SRI SRI RAVISHANKAR VIDYA MANDIR

BIOLOGY INVESTIGATORY PROJECT

ESTIMATION OF RELATIVE AMOUNT OF CAFFEINE IN DIFFERENT BRANDS OF TEA

S.PAVITHARA

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ROLL NO. 18

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CERTIFICATE

It is hereby certified that S.PAVITHARA of class XII has satisfactorily completed the Investigatory Project in the subject of Biology on the topic “ESTIMATION OF RELATIVE AMOUNT OF CAFFEINE IN DIFFERENT BRANDS OF TEA” in the

school laboratory.

The work carried out to investigate about the subject matter and the related data collection is original and genuine and has been completed solely and

satisfactorily by the student.

SIGNATURE of TEACHER

SIGNATURE of PRINCIPAL

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ACKNOWLEDGEMENT

I would like to express my gratitude to my teacher Mrs.LEENA SINGH as well as the principal of my institution Mrs.MAMATHA RAVIPRAKASH who gave me the golden opportunity to carry out this wonderful project on the topic ‘Estimation

Of Relative Amount Of Caffeine In Different Brands Of Tea’ through which I learnt many things. I am very thankful to them.

Secondly, I would also like to thank our Lab assistants Mr.DINESH and Mr.GURURAJ who provided me with the facilities and conductive conditions required for on-time completion of this Project. I also would like to thank my

parents and friends who helped me a lot in finalizing and completing this project within the limited time frame. The errors and inconsistencies, if any,

remain my own.

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CONTENTS

SL.NO TITLE PAGE NO.

1 CERTIFICATE 1

2 ACKNOWLEDGEMENT 2

3 INTRODUCTION 4

4 AIM OF THE PROJECT 6

5 APPARATUS 6

6 PRINCIPLE 6

7 PROCEDURE 7

8 OBSERVATION 10

9 RESULT 10

10 INFERENCE 10

11 REFERENCES 11

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INTRODUCTION

Tea (Thea sinensis) is the most commonly and widely used soft beverage in the household. It acts as a stimulant for central nervous system and skeletal muscles and therefore removes fatigue, tiredness and headache. It also increases the capacity of thinking. It is also used for

lowering body temperature. The principal constituent of tea, which is responsible for all these properties, is the alkaloid-caffeine. The amount of caffeine in tea leaves varies from

sample to sample.

The most important methylated alkaloid that occurs naturally is caffeine. Its molecular formula is C8H 10 N4O2 Its IUPAC name is 1, 3, 7-trimethylxanthene and common name is 1-methylated

thiobromine. Purely it is white, crystalline solid in the form of needles. Its melting point is 1230°C.

PROPERTIES OF CAFFEINE It is a bitter alkaloid. It is psycho – stimulant. It improves physical and mental ability. Its effect in learning is doubtful but intellectual performance may improve as it has

been used to reduce fatigue or boredom. When administered internally, it stimulates the heart and nervous system. It is a mild diuretic i.e.; it increases urine output. On the contrary their excessive use proves to be hazardous and their long use may

lead to mental retardation, digestion related problems, renal malfunction, nervousness, etc.

Uses of Caffeine: In medicine, it is used to stimulate, central nervous system and to increase flow of

urine. Caffeine has been used to relieve fatigue because of its stimulating effects. But it is

dangerous and one may collapse if not consumes it under certain limit. Caffeine is also used in analgesic tablets, as it is believed to be a pain reliever. It is

also beneficial in migraines.

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FIGURE 1 CAFFEINE MOLECULE

FIGURE 2 CAFFEINE (PURE) POWDER

FIGURE 3 CRSTAL STRUCTURE OF CAFFEINE

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AIM OF THE PROJECT

To estimate the relative amount of caffeine present in various brands of tea.

APPARATUS REQUIRED

BEAKERS BUNSEN BURNER TRIPOD STANDS WIRE GAUZE FUNNEL SEPERATING FUNNEL FILTER PAPER DIGITAL WEIGH BALANCE GLASS ROD SAMPLES OF ATLEAST 2 DIFFERENT BRANDS OF TEA

CHEMICALS

LEAD ACETATE [ ¿¿ ] CHLOROFORM (CHCl3)

PRINCIPLE

Caffeine is the main active principle component of tea leaves.

It is present in tea leaves up to 3% and can be extracted by first boiling the tea leaves with water which dissolves many glycoside compounds in addition to caffeine.

The clear solution is then treated with lead acetate to precipitate the glycoside compounds in the form of lead complex.

The clear filtrate is then boiled and reduced to one third its initial volume. It is later extracted with chloroform because caffeine is more soluble in it than in water. This chloroform extract is later exposed in order to allow evaporation of chloroform.

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PROCEDURE

Take at least two different brands of tea (here, ‘Brooke Bond three roses’ brand and ‘Tetley green tea’ brand are taken).

To 150 ml of water add 50 g of tea leaves, in a beaker. Then heat the beaker to extreme boiling.

Filter the solution and add lead acetate to the filtrate, leading to the formation of a curdy brown coloured precipitate.

Continue adding lead acetate till no more precipitate has been formed. Again filter the solution. The filtrate so obtained is heated until it has become 50 ml. allow it to cool Add 20 ml of chloroform to the filtrate. Two layers appear. Separate the lower layer using a separating funnel. Expose the solution to the atmosphere in order to allow the chloroform to get evaporated. The residue left behind is caffeine. Weigh the residue. Perform the above procedure with different samples of tea leaves and observe the quantity

of caffeine in them. Tabulate your observations. The relative (percentage) amount of caffeine present in a given tea sample is calculated

using the formula:

Weight of caffeineInitial weight of tea sample

×100

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FIGURE 4-SAMPLE OF GREEN TEA UEDS: TETLEY GREEN TEA

FIGURE 5-SAMPLE OF RED LABEL TEA USED: BROOKE BOND 3 ROSES

FIGURE 6- BOILING OF TEA LEAVES

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FIGURE 7- CURDY BROWN PRECIPITATE FORMED AFTER ADDING LEAD ACETATE

FIGURE 8-THE PRECIPITATED MIXTURE IS FILTERED

FIGURE 9- THE FILTERED MIXTURE IS BOILED

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OBSERVATIONS

SL NO BRAND OF TEA SAMPLE INITIAL WEIGHT OF TEA SAMPLE

WEIGHT OF CAFFEINE OBTAINED

PERCENTAGE OF CAFFEINE PRESENT

1 Brooke bond 3 Roses(Red Label)

20.65 g 0.615 g 2.978%

2 Brooke bond 3 Roses(Red Label)

21 g 0.629 g 2.995%

3 Tetley Green Tea(Green Label)

16.50 g 0.32 g 1.99%

4 Tetley Green Tea(Green Label)

19 g 0.38 g 2%

RESULT

THE AVERAGE AMOUNT OF CAFFEINE PRESENT IN

A. Red label tea : 2.987%B. Green label tea : 1.995%

THEREFORE, RED LABEL TEA CONTAINS APPRECIABLE AMOUNT OF CAFFEINE, SLIGHTLY MORE THAN GREEN LABEL TEA.

INFERENCE

The results obtained are affirmative. Both the brands of tea tested positive for caffeine. Comparision between the brands revealed that Brooke bond 3 roses (red label) contained slightly higher levels of caffeine which may be responsible for better enhanced flavour and is comparatively a better energy provider. However, Tetley green tea (green label) also gave satisfactory results.

To avoid adverse effects tea with optimal amount of caffeine should be considered.

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REFERENCES

Books

Together with Biology Lab Manual Class 12 Exploring Biology for Medical Entrances by Sudhakar Banerjee and Sanjay Sharma NCERT Biology Class 12

Web

Wikipedia https://en.wikipedia.org/wiki/Caffeine icbse.com projects.icbse.com › Chemistry Google Images

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