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Investigation to analyse some fruit and vegetable juices for the contents present in them.

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Analyzing Fruit and Vegetable Juices


Fruits and vegetables are important components of our diet. We take
fruits in raw state or in the form of juices, while vegetables are
taken in the cooked form or sometimes as juices. Fruits and vegetables
provide us carbohydrates, proteins and various other important organic
compounds. The juices are rich sources of minerals, vitamins and many
micronutrients (calcium, iron etc.) essential for us. For example,
iron deficiency in humans causes anaemia and anaemic persons are
advised to take leafy vegetables e.g. spinach and apples which fills
up the iron deficiency. Vitamin-C deficiency causes scurvy which
results in bleeding of gums. This disease can be cured by taking
plenty of Vitamin-C rich fruits like lemon, orange, guava, amla, etc.
Some fruits like papaya and vegetables like carrot are rich in vitamin
A which is essential for eyes to prevent night blindness. In addition,
the fruits and vegetables , particularly their juices provide instant
energy to children, weak or old persons and patients too, as they can
be digested easily. This clearly shows that the fruits and vegetables
play a vital role in maintaining our good health.

Fruits and vegetables are seasonal and grown in different parts of our
country. They need to be stored for longer period and transported to
different places. It makes necessary for us to find out whether there
is any damage to the useful contents of the fruits and vegetable
during the storage and transportation or due to some preservatives or
other factors and what kind of nutrients, minerals, etc. are present
in their juices. With this idea in mind, the project has been
undertaken.

AIM - To analyse some fruit and vegetable juices for the contents
present in them.

APPARATUS - Test tubes, burner, litmus paper, beaker, tripod stand,
conical flasks, burette, pipette.

CHEMICALS REQUIRED -

1. Fehling's solution A

2. Fehling's solution B

3. Tollen's reagent (Ammoniacal AgNO3)

4. Benedict's solution

5. Iodine solution

6. Chloroform (CHCl3)

7. Concentrated nitric acid (HNO3)

8. Concentrated Sulphuric Acid (H2SO4)

9. Ethyl Alcohol (C2H5OH)

10. Alkaline copper sulphate (CuSO4 + NaOH)

11. Aqueous sodium bicarbonate (NaHCO3)

A. Fruit juices that were analysed :-

(i) Apple

(ii) Coconut

B. Vegetable juices that were analysed :-

(i) Tomato

The various experiments and tests performed under the project gave
qualitative analysis to find the presence of various organic compounds
such as carbohydrates, proteins, fats & oils, carboxylic & hydroxyl &
aldehydic groups in the juices of fruits and vegetables.

THEORY :

1. CARBOHYDRATES

Carbohydrates are chemical compounds of carbon, hydrogen, oxygen with
general formula Cn(H2O)n. They have two or more hydroxyl groups and
one aldehydic/ketonic group.

Identification Tests

A. Fehling's solution Test (given only by reducing carbohydrates)

Fehling's solution is an alkaline solution of copper sulphate
containing sodium potassium tartrate (Rochelle salt) as the complexing
agent.

Being strong reducing agents, aldehydes reduce Fehling solution to red
ppt. of cuprous oxide.

[IMAGE]RCHO + 2Cu2+ + [IMAGE] [IMAGE] + Cu2O + 3H2O

Aldehyde

[IMAGE]

B. Tollen's Reagent Test (given only by reducing sugars)

Tollen's reagent is an ammoniacal solution of silver nitrate and is
prepared by adding NH4OH solution to AgNO3 solution till the ppts. Of
Ag2O first formed just redissolve.

When an aldehyde is heated with Tollen's reagent, the latter is
reduced to metallic silver which deposits on the walls of the test
tube.

[IMAGE]2AgNO3 + 2NH4OH Ag2O + 2NH4NO3 + H2O

Grey ppt.



[IMAGE]Ag2O + 4NH4OH 2[Ag(NH3)2]+[IMAGE] + 3H2O

Tollen's Reagent




C. Benedict's Test (given only by reducing carbohydrates)

Benedict's solution is alkaline solution containing citrate ions as
complexing agent.

Aldehydes, on warming with this solution, give brick red precipitates.

Red ppt.

[IMAGE]RCHO + Cu2+ Cu2O + Oxidation Products

D. Iodine solution test (given only by starch)

Presence of starch is tested with iodine which gives blue-black colour
with starch.

2. FATS AND OILS

Fats, oils and their derivatives found in living system belong to the
class of substance called lipids. These are sparingly soluble in water
but highly soluble in organic solvents. Fats and oils are glycerol
esters of different fatty acids. For example, glyceride of unsaturated
fatty acids like oleic acid [C17H33COOH] are called unsaturated fats
and similarly glyceride of saturated fatty acids like Stearic acid [C17H35COOH]
are called saturated fats. Unsaturated fats can be saturated by
addition of hydrogen. This process is called hydrogenation. These are
excellent sources of energy and fats on oxidation provide about twice
as much as energy as that produced by carbohydrates . Important
sources of fats & carbohydrates are peanuts, coconut, soyabean,
butter, cottonseeds mustard, etc.

Identification Tests

A. Fats and oils have generally low melting points. If a fat is shaken
with either ethanol or chloroform in a dry test tube, it dissolves
giving a clear solution.

B. To the given oil or fat sample , add few crystals of potassium
hydrogen sulphate (KHSO4). After heating, a pungent irritating odour
due to the formation of acrolein confirms the presence of an oil or a
fat.

The oil or fat on heating undergoes hydrolysis to give glycerol and
fatty acids. The glycerol thus produced on strong heating undergoes
dehydration to form acrolein which has irritating smell.

[IMAGE]




[IMAGE] Oil or fat Glycerol + Fatty Acids

CH2OH CH2

[IMAGE]

KHSO4

[IMAGE]

[IMAGE]




[IMAGE][IMAGE][IMAGE][IMAGE] CH2OH CH + 2H2O

CH2OH CHO

3. PROTEINS

Proteins are essential organic compounds for any living system to
build and repair our body. Proteins are main constituents of muscles,
blood, skin, hair and other body parts. Besides carbon, hydrogen and
oxygen, other elements such as nitrogen and sulphur are in proteins.
Proteins are made up of chains of amino acids and are very essential
components of our food. Beans, pulses, fish, meat, milk, cheese, etc.
are rich sources of proteins.

Identification Tests

A. Biuret Test

In this test, proteins when heated with strong alkaline copper
sulphate (blue) give a violet or pink colour.

This test is meant for testing the compounds having having a CONH2
group called peptide linkage. As the proteins contain long chains of
peptide linkages, they give positive biuret test by forming complex
with Cu2+ ions.

B. Xanthoproteic test

To the protein sample, add few drops of conc. HNO3. A yellow
precipitate confirms the presence of proteins.

This test is based upon the formation of yellow coloured aromatic
nitro compounds which are produced by the action of nitric acid on the
benzene rings present in some of the [IMAGE]- amino acids (tyrosine,
phenylamine, etc.) constituting the protein.

4. UNSATURATION

The unsaturation in the organic compounds is due to the presence of
double or triple bonds in its constituent compounds.

Identification test

Sulphuric acid Test

In this test, the compound is taken in a clear test tube and conc. H2SO4
is added carefully dropwise. The contents are carefully shaken. The
unsaturated compound dissolves in conc H2SO4 due to the formation of
alkyl hydrogen sulphate (double bonds break to form single bonds).

[IMAGE]

[IMAGE]

[IMAGE]

[IMAGE]




[IMAGE][IMAGE][IMAGE][IMAGE][IMAGE][IMAGE][IMAGE][IMAGE] C C + H2SO4 C
C

OSO3H



5. HYDROXYL GROUP

The hydroxyl derivatives of the paraffins are termed as alcohols.
These are produced by the replacement of one, two or more hydrogen
atoms of paraffins by the corresponding number of hydroxyl groups.
Alcohols are monohydric, dihydric, trihydric or polhydric depending
upon the number of hydroxyl groups present in them. Alcohol and
hydroxyl compounds are generally liquids and soluble in water because
of the functional group [IMAGE] which is capable of forming hydrogen
bonds.

Identification Tests

A. ESTERIFICATION TEST

Alcohols react with carboxylic acids in presence of a few drops of
conc. H2SO4 as catalyst to form esters. A pleasant fruity smell
indicates the presence of an ester and hence the hydroxyl group.

Carboxylic Acid

Ethyl Alcohol

Ethyl ester

[IMAGE]RCOOH + CH3CH2OH RCOOCH2CH3 + H2O

6. ALDEHYDE GROUP

Identification Tests

A. Fehling's solution Test

Fehling's solution is an alkaline solution of copper sulphate
containing sodium potassium tartrate (Rochelle salt) as the complexing
agent.

Being strong reducing agents, aldehydes reduce Fehling solution to red
ppt. of cuprous oxide.

[IMAGE]RCHO + 2Cu2+ + [IMAGE] [IMAGE] + Cu2O + 3H2O

Aldehyde

[IMAGE]

B. Tollen's Reagent Test

Tollen's reagent is an ammoniacal solution of silver nitrate and is
prepared by adding NH4OH solution to AgNO3 solution till the ppts. Of
Ag2O first formed just redissolve.

When an aldehyde is heated with Tollen's reagent, the latter is
reduced to metallic silver which deposits on the walls of the test
tube.

[IMAGE]2AgNO3 + 2NH4OH Ag2O + 2NH4NO3 + H2O

Grey ppt.



[IMAGE]Ag2O + 4NH4OH 2[Ag(NH3)2]+[IMAGE] + 3H2O

Tollen's Reagent




C. Benedict's Test

Benedict's solution is alkaline solution containing citrate ions as
complexing agent.

Aldehydes, on warming with this solution, give brick red precipitates.

Red ppt.

[IMAGE]RCHO + Cu2+ Cu2O + Oxidation Products

O

7. CARBOXYLIC GROUP

[IMAGE]

[IMAGE]




[IMAGE][IMAGE]The organic compounds containing the carboxyl group ( C
OH) as the functional group are called carboxylic acids. Acids
containing one COOH group are termed monocarboxylic acids while others
containing two or three COOH groups are called dicarboxylic and
tricarboxylic respectively. These are normally soluble in water having
pungent smell.

Identification tests :

A. Litmus Test

Dissolve a pinch of the organic compound in water in a test tube and
add to it 2-3 drops of the blue litmus solution. If the blue litmus
solution turns red, it shows the presence of a carboxyl group.

B. ESTERIFICATION TEST

Alcohols react with carboxylic acids in presence of a few drops of
conc. H2SO4 as catalyst to form esters. A pleasant fruity smell
indicates the presence of an ester and hence the carboxyl group.

Carboxylic Acid

Ethyl Alcohol

Ethyl ester

[IMAGE]RCOOH + CH3CH2COOH RCOOCH2CH3 + H2O

C. Sodium Bicarbonate test

Dissolve a pinch of the organic compound in water in a test tube . Add
to it a few drops of aqueous NaHCO3 solution. If there is an
effervescence due to the evolution of carbon dioxide, it shows the
presence of a carboxyl group.

[IMAGE]




[IMAGE]RCOOH + NaHCO3 RCOONa +CO2 + H2O

[IMAGE]

[IMAGE]TEST FOR APPLE JUICE

[IMAGE]

1. CARBOHYDRATES

a) Liquid + Fehling's Solution Red ppt. Present

b) Liquid + Ammoniacal AgNO3 Silver mirror Present

c) Liquid + Benedict's solution Brick Red ppt. Present

2. FATS AND OILS

a) Liquid + CHCl3 + H2O Fat ppt. as emulsion Present

b) Liquid + KHSO4 pungent irritating Present

odour

3. PROTEINS

a) Liquid + Alkaline CuSO4 Violet ppt. Present

b) Liquid + conc. HNO3 Yellow ppt. Present

4. UNSATURATION

a) Liquid + H2SO4 Clear solution Unsaturated

5. HYDROXYL GROUP

a) Liquid + C2H5OH+Conc. H2SO4 Fruity Smell Present

6. ALDEHYDE

a) Liquid + Fehling's Solution Red ppt. Present

b) Liquid + Ammoniacal AgNO3 Silver mirror Present

c) Liquid + Benedict's solution Brick Red ppt. Present

7. CARBOXYLIC ACID

a) Liquid + C2H5OH+Conc. H2SO4 Fruity Smell Present

b) Liquid + Blue litmus solution Turns red Present

c) Liquid + NaHCO3 solution Effervescence due Present

to evolution of CO2

[IMAGE]Text Box: S.No. EXPERIMENT OBSERVATION INFERENCE

[IMAGE]

[IMAGE]TEST FOR COCUNUT WATER

[IMAGE]

1. CARBOHYDRATES

a) Liquid + Fehling's Solution Red ppt. Present

b) Liquid + Ammoniacal AgNO3 Silver mirror Present

c) Liquid + Benedict's solution Brick Red ppt. Present

2. FATS AND OILS

a) Liquid + CHCl3 + H2O Fat ppt. as emulsion Present

b) Liquid + KHSO4 pungent irritating Present

odour

3. PROTEINS

a) Liquid + Alkaline CuSO4 No reaction Absent

b) Liquid + conc. HNO3 Yellow ppt. Present

4. UNSATURATION

a) Liquid + H2SO4 Clear solution Unsaturated

5. HYDROXYL GROUP

a) Liquid + C2H5OH+Conc. H2SO4 Fruity Smell Present

6. ALDEHYDE

a) Liquid + Fehling's Solution Red ppt. Present

b) Liquid + Ammoniacal AgNO3 Silver mirror Present

c) Liquid + Benedict's solution Brick Red ppt. Present

7. CARBOXYLIC ACID

a) Liquid + C2H5OH+Conc. H2SO4 Fruity Smell Present

b) Liquid + Blue litmus solution Turns red Present

c) Liquid + NaHCO3 solution Effervescence due Present

to evolution of CO2

[IMAGE]Text Box: S.No. EXPERIMENT OBSERVATION INFERENCE


[IMAGE]TEST FOR TOMATO JUICE

[IMAGE]

1. CARBOHYDRATES

a) Liquid + Fehling's Solution Red ppt. Present

b) Liquid + Ammoniacal AgNO3 Silver mirror Present

c) Liquid + Benedict's solution Brick Red ppt. Present

2. FATS AND OILS

a) Liquid + CHCl3 + H2O No reaction Absent

b) Liquid + KHSO4 No reaction Absent

3. PROTEINS

a) Liquid + Alkaline CuSO4 No reaction Absent

b) Liquid + conc. HNO3 No reaction Absent

4. UNSATURATION

a) Liquid + H2SO4 Clear solution Unsaturated

5. HYDROXYL GROUP

a) Liquid + C2H5OH+Conc. H2SO4 Fruity Smell Present

6. ALDEHYDE

a) Liquid + Fehling's Solution Red ppt. Present

b) Liquid + Ammoniacal AgNO3 Silver mirror Present

c) Liquid + Benedict's solution Brick Red ppt. Present

7. CARBOXYLIC ACID

a) Liquid + C2H5OH+Conc. H2SO4 Fruity Smell Present

b) Liquid + Blue litmus solution Turns red Present

c) Liquid + NaHCO3 solution Effervescence due Present

to evolution of CO2

[IMAGE]Text Box: S.No. EXPERIMENT OBSERVATION INFERENCE


RESULTS

CONTENTS

APPLE JUICE

COCUNUT WATER

TOMATO JUICE

CARBOHYDRATES

YES

YES

YES

PROTEINS

YES

NO

NO

FATS AND OILS

YES

YES

NO

UNSATURATION

YES

YES

YES

HYDROXYL GROUP

YES

YES

YES

ALDEHYDE GROUP

YES

YES

YES

CARBOXYLIC GROUP

YES

YES

YES

CONCLUSION :

After analyzing the fruits and vegetable juices, the following opinion
emerges about the compounds present in them.

CARBOHYDRATES : The carbohydrates are the main constituents of all the
fruits and vegetable juices but are present in varying quantities.

FATS AND OILS : Fats are rarely found in fruits and vegetables. But in
the present study, the two juices (apple and coconut) show the
presence of fats but it is not found in case of tomato.

PROTEINS : Most of the fruits and vegetables contain proteins. In the
present study, the coconut water and tomato juice did not show the
presence of proteins.

UNSATURATION : Since each fruit and vegetable consists of
carbohydrates, fats & proteins, the presence of double or triple bonds
between carbon atoms is must. Therefore, almost all fruits and
vegetables have unsaturated compounds.

HYDROXYL GROUP : This group is present in all the fruits and vegetable
juices. But as compared to fruit juices, this group is present more in
vegetable juices.

ALDEHYDE GROUP : Aldehydes are type of carbohydrates. They are present
in almost all the juices in large or small quantities.

CARBOXYLIC ACID GROUP : It is also present in all the vegetables and
fruit juices.

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