Colour Analysis Flashcards
What is Colourimetry?
It is the science of measuring colour.
What are the two ways we can define a colour?
We can define it by observation, we is subject to variance between people. We can also define it by using a instrument to measure it and assign it a value.
How can we relate both visual and instrumental observation against each other?
By using colour-ordering systems and colour spaces.
What is the importance of measuring the colour of food?
To determine what effect ingredient, process or storage may have on product colour.
We also need to ensure the consistency of ingredient colour and final product colour.
How is the colour important to the customer?
Customers base 80% of their purchases on visual aesthetics. If the colour doesn’t appeal to them you are most likely losing a sale.
What are some advantages and limitations to using the human eye to observe colour?
advantages would be that we can detect up to 10mil different colours which allows to differentiate slight changes in colour. we can define a colour even if the surface is not flat.
The limitations would be a lack of colour memory, variations and defects in eyesight and the lack of language to describe more complex colours.
What do rods and cones do?
Cone receptors perceive colour where as rods perceive brightness.
What is Tristimulus values?
Tristimulus values are the three signals that we perceive colour as. Two hue signals of Blue-Yellow and Red-Green, one brightness signal.
What three basic methods are there for describing colour?
Verbal
Visual matching
Instrumental methods
How do we differentiate colour?
We separate the colour into three numbers, Hue (colour), Value (Lightness/Darkness) and Chroma (Intensity).
What is the munsell system?
Hue ranges from red to red-purple. (all colours in between like a clock)
value of lightness is 0 - 10, with black being 0.
Chroma is the difference between the colours grey equivalent with a scale to 16 or further (0 = neutral grey).
What is the difference between reflected, absorbed and transmitted.
Reflected is the light that reflects of a surface, if all energy is reflected the material is white. Absorbed light is the energy absorbed by the material, if all energy is absorbed then the material is black. Transmitted light passes through the material entirely but light may scatter inside giving it a colour.
How do you prepare samples for instrumental colourimetry?
Soft foods are pressed flat
Viscous products fill a container and covered with a smooth surface cover without air bubbles
Powders (ensure same particle size) are pressed and covered with optical glass
Granular products - fill dish and smooth to provide large surface area.
Transparent samples are testing on neutral backgrounds.
What are the pros and cons of spectrophotometers and colourimeters?
Spectrophotometers are able to determine the exact wavelength reflectance, however this equipment is expensive and reserved for lab use. Colourimeters are quick, portable, cheaper and easy to use which is good for factory settings. colourimeters provide a numerical number for colours.
How does illuminants have an effect on instrumental measures?
Different illuminants make colours appear differently, so they have been classed.
