Instrumental testing methods for sensory qualities of food

1. FOOD QUALITY AND STANDARDS
FT- 507
“INSTRUMENTAL METHODS FOR TESTING SENSORY
QUALITIES ”- ( SIGHT, HEAR & TOUCH)
SUBMITTED BY:
KRATIKA SINGHAM
INT.FOOD TECHNOLOGY

3. TYPES OF ANALYSIS
SUBJECTIVE ANALYSIS / ORGANOLEPTIC
 People oriented- uses individual
 Three divisions- (Effective testing, Affective testing , perception)
 Involves human sensory organs- appearance, flavour, color, texture
 Result may vary
 Determines human sensitivity to changes in ingredients, processing or packaging
 Determine consumer acceptance
 Time consuming and expensive
 Must for product development and for good marketing of new products

4. OBJECTIVE ANALYSIS
• Product oriented
• Uses equipment(Analytical)
• Use physical and chemical technique.
• Results are repeatable.
• Need to find a technique appropriate for the food being tested
• Cannot determine consumer acceptance unless correlated with sensory
testing.
• Generally faster and cheaper and more efficient.
• Essential for routine quality control.
Measures-
 density
 maturity
 moisture content
 oil content
 tenderness ,etc.

5. FOOD SENSES
 TOUCH - TEXTURE , VISCOSITY & CONSISTENCY (SMOOTH, GRITTY, GRAINY,
CHALKY, FIBROUS, LUMPY, BRITTLE, CREAMY, VISCOUS, ELASTIC, STICKY,
SPONGY, SLIPPERY)
 SIGHT- COLOR, &APPEARANCE(GLOSSY, OILY, TRANSPARENT, CLOUDY,
OPAQUE, TRANSLUCENT)
 HEAR- SOUND (CRUNCHY, CRISPY, POPPY, CRACKLY, FIZZ, SQUEAK)

6. TYPES OF TEXTURE MEASUREMENT
Empirical- method measure often ill-defined variables that are
indicated through practical experience to be related to some aspect
of textural quality, and are frequently dedicated to a specific
product type. Eg: penetrometer
Imitative - Imitative methods mimic conditions that the
product is subjected to during eating. Eg:TPA
Fundamental- Fundamental methods measure well-defined
physical properties of the product which can be independent
of the measurement method. Eg: UTM

7. SENSORY- TOUCH
Consistency and Texture& viscosity
 Texture - (for solids or semisolids ) eg: apple, curd, butter
 Viscosity - (for homogeneous Newtonian liquids)
eg: ketchup, honey
 Consistency - (for non-Newtonian or heterogeneous
liquids and semisolids )
eg: mayonnaise, pudding

8. TEXTURE MEASUREMENT
 Universal testing Machine(UTM)
 Snapping –Bending test( 3 point bending test)
 Tenderometer
 Puncture test
 Penetrometer
 Texture profile analysis(TPA)
Dough testing instruments
 Farinograph & Mixgraph
 Extensograph & alveograph
 Amylograph

9. UNIVERSAL TESTING MACHINE (UTM)
A Universal testing machine (UTM) is used to test the mechanical properties
(tension, compression etc) of a given test specimen by exerting tensile,
compressive or transverse stresses. The machine has been named so because
of the wide range of tests it can perform over different kind of materials.

10. COMPONENTS
A universal testing machine consists of two main parts :
(i) Loading unit:-
1. Load Frame
2. Upper Crosshead and Lower Crosshead
3. Elongation Scale.
(ii) Control Unit:-
1. Hydraulic Power Unit
2. Load Measuring Unit
3. Control Devices
PERMORMS:-
• Tensile Test
• Compression Test
• Adhesion Tests
• Pull-Out Tests
• Bending Test
• Hysteresis Test
• Friction Test
• Flexural Test
• Spring Test
APPLICATIONS:
• Firmness
• Crunchiness
• Hardness
• Extendibility
• Brittleness
• Gumminess
• Cohesiveness
• Stickiness

11. 3- POINT BENDING TEST
Working/Mechanism
• First deforms food elastically and then plastically
• If the sample is sufficiently brittle the force required within the limit of the
load cell, fracture will occur
• Unstretched / uncompressed plane is called “neutral surface”

12. During the test, the force applied, the distance moved by the probe and the time
are all recorded in Exponent. The force-distance graph usually begins with a
straight section that corresponds to elastic (reversible) deformation, then most
samples show a curved section that shows plastic (irreversible) deformation

13. TENDEROMETER
Instrument to measure the stage of maturity( harvest) of mostly peas and
tenderness of foods to determine whether they are ready for cropping.
Measures the force required to effect a shearing action.
APPLICATION
Most pea processors pay their growers based on the Tenderometer value of
the peas delivered to the processing plant. A Tenderometer Unit is a direct
measure of the maturity and quality of the raw product being supplied,
analyzed in bulk.

14. PENETROMETER
• A penetrometer is a device to test the strength of a material
• Penetrometers, equipped with a plunger and a needle or
cone, penetrate food samples through gravitational force for a
selected period of time. The distance the test device
penetrates into the sample is measured to determine the
relative tenderness of the samples
APPLICATIONS
 baked products ( pizza bases, bread cakes)
 Gels ( jellies)

15. FARINOGRAPH
The farinograph is a tool used for measuring the shear and viscosity of a mixture of flour
and water Uses- 1) milling (flours)
2) bakery( buiscuits, breads cakes ,tortillas)
Used to determine wheat flour’s(used by bakers mostly)
• Water absorption
• Dough viscosity, including peak water to gluten ratio prior
to gluten breakdown
• Peak mixing time to arrive at desired water/gluten ratio
• The stability of flour under mixing
• The tolerance of a flour's gluten
WORKING
Farinographs measure and record the resistance to deformation of a flour/water dough
against the mixing action of blades over time and at a specific speed (rpm) and
temperature. Dough resistance is expressed as motor torque, in dimensionless units known
as Farinograph or Brabender Units (FU or BU). During the test, the dough is developed and
further broken down.
 Resistance has traditionally been known as “consistency.” The maximum consistency of
the dough is adjusted to a fixed value (500 FU) by altering the quantity of water added
(i.e. % absorption).

16. MIXOGRAPH
• It measures and records resistance of a dough to mixing. It consists of small
dough mixer constructed in such a manner that the force required (torque) to
turn a head over a static bowl containing dough is measured and recorded as a
graphical curve called “mixogram”.
• The wider the curve, the stronger the flour, and the more elastic and less
extensible the dough will be. The steeper or the more pronounced the angle
after peak, the less mixing tolerance.

17. EXTENSOGRAPH
An extensograph is a tool used for measuring the flour quality and stretching behavior of dough.
Extensional properties, which determine the course of dough expansion during proofing and baking,
have a direct effect on:
• Loaf volume
• Quality of texture of bread crumb1
Information on the extensional properties of bread dough is read directly from the diagram of the
extensograph curve, also referred to as the “extensogram” The extensogram represents changes in
resistance, also called the strength, of the dough to extension (R) as a function of the extension
distance.
APPLICATIONS:
 extensograph are useful in determining the gluten strength and bread-making characteristics of
flour.

18. ALVEOGRAPH
An alveograph is a rheological tool used to assess the baking
performance of flours used in baked products (bread, noodles, tortillas,
biscuits, etc.).
WORKING
It is based on injecting air into a thinly stretched sheet of dough to form a
bubble, simulating gas/carbon dioxide release and retention during
dough fermentation and oven spring during baking.
APPLICATIONS
• Bakers use alveograph data to gain understanding of fluctuations in
dough rheological changes by assessing:
• Tenacity
• Elasticity
• Baking strength
• Resistance of dough to deformation
• Extensibility

19. PUNCTURE TEST
Puncture and penetration tests are commonly used in the testing of the ripeness and bio
yield point of fresh fruits and vegetables
USES
 Ripeness of cheese,
 Hardness of confectionery
 Spreadability of butter and margarine.
 rigidity of gels
 Firmness, gel strength, dipping consistency, product toughness, fracture force, 'cake'
breaking strength, semi-solid consistency, actuation force
Penetration tests usually employ cylinders (2mm – 10mm diameter), cones, ball probes or
needles. Small probes are particularly recommended for the assessment of rupture force
or for the testing of multiple structure products e.g. measuring skin/crust/coatings and
continuing to test the underlying material.
• Ball probes are recommended where the surface of the sample is not flat or the
sample is extremely thin.
• Hemispherical probes are recommended for imitating a finger when assessing
actuation force.
APPLICATIONS:
• Texture of fish gels

20. TEXTURE PROFILE ANALYSIS (TPA)/ TEXTUROMETER
 Texture profile analysis(TPA) compresses a bite-sized piece of food usually (1cm cube) twice to
stimulate the chewing action of the teeth.
 Compression is usually 80% of the original length of sample.
 Texture analyzer are used to obtain” texture profile analysis”
 The force curve generated as a function of time is called “Texture profile”
PRINCIPLE
Texture measurement system is physically deforming a test sample in a controlled manner and
measuring its response.
WORKING
A Texture Analyzer is a texture measurement system that moves up or down to compress and stretch a
sample. In a simple test, the analyzer's traveling arm is fitted with a load cell. It records the force
response of the sample to the deformation that it is undergoing.
Since the instrument compresses the sample twice , two positive and two negative curve are obtained
. Peak forces and areas under the curves are used to
Determine various properties of foods like –
 Fracturability (brittleness)
 Hardness
 Cohesiveness
 Adhesiveness
 Springiness(elasticity)
 Gumminess
 Chewiness

21. • Fracturability- defined as the force at the first significant break in the first positive bite
area
• Hardness- defined as the peak force during the first compression cycle
• Cohesiveness- is defined as the ratio of the second positive bite area to the first
positive bite area
• Adhesivenss- is defined as the negative force area for the first bite representing the
work required to pull the plunger away from the food
• Springiness (elasticity) - is defined as the height to which the food recovers during the
time that elapses between the end of the first bite and start of the second bite (
distance or length of the compression cycle during the second bite)
• Gumminess- defined as the product of hardness and cohesivess . In sensory terms, it is
the energy required to disintegrate the semi solid food so that it is ready for
swallowing.
• Chewiness- is defined as the product of gumminess and springiness. In sensory terms it
is known as the energy required for chewing a solid food until it is ready for swallowing

22. TPA CURVE
ADAVNTAGES
 A texture analyzer has the capacity to replace human sensory evaluation by providing a
numerical value that can serve as a quality assurance standard when evaluation products.
 Additionally an instrumental method of assessing texture can be carried out under strictly
defined and controlled conditions that are repeatable.
 Your texture measurement test method or application will call for different levels of
technology, accuracy, load capacity and budget.

23.  Cone probes
 Cylinder probes
 Round end probe
 Puncture probe
 Knife/shear probes
 Grisp + clamp probes
 Extrusion fixtures
 Food fixtures

24. SENSE - SIGHT
SIGHT
• The human eye has an important role in the perception of colour, and this influences
our idea of food flavour.
• Research shows that we associate specific colour perception of food with certain
flavours (although tastes like bitter and sweet are not associated with a particular
colour). The stronger the flavour/colour link, the greater the impact of food colour.
As colour levels increase our perception of taste and intensity of flavour do also.
COLOR
A phenomenon that involves both physical and psychological components: the
perception by the visual system of light of wavelengths 400 to 500 nm (blue), 500 to 600
nm (green and yellow), and 600 to 800 nm (red), commonly expressed in terms of the
hue, value, and chroma of the Munsell color system. Deterioration of food is often
accompanied by a color change.

25. COLOR MEASURING INSTRUMENTS
• Spectrophotometer
• Colorimeter
• Hunter lab
Color order system
1. Munsell color system
2. CIE color system
3. CIE l*a*b (CIE LAB) color spaces
4. Hunterlab color space
5. Lovibond system
6. Color differences

26. SPECTROPHOTOMETER
The spectrometer is to produce light of any wavelength, while the photometer is to measure the intensity of
light. The spectrophotometer is designed in a way that the liquid or a sample is placed between spectrometer
and photometer.
photometer measures the amount of light that passes through the sample and delivers a voltage signal to the
display. If the absorbing of light change, the voltage signal also changes.
PRINCIPLE
Spectrometer- produce light from any selected wave length
Photometer- measures the intensity of light, and the analyte is put between them
Beer’s Law
This law states that the amount of light absorbed is directly proportional to the concentration of the solute in
the solution.
Log10 I0/It = asc
where,
as = Absorbency index
c = Concentration of Solution
Lambert’s Law
The Lambert’s law states that the amount of light absorbed is directly proportional to the length and thickness
of the solution under analysis.
A = log10 I0/It = asb
Where,
A = Absorbance of test
as = Absorbance of standard
b = length / thickness of the solution

27. COMPONENTS
 Light source
 Monochromator .
 Sample holder
 Beam splitter
 Mirror
 Photodetector system
 Measuring device
APPLICATIONS
 The spectrophotometer is commonly used for the determination of the concentration of
colored as well as colorless compounds by measuring the optical density or its absorbance.
Eg: fruit juices, beverages
 It can also be used for the determination of the course of the reaction by measuring the rate
of formation and disappearance of the light absorbing compound in the range of the visible
& UV region of electromagnetic spectrum.
 A compound can be identified by determining the absorption spectrum in the visible region
of the light spectrum as well as the UV region of the electromagnetic spectrum.

28. TYPES OF SPECTROPHOTOMETER

29. COLORIMETER
• Colorimeter is the instrument which is used in the measuremnent of the
luminous intensity of light
• It is the most common analytical technique used in biochemical estimation
• Involves quantitative estimation of color
• A substance to be estimated must be colored or capable of forming
chromogens through the addition of reagent.
• The color of light is the function of its wavelength
PRINCIPLE
When a monochromatic light passes through a colored solution , some specific
wavelengths of light are absorbed which is related to color intensity. The amount
of light absorbed or transmitted by a color solution is in the accordance with two
laws beer’s and lambert’s law according to which the absorption of light
transmitted through the medium is directly proportional to the medium
concentration

30. COMPONENTS
• Tungsten lamp
• Slit
• Condensing lens
• Cuvette
• Filter
• Photocell
• Galvanometer

31. APPLICATIONS
For the Estimation of:
 Glucose
 Urea
 Creatinine
 Water quality
 Uric acid
 Bilirubin
 Lipids
 Total protein
 Enzymes ( ALT, AST, ALP)
 Minerals( calcium, phosphorous)
ADVANTAGES
• It is an inexpensive method,
• widely used in the quantitative analysis of coloured samples,
• easy to carry and transport.
DISADVANTAGES
• Analysis of colourless compounds is not possible
• Does not work in IR and UV regions.
• We cannot set specific wavelength as we have to set a range as a parameter
• Similar colors from interfering substances can produce errors in result.

32. HUNTER LAB
Based on the basic of the opponent-color theory which assumes that the receptors in the
human eye perceive color as the following pairs of opposites: Light-dark , Red-green ,
Yellow-blue. All three values are required to completely describe an object's color.
The Hunter L, a, b color space is a three dimensional rectangular, where:
• L (lightness) varies from 0 (black) to 100 (white),
• a which represent red-green axis with positive (redness) and negative (greenness)
values
• b which represent yellow-blue axis with positive (yellowness) and negative (blueness)
values.
• The values of 0 for the a* and b* always represent neutral.
• Once the L, a, b position of a standard color is determined, a rectangular tolerance box
can be drawn around the standard.
• There are two popular L, a, b color scales which
are Hunter L, a, b and
• CIE L*, a*, b*.
• Hunter L, a, b is over expanded in the blue region
of color space whereas CIE L*, a* and b*
is over expanded in the yellow region.

33. MUNSELL- COLOR ORDER SYSTEM
The Munsell color-order system is a way of specifying colors and showing the
relationships among them. Every color has three qualities or attributes: hue,
value, and chroma. Munsell established numeric scales with visually uniform
steps for each of these attributes. The color of any surface can be identified by
comparing it to the chips under proper illumination and viewing conditions. The
color is then identified by its hue, value, and chroma

34. SENSE- HEAR
• Being able to hear the sounds of food contributes
to the enjoyment of eating – not just the crackle
and crunch as we eat but also the sizzle and spit
of the cooking process.
• Hearing sounds contributes to the experience of
eating crisp and crunchy foods like potato chips
and biscuits.

35. SOUND – A HIDDEN SENSORY ATTRIBUTE
• When a crisp food is broken or crushed characteristic sounds are produced
due to the brittle fracture of the cell walls. Since cracks propagate at very
high speeds (too high for even high speed cameras) the sound is produced in
a very short space of time – i.e. as a pulse. Slowed down and plotted onto a
graph, the pulses can be seen as a series of tall peaks, but actually last only
for milliseconds. The more peaks, the crispier it is – it's as simple as
that. These sounds (acoustic emission) have been used to try to quantify
sensory crispness.
• Crisper products would produce louder noise
• Amplitude is one of the variables that distinguishes more crisp from less crisp
sounds. This is used in combination with the number of sounds (frequency)
produced within a given distance or time.

36. COMMON NOISE CHARACTERSTICS OF FOODS
 PITCH - frequency of sound, Crispy, Crunchy, Squeak
 LOUDNESS- intensity of sound
 PERSISTENCE- endurance of sound over time, Perceived sounds (pitch,
loudness, persistence) and auditory measurement
MEASURING OTHER SOUNDS
 The ‘Crack’ of a chocolate coating (whilst measuring the force to
crack)
 The ‘Snap’ of spaghetti (whilst measuring the break)
 The ‘Squeak’ of Halloumi cheese (whilst measuring the bite force)
 The ‘Bite’ of an apple (whilst measuring the force to puncture its skin)

37. TEXTURE ANALYSER
Texture Analyser using an appropriate fixture – eg: for a biscuit, use a three-
point-bending rig. They would then position the microphone 1 centimetre from
where the biscuits were going to fracture. The acoustic data would then be
captured throughout the breaking of the biscuit and would be presented
graphically, as a jagged line with some taller peaks.

38. ISO STANDARDS FOR SENSORY ANALYSIS
• ISO 3591-1977 Sensory analysis - Apparatus - Wine-tasting glass
• ISO 3972-1991 Sensory analysis - Methodology - Method of investigating
sensitivity of taste
• ISO 4120-1983 Sensory analysis - Methodology - Triangular test
• ISO 4121-1987 Sensory analysis - Methodology - Evaluation of food
products by methods using scales
• ISO 5495-1983 Sensory analysis - Methodology - Paired comparison test
• ISO 6564-1985 Sensory analysis - Methodology - Flavour profile methods
• ISO 10399-1991 Sensory analysis - Methodology - Duo-trio test
• ISO 11036-1994 Sensory analysis - Methodology - Texture profile
• ISO 11037-1999 Sensory analysis - General guidance and test method for
assessment of the colour of foods
• ISO 11056-1999 Sensory analysis - Methodology - Magnitude estimation
method