological and other properties of
foods and their interactions.
(McCarthy, 1987)
• Texture is a sensory property
(Szczesnaik, 1963, 2002)

3. Instrumental measurement Sensory analysis
• Bulk mechanics
• Rheology
• Tribology
• Hedonic (acceptability)
• (Time-) intensity
Correlations
Objective Subjective
Challenging
Physical mechanisms
3
TEXTURE PERCEPTION: Holistic view

4. Initial
(perceived
on first bite)
• Mechanical properties
(hardness, viscosity,
brittleness)
• Geometrical properties
(e.g., shape & size)
Masticatory
(perceived
during
chewing)
• Mechanical properties
(adhesiveness,
chewiness,
gumminess)
• Geometrical properties
(e.g., shape & size)
Residual
(changes
made during
mastication)
• Rate of breakdown
• Type of breakdown
• Moisture absorption
• Mouth coating
CONSUMER PERCEPTION: not solely one “phase”
Texture Profile Method, M.A. Brandt et al. (1963) Journal of Food ScienceV28 N4 404-409
Foodtextureperceived
duringoralprocess
Degree of structure, the
mechanical/rheological
behaviour
Degree of lubrication, the
oral experience or saliva
participation
Time, sequences of oral
processing

5. FOOD RHEOLOGY
• The study of the
deformation and
flow of raw
materials,
intermediate, and
final products of
the food industry
PSYCHOPHYSICS
• Relationship
between
measurable stimuli
and corresponding
human response
PSYCHORHEOLOGY
• Deals with the
sensory perception
of rheological
properties of foods
‘ORAL’TRIBOLOGY
• Lubrication
behaviour of
liquid/semi-solid
foods affecting
mouthfeel**
(astringency,
smoothness)
BULK MECHANICS
• Deals with the
fracture and failure
of materials (large
strain rheology)
HOWTO MEASURE/SENSETEXTURE
**Mouthfeel is more than just flow properties. It includes fracture and failure (large
strain rheology), but it is also driven by friction and lubrication properties

6. Qi He, Joanne Hort, BettinaWolf. (2016). Food Hydrocolloids, 61, pp. 221-232.
https://doi.org/10.1016/j.foodhyd.2016.05.010.
RHEOLOGY PERSPECTIVE OF ORAL PROCESSING
(Case study)
• ‘ Thickness’ correlated to low shear and
high shear viscosity.
• ‘Stickiness’ and ‘Mouthcoating’ prediction
improved with extensional viscosity.
• Sweetness and flavour perception
positively correlated.
• Sweetness and degree of shear thinning
inversely correlated.

7. Kurotobi et al. (2018). J.Texture Stud.
Volume 49, Issue 4 (Cover Image)
https://doi.org/10.1111/jtxs.12355
RHEOLOGY PERSPECTIVE OF ORAL PROCESSING

8. Tribology zone Rheology zone
<0.1 m 1 m 10 m 100 m
Lubrication
solution
limited,
saliva limited,
“surface
dominated”
Composite
behaviour,
related
To phase ratio,
“particle
dominated”
Yield
stress
related
Viscosity,
diffusion,
“solution
dominated
”
Controlling
elements
Thickness, Firmness,
Melting, & Breakdown
Creaminess, Fattiness, Smoothness, & Slipperiness
Astringency,
Roughness & Afterfeel
Sensory
attributes
Gap
width
TRIBOLOGY PERSPECTIVE OF ORAL PROCESSING

9. PARAMETERS INFLUENCING FOOD ORAL LUBRICATION
Food Oral
Lubricity
(Tribology
system)
Food system
# Chemical properties
#Physical properties
# Stability
Oral conditions
# Oral temperature
# Residence time
#Tongue-palate
pressure
Saliva
# Flow rate
# Composition
# Stimulated/
unstimulated
Surface
#Tongue surface
roughness
#Tongue speed
# Direction of
movement of tongue
‘ORAL’TRIBOLOGY/ORAL PROCESSING/BIOTRIBOLOGY

10. Kokini’s physical model of oral lubrication: Two plates
squeezed by normal force W, v is the velocity with which
the tongue moves; h is the distance between the tongue
and the roof of the mouth. Kokini et al. 1977.
Friction tester apparatus Mini-traction machine (MTM)
Optical tribological
configuration (OTC)
Double-ball tribological system
TRIBOLOGY CONFIGURATIONS
Three ball-on-disc/TA Ball-on-three plate

11. Mosca & Chen.Trends in Food Science &Technology (2017), 66, 125-134.
SALIVA & FOOD-SALIVA INTERACTIONS
Coating &
Clustering
Colloidal
Interactions
Complexatio
n
Enzymatic
breakdown
Binding of
Aroma
compounds
• (Partial) hydrolysis of
macromolecules
• Changes in rheological properties
• Conversion of aroma compounds
• Impact on texture and
flavour perception
• Changes in aroma release
• Impact on flavour perception
• Facilitate deformation and
breakdown of food structure,
bolus formation & swallowing
• Dissolution and transport of tastants
• Changes in rheological properties
of colloidal systems
• Impact on texture and
fat-related attributes
• Decrease of lubrication and
increase of friction
• Rise of astringency and
friction-related sensations

12. SENSORY
ORALPROCESSING
TRIBOLOGY
ASTRINGENCY PERCEPTION
Brossard et al. (2016). J.Texture Stud., 47: 392-402.

13. ASTRINGENCY PERCEPTION
MECHANISMS IN LITERATURE
Upadhyay et al. (2016). J. Phy. D: Appl. Phy., Special Issue:The Phy.Food, 49 (10), 104003

14. SMOOTHNESS PERCEPTION
• Smoothness perception is related to friction
between the tongue and the palate
• The o/w emulsions can be differentiated for
smoothness perception based on oil mass
fraction and type of emulsifier
• Oral tactile measurements correlated strongly
with friction coefficients than finger tactile
measurements
• Tongue surface is highly sensitive to the vibro-
tactile sensation compared to the innervation
of the finger tips.

15. SMOOTHNESS PERCEPTION
• COF & smoothness scores show
significant correlations between 0.1 and
30 mm/sec constituting mixed and
hydrodynamic regimes.
• Correlations were made between oil
content, friction coefficient, viscosity and
smoothness scores
• The apparent viscosity at a shear rate of 50 s−1 was
found to have a very significant effect on perception
of smoothness using oral tactile measurements.
Upadhyay & Chen (2019). Food Hydrocoll. 87, 38-47

16. Mechanoreceptors: tissue filters between stimulus and nerve ending
detect local friction and pressures changes at the food-mucosa interface
• The oral region, unlike the hand, is
notably insensitive to high frequency
vibrations and mechanical transients.
Density of sensory afferent endings
more on the oral mucosa
• Oral mucosa mechanoreceptors can be
stimulated by vibrations of adequate
magnitude and frequency in the range
of 0.3–400 Hz (Upadhyay et al., 2016;
Solange et al. 2017).
SMOOTHNESS PERCEPTION

17. Surface profiling of human tongue
1. Polyvinalsiloxane (PVS) was used to obtain the negative mould of the tongue;
2. Gypsum was used to obtain positve mould of the tongue
3. Gypsum mould surface was scanned using a FocalSpec 3D line confocal scanner (accuracy 0.5 m)
4. Moutains Map Software was used to surface profile analysis.
FocalSpec 3D-UULA, Surface Profiler Profile image of a tongue
A negative PVS mould of
human tongue

18. In Situ Oral lubrication measurements
Texture analyser
IOPI pressure sensor
Low friction polly
In situ oral pressure and friction force
Estimated oral friction coefficient

19. CONCLUSIONS
▪ The determining physical priniciples of oral sensation may follow
the transition between the rheology and the tribology
▪ Sensation and perception of oral smoothness, astrigency, and
creaminess are strongly influenced by the oral lubrication
properties
▪ While 0ral lubricity is strongly influenced by food compositions
and structure, complications of saliva and tongue microstructure
must also be taken into consideration

20. Dr.AnaCarolina Mosca
Dr. Solange Sanahuja
ACKNOWLEDGEMENT
20
Dr. Natalia Brossard

21. Thank you for your attention