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Transcript of Poly Phenol
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Form 6 Chemistry Project
Analysis of Polyphenol Content in Tea
6B Chan Wai Yin (2)
6B Cheung Lok Chun (4)
6B Yuen Tik Wan (15)
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Part 1
Introduction
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Introduction - Tea
nAn aromatic beverage
prepared from tea
leavesn Tea leaves are
collected from tea
bush
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Introduction History of Tea
n China has the first
tea-drinking record in
human historyn Discovered by
Shennong () in2737 B.C.
n Tea-tradingintroduced tea to the
whole worldCha Jing () by Lu Yu() in Tang Dynasty
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Introduction Classification of
Tea
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Introduction Tea Culture
Chinese Tea Ceremony
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Introduction Tea Culture
Japanese Tea Ceremony Korean Tea Ceremony
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Introduction Polyphenols
n Polyphenols are refering
to a large group of
chemicals
n Polyphenols are definedas compounds containing
more than one phenol
group per molecule
n They are long-chainpolymers
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Introduction Polyphenols
n Can be further dividedinto a number ofsubgroups
n Examples: tannic acid,lignin
n Teas is rich inpolyphenols, up to 25%of dry weight
n Polyphenols in teas arealso refered as catechin()
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Introduction Health Claims of
Polyphenols
n Counteracting free radicals, the main cause ofaging
n Reducing the risk ofn Cardiovascular disease
n Cancers
n Food poisoning
n Diabetes
n Stress-related mental diseases
n Probably, helping lose weight
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Introduction Aim
n In order to obtain as much polyphenols
from tea as possible, we would like to find
outn The species of tea possessing the largest
amount of polyphenols
n
The best tea-drinking habit of alln Whether all kinds of plants are suitable for
making tea
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Introduction Method of Bisection
n React polyphenols with sodium hydroxide
(NaOH) solution
nAdd concentrated iron(III) chloride (FeCl3)solution into the mixture
n If polyphenols are in excess, blue colour will
be shownn If sodium hydroxide is in excess, precipitation
will occur
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Introduction Method of Bisection
Mixing and adding FeCl3
Blue colourPrecipitate Equilibrium
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Introduction Method of Bisection
Precipitate
Blue colour
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Introduction Method of Bisection
Where
n Mp = concentration of polyphenoln Mn = concentration of sodium hydroxide solution
n Vn = volume of sodium hydroxide solution
n Vt = volume of tea
= 7 Vt
Mn Vn
Mp
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Part 2
Design of Experiments
E i t 1
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Experiment 1:
Best Species
Aim: Finding the species of tea containingthe largest amount of polyphenols.
Method: Boil 1g of different tea leaves with250ml distilled water under 80oC for5minutes.
Then use bisection method to find out theratio of tea to NaOH.
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Problem
The tip of burette was
blocked by the
residue.
If we use filter paper,
the time of soaking
will be affected.
E i t 2
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Experiment 2:
Optimum temperature
Aim: Finding the optimum temperature for
the release of the largest amount of
polyphenols.
Method: Using 250ml of distilled water to
boil 1g of tea leaves under0oC, roomtemperature, 70oC, 80oC &100oC.
E i t 3
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Experiment 3:
Time of soaking
Aim: Finding the effect of soaking on the
release of polyphenols.
Method: Use 250ml of distilled water to boil
1g of tea under 70 oC for5minutes
intervals until 30minutes.
Experiment 4:
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Experiment 4:
Tea with milk
Aim:Finding the effect of addition of milk onthe concentration of polyphenols.
Method: Adding milk into the chosen tea.Remove the protein and
Special technique: Using HCl to remove theprotein.
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Experiment 5:
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Experiment 5:
Tea powder
Aim: Finding the effect of tea powder on the
release of polyphenols.
Method: Burnish the tea leaves into tea
powder and boil it under the same
condition.
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Tea Powder
Experiment 6:
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Experiment 6:
Wild plants
Aim: Testing different kinds of plants for their
release of polyphenols.
Method: Collect the leaves and boil them with
250ml water at 100oC for 5minutes.
Special technique: Burnish the leaves to increase
the surface area for the releasing of polyphenols.
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Part 3
Results and Conclusion
Result Experiment 1: Best
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Result Experiment 1: Best
Species
Concentration of Polyphenols of Different Species of
Tea
0
0.005
0.01
0.015
0.02
0.025
Species of Tea
Concentrationof
Polyphenols(M
)
Result Experiment 2: Optimum
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Result Experiment 2: Optimum
TemperatureEffect of Water Temperature on Concentration of
Polyphenols
0
0.0020.004
0.006
0.008
0.01
0.012
0.014
0.016
0 20 40 60 80 100 120
Water Temperature (Degree Celsius)
C
oncentrationof
P
olyphenols(M)
Result Experiment 3: Time of
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Result Experiment 3: Time of
Soaking
Effect of Time of Soaking on Concentration of
Polyphenols
0
0.001
0.002
0.003
0.0040.005
0.006
0 10 20 30 40
Time of Soaking (mins)
C
oncentrationof
P
olyphenols(M)
Result Experiment 4: Tea with
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Result Experiment 4: Tea with
Milk
n Experiment Failed because
nAlthough addition of concentrated
hydrochloric acid did coagulate milk protein,the solid protein is still too soft to be filtered
off
n Direct addition of iron(III) chloride (FeCl3)
solution into the mixture of tea and milkshowed NO observable colour change and
precipitation at all
Result Experiment 5: Tea
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Result Experiment 5: Tea
PowderEffect of powdering of concentration of polyphenols
0
0.0005
0.0010.0015
0.002
0.0025
0.003
0.0035
0.004
0.0045
0.005
Original tea leaves Tea powder
ConcentrationofPolyphe
nols(M)
Result Experiment 6: Wild
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Result Experiment 6: Wild
Plants
nAll 4 samples showed no colour change
upon direct addition of iron(III) chloride
(FeCl3) solutionn This indicated extremely low polyphenol
concentration in the samples
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Conclusion
n contains the largest amount of polyphenolsamong all common tea species, while flower
teas tend to contain relatively small amount of
polyphenols
n Best tea-drinking habit
n 80
n Soak for 10 minutesn In powder form
n Most of the plant species are not suitable for
making tea
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Part 4
Q & A Section