group b3 color measurement and starch pasting
DESCRIPTION
this is our group presentation about color measurement and starch pasting experiment on 2 april 2013TRANSCRIPT
THEORY & PRINCIPLE OF COLOR
MEASUREMENT
COLOR??COLOR : the sensation – experienced by individual- radiant energy within –light visible spectrum (400-800 nm) –retina of eye.COLORANT : pigment that is used to color a product.COLORIMETRY : the science of color measurement.
COLOR PERCEPTION
Things required to see color
A light source
object
observer
- normally emits light that appears to be white
- when the light is dispersed by a prism it is seen to be made up to all visible wavelength
A light sources
Object-object modify light
- colorants such pigments or dyes , in the object selectively absorb some wavelengths of the incident light while reflecting or transmitting others
- there are three types of cones shaped receptors sensitive to red , green and blue
-luminosity is the relative sensitivity of the human eye to various wavelength of light
-rod shaped receptors in the eye are responsible for night vision
-cone shaped receptors are responsible for day light and color vision
Observer
Factors different perception
• different direction (angle)• different sizes --> color different e.g small more darker• different background --> different brightness• different observer --> various color• Different material --> solid, liquid
e.g liquid sample more dark• Different cross-sectional of cell holder--> > thick , >
darker
COLOR MEASUREMENT
Things required to see colorTo see color: to measure color:
Light sources
Object
Observers
Light sources
Specimen
Spectrometer
Measuring color
A colorimeter spectrophotometer or spectrophotometer
Color scales
Visual organization of color
Visual organizations of color:-color has a degree of lightness or value- hue is the color from the rainbow or spectrum or colors- colorant can be added or increase the amount of chroma or saturation
Measured color values:-visual methods of specifying color are subjective- measuring color using an instrument gives objective results
Quantification of color
-brightness (lightness, L) light or dark- color tone (hue, H)- saturation (chrome, C) vivid : more vivid, saturated subdued
Amount of green-red (-a to +a)
Amount yellow-or-blue (+b to -b)
The brightness (or lightness,L) based on the amount of light reflected or transmitted.
Color opponent theory
State that the red, green and blue cone responses are re-mixed into opponent coders as they move up the optic nerve to the brain
Importance Of Colour Measurement As A Quality
Control Tool
● Uniform● Specific● Attraction● Providing a colorful identity to products
that would otherwise have little colour
CIE Colour Space or Colour Model
Lightness (*L)
Chroma (*c)
Hue (*h)
● Delta E● difference between two colour samples● show how far apart the two samples are in the colour 'sphere' visually
Tips for selecting the right color management instruments
● Select instruments with good repeatability● Ensure instruments have sufficient
measurement area● Software that goes with the colour
measuring instruments
Observations
Part 1
• Colour measurement of – liquid (distilled water) and
– solid sample (Washington apple)
Average Std. Dev
L 30.27333 1.589727
C 22.69667 3.466588
H 21.73333 0.638148
Table 1: Values of L, C and H for distilled water
Table 2: Values of L, C and H for Washington Apple
Average Std. Dev
L 88.64667 0.005774
C 138.0233 0.005774
H 85.74333 0.005774
Figure 1: CIELAB Colour Space
Part 2
• The effect of target mask size on colour parameters– Sample used: US Enza Jazz apple– Target mask sizes
• 3mm• 11mm• 36mm
Aperture's Size (mm) L C H3 40.408 25.497 39.534
11 52.298 43.046 43.97736 56.195 50.16 44.439
0 5 10 15 20 25 30 35 400
10
20
30
40
50
60
Comparison of L,C and H between different target mask sizes
LCH
Table 3: Value of L, C and H of US Enza Jazz apple using different target mask sizes
Part 3
• Effect of optical path length on colour parameters– Sample used
• DNS Solution
– Thickness of cell holder used• 2mm• 10mm• 20mm
Cell thickness (mm) L C H
2 88.677 137.993 86.091
10 81.545 140.154 77.577
20 76.85 136.319 73.469
Table 4: Value of L, C and H of DNS solution using different thickness of cell holders
0 5 10 15 20 250
20
40
60
80
100
120
140
160
Value of L, C and H of DNS solution using different cell holder thickness
LCH
Part 4
• Effect of pH on the colour values of red cabbage– Sample used
• Red Cabbage
– pH used• 3• 5• 7• 9• 11
pH L C H
3 81.62 39.2967 343.613
5 90.53 13.1133 317.543
7 85.6067 24.5267 171.977
9 95.7667 37.01 107.53
11 96.83 38.0333 103.187
Table 4: Value of L, C and H of red cabbage of different pH
2 3 4 5 6 7 8 9 10 11 120
50
100
150
200
250
300
350
400
Value of L, C and H of red cabbage in different pH
LCH
References• http://www.rpdms.com/cielch/index.html• http://allfreshkosher.com/red-delicious-washington-apples-extra-fancy-xl.
html• http://
www.chem.uiuc.edu/webfunchem/grammoleprob/GramMoleProb2.htm• http://www.arboschwin.com/index.php?page=hr1• http://fitlifestyle.blogspot.com/2011/06/healthier-with-red-cabbage.html
STARCH
• Predominant food reserve substances in plant
• Provides 70-80% of the calories consumed by human.
• Made up from polysaccharide and commonly found in food
Source of starch• Cereal grain seeds
– Corn– Wheat– Rice
• Tubers and Roots– Potato– Tapioca– Arrowroot
• Peas• Sago
Starch
Amylose
Amylopectin
Amylose• Straight-chain glucose polymer• Account 15% - 20% of starch • Connected by α-1,4-glycosidic bonds• Molecular weight ranging from 105-106
Amylopectin• Very highly branched molecule• Much larger size that amylose• Branches of the amylopectin molecules are clustered
and occur as double helix• Glucose units are linked by α-1, 4-glycosidic bonds and
α-1, 6-glycosidic bonds
1
6
Starch granule
• Made up of amylose and amylopectin molecule arranged radially
• contain both crystalline and non-crystalline regions in alternating layer.
• The clustered branches of amylopectin occur as packed double helix
• packing together of double-helical structures forms small crystalline lamellae.
• more dense of starch granule, which alternate with less dense amorphous layers, contain greater amounts of the crystalline lamellae.
2µm
Potato starch granule
Corn starch granule
General Properties of Potato Starch and Corn starch
Starch Granule size, μm
Amylose %
Amylopectin %
Pasting temperature, ⁰C
Viscosity Paste clarity
Fat %
Protein %
Phosphorus %
Potato 5-100 21 79 56-65 Very high Clear 0.1 0.10 0.08
Corn 2-30 28 72 62-80 Medium Opaque 0.8 0.35 0.00
Starch granules contain both linear amyloseand branched amylopectin.
Raw, uncooked starch granules heated in water
Swelling is evident
Some granules have collapsed
Amylose AmylopectinDo not contribute significantly to viscosity
Give viscosity to cooked paste
Do not contribute to gel formation
For formation of gel
Advantages:1. Uses small
sample size2. Short testing time3. Ability to modify
testing conditions
Rapid Visco Analyser (RVA) indicates starch viscosity by measuring the resistance of flour and water slurry to the stirring action of a paddle.
RELEVANT OF PASTING PARAMETERS TO PROCESSING STEPS CONSIDERATION
pasting temperature
• Temperature at initial swelling of starch granule,takes place when suspended in water.
• Heating starch granules in suspension in water cause water penetrates the granules to hydrate them and resulting swelling.
• provide indication of minimum temperature required to cook.
peak viscosity
• the highest viscosity reached during gelatinization of starch
• occurs prior to the initiation of sample cooling• indicate water binding capacity of starch
breakdown viscosity
• rate of breakdown in viscosity to a holding strength, hot paste viscosity or trough.
• depend on temperature and degree of mixing or shear rate applied to the mixture and the nature of material.
final viscosity
• the increase in viscosity during cooling of paste.
• a measure of retrogradation due to reassociation of the starch molecules
setback viscosity
• reassociation between starch molecules during cooling.
• involve retrogradationor re-ordering of the starch molecules and has been correlated with texture of various products.
DIFFERENCE IN PASTING PARAMETERS FOR CORN STARCH
AND POTATO STARCH
peak viscosity
Pasting temperature
breakdown
Peak temperature
Holding strength
Total setback
pasting curve for potato starch
peak viscosity
Pasting temperature
breakdown
Holding strength
Peak temperature
Total setback
pasting curve for corn starch
potato starch
corn starch
potato starch
corn starch
• pasting temperature of corn starch higher than potato starch. It is about 63.5°C for potato starch and about 75.05°C for cornstarch.
• larger granules gelatinizing at lower temperature and swelling more rapidly than small ones.
•peak viscosity for potato starch is 6069 cP and for corn starch is 2899cP.
•potato starch granules are much larger and, as a result, swell more easily.
• Large starch granules tend to build higher viscosity
•breakdown viscosity for cornstarch is lower than potato starch. for corn starch it is 1037 and for potato starch it is 4237.
•Viscosity break-down is the result of the molecule chain lengths being broken caused by heat.
•The larger size of granule,the less molecular bonding so it will breakdown faster.
• final viscosity of cornstarch is slightly higher than potato starch.
• due to higher amylose content in corn starch compared to potato starch.
• corn starch has a higher setback value compared to potato starch
• the amylose in corn starch reassociate more readily.
• retrogradation occurs due to association of linear amylose molecules, which can give rise to “setback”.