poly phenol

7/14/2019 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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Mixing and adding FeCl3

Blue colourPrecipitate Equilibrium


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Precipitate

Blue colour


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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


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


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

poly phenol

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