DAV PUBLIC SCHOOL HUDCO, BHILAI

SESSION: 2025-2026

CHEMISTRY INVESTIGATORY PROJECT

A
Project Report
On
“Study digestion of starch by salivary amylase and effect of pH and
temperature on it”

Submitted By- Guided By-

Bhavya Nema Mrs. Ruchi Priya
Class - 12th A
 ACKNOWLEDGEMENT

I would like to express my sincere gratitude and thanks to

my English teacher Mrs. Ruchi Priya mam for her vital
support, guidance and encouragement for completion of my
Investigatory project on the topic “Study the digestion of
starch by salivary amylase and the effect of pH and
temperatures on it”.
Without her support this project would have not come
forth.

I would also like to extend my sincere gratitude to our

respected Principal sir Mr. Prashant Kumar for providing me
support for this project.
Date: 20/06/2025
 CERTIFICATE OF COMPLETION

This is to certify that Bhavya Nema student of Class 12th- A,

DAV Public School has completed his investigatory project
on “Study the digestion of starch by salivary amylase and
the effect of pH and temperatures on it” under the
guidance of Mrs. Ruchi Priya mam during the academic
year of 2025-2026 towards the partial fulfilment of credit
for “Chemistry (043) Practical” evaluation of CBSE and
submitted satisfactory report, as compiled in following
pages.

INTERNAL EXTERNAL PRINCIPAL

 CONTENTS

 Aim
 Requirements
 Introduction
 Theory
 Procedure
 Observation
 Results
 Precautions
 Bibliography
 AIM
To study the digestion of starch by salivary amylase and the
effect of pH and temperatures on it.

Requirements: -
 Test tubes
 Test tube stands
 Measuring cylinder
 Sodium chloride
 Distilled Water
 Iodine Solution
 Iodine
 Burner
 Pipettes
 Starch
 Beakers
 Funnel
 Cotton
 INTRODUCTION

 Salivary gland present in mouth secret saliva. The saliva

contains much to lubricate food and a starch digestion
enzyme – Salivary amylase.
 Salivary amylase acts as starch a polysaccharide and
changes it into simple sugars.
 The enzymes are not active at temperatures 37°C and at
pH 6.8.
 Like other enzymes salivary amylase is also
proteinaceous. It is denoted by head and chemicals like
alcohol. Thereby making it inactive permanently.
 When iodine solution(yellow) is added to starch
solution, then later turns to blue, black. Iodine does not
react with simple sugars, hence remains yellow.
 If saliva is added to blue-black solution the enzymes,
salivary amylase present in saliva breaks down starch
and the colour and the Colour of sodium changes for
blue -black to reddish brown and then to its original
yellow colour.
 The complete breakdown of starch into simple sugars
can be tested by adding Benedict’s solution to the X
mixture and heating the solution. The colour of solution
will change from-
Blue to green to yellow to orange.
Indicating the presence of simple sugar and absence of
starch in the solution.

STARCH + WATER = MALTOSE

 PREPERATION

 1% Starch Solution
To 10ml of distilled water add 1g of Solution starch to
make it into a thick paste Boil 90 ml of distilled water
and to it add 10ml of the starch paste already prepared,
gradually by stirring. Leave the solution overnight and
filter to get 1% Starch solution.
 1% NaCl Solution
Dissolve 1g NaCl in 100ml of distilled water.
 Collection Of Saliva
Make a thin film of cotton and dip it into water. Drain off
the water of the cotton and spread it over the mouth of
funnel in such a way that it acts as a filter. Keep the
funnel
over a clean test tube.

Now chew a piece of rubber and pour the incoming

saliva into the funnel, filtered Siliva will collect in the
test tube. Take 1 ml of Saliva and add 19ml of water to
get 1:20 dilution of the enzyme.

THEORY
 Effect Of Temperature
At lower temperature, the enzyme is deactivated, and at
the higher temperature, the enzyme is denatured.
Therefore, more time will be taken by an enzyme to
digest the starch at lower and higher temperatures.
Optimum temperature for the enzymatic activity of
salary amylase ranges from 32°C to 37°C. At this
optimum temperature, enzyme is most active, and
hence takes less
time to digest the starch.
 Effect Of pH
The optimum pH for the enzymatic activity of Salivary
amylase ranges from 6 to 7. Above and below this
range, the reaction rate reduces as enzymes act
denatured. The enzyme Salivary amylase is most
active at 6.8pH.
 TEST FOR TEMPERATURE & PH

The effect of temperature and pH on the activity of Salivary

amylase on Starch can be Studied by using the Iodine test. If
we add Saliva and starch, the Salivary amylase present in
Saliva gradually acts on Starch and converts it into maltose.

At this point, no blue colour is formed. This is the end point

or achromic point.
 OBJECTIVE – 1
To study the action of salivary amylase starch.

Procedure: -
 Take 5ml of the starch solution in a test tube. Add 2ml
of saliva solution into it. label it as experimental tube.
Take another test tube containing 5ml Starch and 2ml
NaCl. Label it as control tube. Mix the solution well by
shaking the test tube carefully and stopwatch is to be
started at this point.
 After 1 minute take out two drops of the mixture
solution from each test tube with the help of a dropper
and transfer them into different test tubes containing
about 1ml of 1% iodine solution each. Note the colour
produced, if any.
 Repeat this test after everyone minute taking two drops
of the mixture solution and fresh one percent iodine
solution continue until the test shows blue colour.
Record the time and blue colour intensity.

Result: -
It takes 20 minutes for 1ml of diluted enzyme (1:20 Dilution)
to digest completely 5ml of 1% start solution to the
achromic point (end point).
At achromic point the experimental tube shows positive
benedict’s test indicating the presence of simple sugars and
absence of starch.

Observation Table: -
Time (min) Experimental Tube Control Tube
0 Blue Blue
2 Blue Blue
4 Blue Blue
6 Blue Blue
8 Blue Blue
10 Blue Blue
12 Blue Blue
14 Blue Blue
16 Blue Blue
18 Blue Blue
20 No change in colour Blue
 OBJECTIVE - 2
To study the effect of different temperatures on the
activity of salivary amylase on starch.

Procedure: -
 Make three series of test tubes having 1ml of iodine
solution in each. Keep them separately in three
stands.
 Make three experimental test tubes each having 5ml
of 1% starch and 1ml of 1% NaCl solution. Maintain
them at 37 ± 2°C and 70 ± 2°C in different water
baths, (To maintain ion temperature of 5°C, make use
of ice).
 Add 1ml of diluted enzyme in all the three
experimental tubes with the help of dropper take a
dropper from these test tubes and add to the test
tubes containing iodine. Note the time of adding as
zero minutes.
 After an interval of one minute again take a drop from
each tube and pour it to the iodine tubes and note
the change in colour of iodine keep on repeating the
experiment at an interval of every two minutes till the
colour of iodine does not change.
  Note the time taken for by different experimental
tubes till they do not give any colour with iodine.

Result: -
It takes less time to reach achromic point at 37°C as the
enzyme is maximum active at these temperatures more
time is taken to reach.

Observation Table: -

Time taken to reach

Temperature
the Achromatic Point
5 ± 2°C No result

37 ± 2°C 20 minutes

70 ± 2°C No result
 OBJECTIVE -3

To study the effect of different pH on the activity of

salivary amylase on starch.

Procedure: -
 Make 3 series of test tubes having 1ml of iodine
solution in each. Keep them separately in 3+ stands.
 To the three different test tubes. Add 5ml of 1% starch
solution, 1ml of 1% NaCl, and three tablets of known
pH - 5 6.8 and 8 into the test tube, respectively.
 Put these test tubes in a water bath at 37 degrees
Celsius, for 10 minutes. A beaker filled with water can
be used for this purpose during summer.
 To these test tubes, add 1 ml of diluted enzyme.
Immediately, with the help of separate droppers, take
a drop from each test tube and pour it to the test
tube having iodine solution to this way. You have
three series of iodine tubes, for pH- 5, 6.8 and 8. Note
the time of adding as Zero minutes. Keep these tubes
in water bath throughout the experiment.
 After interval of two minutes, again, take a drop from
each tube and pour it to the iodine. And note the
change of colour of iodine.
  Keep on repeating it after an interval of every two
minutes, till the colour of iodine doesn’t change. Note
the total time taken for these tubes till they do not
give any colour with iodine solution.

Result: -
 pH = 5 is acidic and pH = 8 is alkaline. Therefore,
salivary amylase doesn’t act in these tubes.
Whereas, the enzyme acted in the tube with pH =
6.8 and digested the starch.

Observation Table: -

pH Time taken to reach

the Achromic Point

5 No Result

6.8 20 minutes

8 No result
 Precautions
 Filter the saliva through a wet cotton film and not
through a filter paper.
 All the weighing and measuring should be done
accurately.
 Maintain uniform temperature of the water for bath,
throughout the experiment.
 While measuring saliva, there should be no air bubbles.
 All glassware wed must be thoroughly cleaned and
dried.

Bibliography: -
 Wikipedia