1. Food Quality Evaluation Methods (FQEM)
University of Kurdistan
Food Quality Evaluation Methods (FQEM)
Lecture 6: Sensory Evaluation
Instructor:
Kaveh Mollazade, Ph.D.
Department of Biosystems Engineering, Faculty of Agriculture, University of Kurdistan, Sanandaj, IRAN.

2. This lecture will cover:
Contents
This lecture will cover:
An introduction to sensory evaluation
How do we taste?
How do we smell?
Sensory evaluation methods
© Institute of Food Technologists 1

3. What is sensory evaluation?
“A scientific discipline used to evoke, measure, analyze, and interpret those responses to products that are perceived by the senses of sight, smell, touch, taste and hearing.”
© Institute of Food Technologists 2

4. How is sensory evaluation used?
In a food company, sensory scientists work closely with product developer’s to understand:
What consumers like and why.
If consumers can tell a difference when they change a product.
In academia, sensory scientists:
Try to understand how our senses work and how our senses respond to stimuli (both from food and chemicals).
Improve testing methodology.
© Institute of Food Technologists 3

5. Why is sensory evaluation used?
It reduces uncertainty and risks in decision making.
It ensures a cost-efficient delivery of new products with high consumer acceptability.
Human observers are good measuring instruments.
People can sometimes detect odorants at levels lower than what can be detected by an instrument.
Instruments can not measure liking.
© Institute of Food Technologists 4

6. How do our senses work? 5 There are five senses:
Taste
Smell
Touch
Sight
Sound
All senses are important when eating.
© Institute of Food Technologists 5

7. Food acceptability
When humans eat, they use all of their senses (sight, hearing, smell, touch and taste) to form general judgments about their food, but it is taste that is the most influential in determining how delicious a food is. 6

8. How does taste work? 7 There are five basic tastes: Sweet Sour Salty
Bitter
Umami
A loanword from the Japanese (うま味?), umami can be translated as "pleasant savory taste". This particular writing was chosen by Japanese chemist Kikunae Ikeda from umai (うまい) "delicious" and mi (味) "taste".
People taste umami through receptors specific to glutamate. Glutamate is widely present in savory foods, such as meat broths and fermented products, and commonly added to some foods in the form of monosodium glutamate (MSG). Since umami has its own receptors rather than arising out of a combination of the traditionally recognized taste receptors, scientists now consider umami to be a distinct taste.
© Institute of Food Technologists 7

9. How do we taste? 8 Taste Map
All qualities of taste can be elicited from all the regions of the tongue that contain taste buds.
Taste researchers have known for many years that the taste map is wrong.
© Institute of Food Technologists 8

10. How do we taste? 9 The tongue has four types of papillae:
Filliform (no taste buds)
Circumvallate
Foliate
Fungiform
Chandrashekar J, Hoon MA, Ryba NJ, Zuker CS
The Receptors and Cells for Mammalian Taste. Nature. 444:
© Institute of Food Technologists 9

11. How do we taste?
The fungiform, foliate, and circumvallate papillae contain many taste buds.
Each taste bud contains taste receptor cells (TRCs).
TRCs project microvillae to the surface of the taste bud, where they form the taste pore; the taste pore is in contact with the fluid portion of food within the mouth.
Taste molecules from food are believed to bind to hair-like cilia that project from the top of the taste cells.
© Institute of Food Technologists 10

12. How do we taste?
After the tastants bind to the cell, the next step, taste transduction is somewhat different for each of the basic tastes.
The chemicals that produce salty and sour tastes act directly through ion channels, whereas those responsible for sweet, umami, and bitter tastes bind to surface receptors that trigger a series of signals to the cells' interiors that ultimately results in the opening and closing of ion channels.
The opening of the ion channels increases the concentration of positive ions inside taste cells - this depolarization causes the taste cells to release tiny packets of chemical signals called neurotransmitters, which prompt neurons connected to the taste cells to relay electrical messages to the brain.
© Institute of Food Technologists 11

13. Some cool things about taste: The trigeminal sense
The nose and mouth are vastly innervated by the trigeminal nerve, including fungiform papillae!
Many food components stimulate these nerve endings and have irritative aspects:
Sting from horseradish and mustards
Burn of chili peppers
Tingle from carbon dioxide
Numbing from menthol
These compounds have long-lasting time properties.
They can cause defensive physical reactions (e.g., salivation, tearing).
They have desensitizing properties – meaning they reduce the sensitivity to stimuli and result in a delayed ability to recover full sensitivity.
St Joseph’s Gamma Knife Center:
© Institute of Food Technologists 12

14. Some cool things about taste: Adaptation
Adaptation is a decrease in response under conditions of constant stimulation.
Taste adaptation is seen with a stable stimulus.
Example: When drinking a beverage the first sip will be perceived as sweeter than the last because you adapt to the sweetness.
While similar to desensitization from trigeminal irritants, recovery from adaptation is much faster.
© Institute of Food Technologists 13

15. Some cool things about taste: Context effects
Human observers act like measuring instruments that constantly re-calibrate themselves to the expected frame of reference.
Example: How warm (cool) is 5 °C in January? What about in August? In January it will feel pretty warm within the context of the cold days vs. in August it will feel cool within the context of the hot days.
The same phenomena occurs with taste.
© Institute of Food Technologists 14

16. How do we smell?
Most of what we “taste” is actually being sensed by our olfactory cells within the nasal canal.
Remember: taste is only sweet, sour, bitter, umami, and salty.
In contrast to taste, humans can smell hundreds of compounds (for a list visit
Flavor is used to describe the perception of taste and smell together.
© Institute of Food Technologists 15

17. How do we smell?
Odorants can reach the olfactory epithelium by two routes:
Orthonasal olfaction: The detection of an odor through the nostrils by sniffing or inhalation.
Retronasal olfaction: The detection of an odorant when it is released from food in your mouth during chewing, exhalation, or swallowing. During this process, the odorant passes through the posterior nares of the nasopharynx.
Halpern, BP Retronasal and Orthonasal Smelling.
ChemoSense. 6(3). 1-7.
© Institute of Food Technologists 16

18. How do we smell?
Odor molecules bond to olfactory receptors (ORs) which are expressed in olfactory sensory neurons (OSNs) in the nose.
Each odorant bonds to a unique combination of ORs.
Each OSN expresses only one OR type but multiple odorants can bond to a single OR type, while a particular odorant can bond to multiple OR types.
There are about 400 functional OR types.
Different people express different OR types.
Buck L and Axel R A Novel Multigene Family
May encode Odorant Receptors: A Molecular Basis for
Odor Recognition. Cell. 65:
© Institute of Food Technologists 17

19. How do we smell?
When stimulated by odorant binding, the olfactory receptors (ORs) activate an olfactory-specific G protein which is displayed on the surface of the modified cilia that extend from each cell.
The G protein in turn activates adenylyl cyclase. The resulting increase in cyclic AMP opens cyclic-AMP-gated cation channels, thereby allowing an influx of Na+, which depolarizes the olfactory receptor neuron and initiates a nerve impulse that travels along its axon.
Buck L and Axel R A Novel Multigene Family
May encode Odorant Receptors: A Molecular Basis for
Odor Recognition. Cell. 65:
© Institute of Food Technologists 18

20. Illustration by Lydia Kibiuk, Copyright © 1995 Lydia Kibiuk.
How do we smell?
Axon extensions from the olfactory sensory neurons (OSNs) converge onto matching glomeruli in the brain’s olfactory bulb.
This means that the response of each glomerulus is an amplified version of the responses of the subset of individual receptor cells.
Odor information is then relayed to many regions throughout the brain.
Illustration by Lydia Kibiuk, Copyright © 1995 Lydia Kibiuk.
© Institute of Food Technologists 19

21. Compound, Odor Quality, and Frequency of Specific Anosmia
Some interesting things about smell: Individual differences
Compound, Odor Quality, and Frequency of Specific Anosmia
Some people lack or lose the ability to smell. This is called anosmia. This condition may be temporary or permanent. Causes can range from a cold to a brain injury.
Some people can’t smell certain compounds. This is called a specific anosmia. Individual differences in the expression of the several hundred olfactory receptor proteins has been used to explain the variation.
Compound
Odor Quality
Anosmia Frequency
Androstenone
Urinous
50%
4-chloroaniline
Mixed
41%
Isobutyraldehyde
Malty
36%
1,8-cineole
Camphoraceous
33%
pentadecalactone
Musky
31%
Trimethyl amine
Fishy 6%
L-carvone
Minty 3%
© Institute of Food Technologists 20

22. Some interesting things about smell: Individual differences
Did anyone ever tell you that you had a “good nose”?
Differences also exist in how sensitive people are to different odorants. Some people are more sensitive to some odorants than others.
Individual differences in the expression of the several hundred olfactory receptor proteins probably also explain the variation.
© Institute of Food Technologists 21

23. Some interesting things about smell: Adaptation
Adaptation or a decrease in response under conditions of constant stimulation occurs with smell as well as taste.
Example: Ever go into a smelly room and realize later you don’t smell it anymore? Or ever wonder why you can’t smell perfume on yourself?
That’s because you have adapted to the smell. This process prevents your brain from going into sensory overload!
© Institute of Food Technologists 22

24. Principles of good practice
Facilities should be well designed:
White or off-white color
Lighting should be controlled
There should be good ventilation
Samples should be prepared properly:
Temperature should be controlled and the same for all samples
Volume served should be equal for all samples
Samples should be served at equivalent shelf-life or time since cooking/preparation
Experimental design considerations:
Samples should be labeled with random 3-digit codes to avoid bias
Samples should be served in random or counterbalanced order
Counterbalanced order means that if 2 samples are served, half of the subjects receive one sample first and the other half receive the other sample first
Counterbalancing takes into account order effects
© Institute of Food Technologists 23

25. Sensory evaluation methods
Goal is to match the right test with the right question.
Question
Method
Are products different?
Discrimination tests
If products are different, how are they different?
Descriptive analysis
What is the acceptability of a product? Is one product preferred over another?
Affective/Hedonic tests
© Institute of Food Technologists 24

26. Discrimination tests
Basic Question: Are two products different from one another?
Basic Setup:
25-50 panelists
Screened for acuity (keenness or sharpness of perception, i.e. can they smell and taste well?)
Given triangle, duo-trio or paired comparison tests
Analysis is done using tables which compare results to chance – this analysis ensures that the difference was real and not because people chose the correct sample by luck/chance.
Advantage:
Quick and simple
Limitations:
Limited results – only yes they are different or no they are not.
© Institute of Food Technologists 25

27. Discrimination tests 26 342 608 194 A B Reference (B) A B 437 821 976
Question: Are two products different from one another?
342
608
194 A B
Triangle Test: Choose the sample that is most different.
Reference (B) A B
Duo-trio Test: Choose the sample that matches the reference.
437
821
976
759
035 B A
Paired Comparison Test: Which sample is sweeter?
© Institute of Food Technologists 26

28. Descriptive tests
Basic Question: How do products differ in all sensory attributes?
Basic Setup:
8-12 panelists
Screened for acuity
Trained
Asked to rate intensity for all sensory attributes
Analysis is done using a t-test to determine if means are statistically different
Advantage:
Detailed quantitative information
Limitations:
Time consuming
© Institute of Food Technologists 27

29. Descriptive tests
Most food companies have a panel that is trained on each of their products.
To train a panel takes several weeks to months.
There are several different methods of training:
Quantitative Descriptive Analysis
Sensory Spectrum
Flavor Profile
© Institute of Food Technologists 28

30. Descriptive tests 29 Sample Ballot What does trained mean?
It means that the panelists are trained to evaluate products similar to how any instrument would give a reading.
In essence, the panelists are calibrated so that they have an understanding of each attribute and the range of intensity.
For example, a trained panel would be a given a sample of grape juice and would be able to rate the level of turbidity, color, viscosity, etc..
© Institute of Food Technologists 29

31. Descriptive tests
Mean attribute ratings are calculated, statistics is used to determine if the means are significantly different.
The data can be plotted onto graphs – such as the spider plot – to easily compare samples.
In this example three brands of grape juice were compared:
Which is sweeter?
Which has more cooked flavor?
© Institute of Food Technologists 30

32. Consumer acceptance tests
Basic Question: Are the products liked?
Basic Setup:
consumers per test
Screened for product use (Do they buy the product? And how often?)
Asked degree of liking (how much do they like it) and/or preference questions
Advantage:
Provides essential information – Do they like it or not?
Limitations:
May be difficult to get a representative sample of consumers.
© Institute of Food Technologists 31

33. Quartermaster Corp. 9-point hedonic (liking) scale
Consumer acceptance tests
Acceptance tests:
Used to measure how much people like a product.
There are several types of scales that can be used.
Sample Ballot
Taste each product in the order listed. Circle how much you like the product.
The Smiley Scale
(Used with kids)
DISLIKE EXTREMELY 1
DISLIKE VERY MUCH 2
DISLIKE MODERATELY 3
DISLIKE SLIGHTLY 4
NEITHTER LIKE NOR DISLIKE 5
LIKE SLIGHTLY 6
LIKE MODERATELY 7
LIKE VERY MUCH 8
LIKE EXTREMELY 9
Quartermaster Corp. 9-point hedonic (liking) scale
(Most common)
© Institute of Food Technologists 32

34. Taste each product in the order that they are listed.
Consumer acceptance tests
Preference tests:
The “Pepsi Challenge” type of test that is widely used in marketing research.
Used to determine which product is preferred, although people have the option to choose “no preference”.
Sample Ballot
Taste each product in the order that they are listed.
Circle the number of the product that you prefer, all things considered.
no preference
© Institute of Food Technologists 33

35. Kurdistan Nature
Zrebar Lake, Marivan