Part 1

Question 1

Why can perception not always be the same as response?

Answer 1

1. Lack of anonymity -> people may thinks something but respond differently to not offend the tester.
2. Distraction -> environmental noises etc.
3. Confusion -> question is not clear
4. Prior Knowledge -> if people know already about the subject they response can get influenced.

Question 2

What are requirements for a correct sensory evaluation?

Answer 2

1. A controlled environment
2. Subjects:
   - if consumer (>50 people)
   - if trained panel (12-30 people)
   - if experts (1 or few)
3. Appropriate hypothesis
4. Large and reproducible samples
5. Correct methodology and appropriate statistical techniques

Question 3

How can one minimize carry-over-effect?

Answer 3

By randomizing samples to each panelist. Rinsing the mouth with water is not sufficient as some residues can persist and influence next sample sensory profile.

Question 4

What are some key factors in a good design for sensory evaluation?

Answer 4

1. 3 digit code
2. single booth
3. comfortable temperature in room
4. lighting or special lighting
5. blinded testing
6. no logo
7. same cups/glasses/etc
8. etc

Question 5

Why can white and red cheddar be different in color?

Answer 5

Because of a coloring agent.

Question 6

What are pigments?

Answer 6

Pigments are chemical compounds in food that absorb a specific wavelength and reflect another wavelength.

Question 7

What are the three definable dimension of color measurement?

Answer 7

1. Hue -> yellow, blue, red etc
2. Value -> lightness/darkness (light blue) etc
3. Chroma -> saturation, how vivid it is

Question 8

What gives heme groups and its derivatives and chlorophyll their color?

Answer 8

The porphyrin rings. The actual color will depend on the metal ion coordinated in the center.

Question 9

Which metal ion does heme group need and how does it bond with the porphyrin ring?

Answer 9

The metal ion is Fe and will form six coordinate bonds. Four with 4 Nitrogen atoms (from porphyrin ring), one with His residue from the protein and one with other acceptors.

Question 10

What does the color of myoglobin depend on?

Answer 10

1. State of oxidation of Fe (Fe 2+ / Fe 3+)
2. The nature of the other acceptor attached to the Fe
3. Heat may induce change in structure of protein attached to Fe

Question 11

What is the color of myoglobin, oxymyoglobin and metmyoglobin, what is attached at the 6th position and what is Fe oxidation state?

Answer 11

1. Myoglobin:
   Color: purple
   6th position: unattached
   Oxidation: Fe 2+
2. Oxymyoglobin:
   Color: Bright red
   6th position: oxygen (O2)
   Oxidation: Fe 2+
3. Metmyoglobin:
   Color: Brown
   6th position: H20 (water)
   Oxidation: Fe 3+

Question 12

How can one maintain the color of the meat pink/purple even if exposed to oxygen?

Answer 12

By using nitrates or nitrites which will attach at 6th position and do not allows oxygen to attach. Not used anymore due to health regulations.

Question 13

What is the spectral locus?

Answer 13

The curved edge of the gamut is called the spectral locus and corresponds to monochromatic light (each point representing a pure hue of a single wavelength),

Question 14

What is the purity value of white light and monochromatic light (red, etc)

Answer 14

White light = 0
Monochromatic light = 1

Question 15

What is the tristimulus colorimeter?

Answer 15

Is a device that mimic human eye and results are display as LAB values.

Question 16

What does L, a and b from LAB represent?

Answer 16

L= lightness (0 = white, 100= black
a= redness/greenness (more ‘+’ more red, more ‘-‘ more green)
b = yellowness/blueness (more ‘+’ more yellow, more ‘-‘ more blue)

Question 17

if change in E is high (like 2) are two colors easy to be distinguished?

Answer 17

Yes

Question 18

What is the Lovibond tintometer?

Answer 18

The Lovibond tintometer method is the international standard for measuring the color of animal and vegetable fats and oils (any product through which light can pass)