Chemistry Investigatory Project

E nzymatic hydrolysis of starch

Investigatory Project Report

Name:
Class/Sec:
Board Roll No:

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 INDEX
Serial no. Contents Page no.
1. Acknowledgement 4

2. Aim 5

3. Objectives 6

4. Introduction 7

5. Problem questions 8
6. Materials Required
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7. Procedure 10

8. Observation 14

9. Conclusion 15
10. Limitations 16

11. Bibliography 16

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 ACKNOWLEDGEMENT
I would like to take this opportunity to thank my chemistry
teacher – Mrs. Indu Narang, for encouraging and guiding me in
my project and for providing valuable suggestions. I am also
grateful to our lab assistant, Mrs. Shashi Singh who has helped
me with the setup for the project and gave practical insight.

I would like to extend my gratitude to the Principal Dr. H.S.

Vashistha and the Senior Secondary Chemistry Department of
my school, Delhi Public School, Nerul for providing me with
this opportunity to conduct this insightful project.
Also, a big thank you to my fellow group members for their
contributions in this project.
I would also like to thank my parents for their generous support
throughout my schooling.

I believe that this small project will make a significant impact

by inspiring someone else to continue my research

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 AIM
“ To study the digestion of Starch by salivary
amylase and effect of temperature and pH on
it. ”

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 Objective of the Project Report
The main objective of this chemistry project report is
“To study the digestion of starch by salivary amylase
and effect of temperature and pH on it” .

1. To study the digestion of starch by saliva.

2. To study the effect of temperature on the digestion of
starch by saliva.
3. To study the effect of pH on the salivary digestion of
starch.

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 Introduction
Every health book insists on the chewing of food. The act of
chewing stimulates the excretion of saliva. Saliva mixes up
with the food and helps its digestion. That is, the enzyme
ptyalin or amylase present in human saliva hydrolyzes the
big molecules of food into many molecules.

For example, starch into mono-saccnaricies maltose and

glucose; proteins into amino acids and fats into fatty acids
and glycerol.
Thus saliva not only helps in digestion of food but also
convert into energy generating substances. Further, enzyme
and their activity are very sensitive to temperature and pH.
Even a slight variation in these two factors, can disturb the
action of enzymes. In other words, digestion of food by
salivary amylase is also effected by temperature and pH and
can be verified experimentally.
For example, hydrolysis of starch can be verified by testing it
with iodine solution. Starch forms blue coloured complex
with iodine. If no starch is present in a system it will not give
blue colour with iodine.

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 Problem Questions
Q.1. What is the role of iodine in the starch digestion experiment,
and how can you interpret the results based on the color changes
observed?
Ans.1. Iodine solution is used as an indicator to test for the presence of
starch. When iodine is added to a solution containing starch, it forms a
blue-black complex, indicating the presence of starch. During the
starch digestion experiment, observing the color change helps
determine the progress of starch hydrolysis by salivary amylase. If the
solution remains blue-black, it indicates that starch is still present and
has not been fully digested. As the enzyme breaks down the starch into
maltose and glucose, the blue-black color fades. The disappearance of
the blue-black color indicates the complete digestion of starch,
confirming the enzyme's activity.
Q.2. Why is iodine solution used in the saliva experiment to test for
starch?
Ans.2. Iodine solution is used in the saliva experiment to test for starch
because iodine reacts with starch to produce a blue-black color. This
color change indicates the presence of starch in the solution, allowing
us to observe the digestion of starch by salivary amylase. When the
starch is broken down into simpler sugars by the enzyme, the blue-
black color fades, indicating the completion of the reaction.
Q.3. How does temperature affect the activity of salivary amylase?
Ans.3. Temperature affects the activity of salivary amylase
significantly. At optimal temperature (around 37°C, which is close to
body temperature), the enzyme works efficiently to break down starch.
However, at lower temperatures, the enzyme activity slows down, and
at higher temperatures (e.g., boiling water), the enzyme can become
denatured and lose its functionality, thus inhibiting the digestion of
starch.

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 Apparatus Required
The requirements for experiment of chemistry project report
Are as follow:
1. Test tubes
2. Test tube stand
3. One dropper
4. Beaker
5. Stop watch
6. Starch
7. Iodine solution
8. Thermometer
9. Dilute HCl solution
10. Dilute NaOH solution

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 Experiment 1
Aim:- To study the digestion of starch by saliva

Procedure for Chemistry Experiment 1 is:

1. Collection of Saliva:- Rinse mouth thoroughly with cold

water and ensure that it does not contain any food
particles. Now take about 250ml of lukewarm water in
the mouth and keep for about three minutes so that saliva
mixes up well with it. Spit this into a beaker. Filter, if
there is any suspended impurity clear filtrate is saliva
solution and contains enzyme ptylin.
2. Preparation of starch solution:- Take about 0.5g of starch
in 100ml beaker and add enough water to make a paste.
Dilute the paste by adding 50ml water and boil for about
5 minutes.
3. Digestion of starch:-
a. Take 5ml of the starch solution in a test tube. Add
2ml of saliva solution into it. Mix the solution well
by shaking the tube carefully and start a step watch.
b. After one minute, take out two drops of the mixture
solution from the test tube with the help of dropper
and transfer it into another test tube containing
about 1ml of 1% iodine solution. Note the colour
produced, if any.

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 c.
d. Repeat this test after every one minute taking two
drops of the mixture solution and fresh 1% iodine
solution continue until the test shows no blue colour.
e. Record the time and blue colour intensity.

Observation
Time Passed after 1 2 3 4
Mixing minute minute minute minute
Colour Intensity Deep Blue Light No Blue
Blue Blue

Absence of blue colour on addition to iodine solution means

absence of starch in the mixture solution. That is whole of
the starch has got digested or hydrolysed.

Conclusion
Starch gets hydrolysed by salivary amylase

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 Experiment 2
Aim:- To study the effect of temperature on the digestion of
starch by saliva.

Procedure for Chemistry Experiment 2 is:

1. Take three test tubes and label these 1,2, and 3.

2. Take 5ml of the starch solution, 2ml of the saliva solution
and 5ml of water in each test tube. And shake the test
tubes carefully.
3. Place test tube number 1 in water at room temperature,
test tube number 2 in a beaker containing water at 50°C
and test tube number 3 in boiling water.
4. After 5 minutes, observe the colour change on mixing
two drops of the mixture of every tube with one ml of 1%
iodine solution. Note the intensity of blue coloured form.

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 Observation
Time passed after Intensity of blue colour
mixing saliva Test tube 1 at
s olution with starch room Test tube 2 at 50°𝑪 Test tube 3 in
solution (in min) temperature boiling water
5 Light blue Blue Deep blue
6 No blue colour Light blue Blue
7 - Faint blue Blue
8 - No blue colour Blue
9 - - Blue
10 - - Blue

Conclusion
Temperature affects the digestion of starch by
saliva.

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 Experiment 3
Aim:- To study the effect of pH on the salivary digestion of
starch.
Procedure for Chemistry Experiment 1 is:
1. Take three test tubes and label these 1,2, and 3.
2. Add 5ml of the starch solution, 2ml of the saliva solution
in each test tube.
3. Now as 2ml of water in test tube number 1 2ml of Dilute
HCl in test tube number 2 and 2ml of Dilute NaOH
solution in test tube number 3 and shake carefully.
4. Keep the three test tubes in water at room temperature
for about 10 minutes.
5. Add 2 drops of the solution of each test tube with 1%
iodine solution and observe the colour change.

Observation
Colour produced (in test
Test tube Solution taken tube) with 1% iodine
solution
1 Starch + saliva + water No blue colour
2 Starch + saliva +dil. HCl Blue colour
3 Starch + saliva + dil. NaOH Blue colour

Conclusion
Hydrolysis of starch by the enzyme does not take place in
the acidic or alkaline medium.

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 Limitations
Limitation 1: Variability in Saliva Composition
Explanation: Saliva composition varies between individuals and times
of day, affecting amylase concentration and leading to inconsistent
results.
Limitation 2: Difficulty in Maintaining Constant Experimental
Conditions
Explanation: Maintaining constant temperature and pH is challenging,
and fluctuations can influence enzyme activity and affect accuracy.
Limitation 3: Sensitivity to External Contaminants
Explanation: The experiment is sensitive to contaminants in saliva,
starch solution, or equipment, which can interfere with results.
Limitation 4: Subjectivity in Observing Color Changes
Explanation: Interpretation of color changes in the iodine test is
subjective, leading to variations. Using objective measurement tools
could help but may not always be available.

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 Bibliography
1. Libretexts-chem
2. http://www.google.com/
3. http://en.wikipedia.org
4. www.icbse.com
5. Comprehensive Chemistry
6. Chemistry NCERT Class XIIt

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