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Quality Characteristics of Food (Colour (measured by quality and research…
Quality Characteristics of Food
Texture
physical attribute of food based on tactile senses
measured objectively by mass, time, distance
Brookfield viscometer -> measures fluid viscosity at given shear rate
Newtonian foods -> viscosity independent of shear rate (water, milk, oil)
penetrometer and hand held pressure tester -> measure hardness of substance by measuring depth or rate of penetration of rod
Texture analyser -> quantitative data based on force, distance and time which can be interpreted as hardness, fracturability, break strength, firmness
textural parameter of food: hardness, adhesive, cohesive (brittleness, chewiness, gumminess), viscous, elastic, plastic
Non-Newtonian foods -> rheopectic and thixotropic (change viscosity over time with shear stress)
trained human sensory panels
Colour
measured by quality and research development
by visual inspection - human, colour measuring instrument, computer image analysis technique
measure colour: lightness, hues, saturation
Wavelength that reflect an object is what we process as colour -> different colours associated with different wavelengths
BYK Gardner Spectro guide spectrophotometer -> measures colour and gloss
Spectrophotometer -> measures colour absorbance at given wavelength -> highest absorbance indicates the wavelength that is absorbed in object and not perceived by eyes, provides absorbance spectral curve, quantitative measurement of the absorbance of a material as a function of wavelength, measures absorbance of light by measuring intensity of light beam of light passes through sample solution, measurement of how much object transmits/absorbs wavelength
factors that affect how you perceive colour: ability to see, distance, environment, light source, surface (texture), movement, gloss
CIE L
a
b* colour space is mathematically derived from X Y Z values and based on Hunter tristimulus data
L* = lightness (0=black & 100=white)
acceptable: sample - standard = colour difference
measurement of colour: calibration, sample preparation, rad at optical thickness, standard light source, correct illuminant, ambient controlled conditions (temperature, humidity, sample temperature)