Chemistry
Investigatory
Project
Browning of
Apples
By: - Akash Garhwal
Class: - XII Science
School: - Kendriya Vidyalaya
Sikar
Kendriya Vidyalaya Sikar
Exam roll no:This is to certify that Akash Garhwal, a
student of Class XII Sci. has successfully
completed the project guided by Mr. Ajay
Kumar (subject teacher) during the
academic year 2017-18 in practical
fulfilment
of
Chemistry
practical
examination conducted by AISSCE .
Signature of Examiner:->
Sign. Of Chemistry Teacher :->
AIM:To study the factor those are
affecting apple slices turning
brown and the best way to
preserve the apple slices.
ACKNOWLEDGEMT: In the accomplishment of this project
successfully. Many people have best owned
upon me their blessings and the heart
pleaged support, their time I am utilizing to
thank all the people who have been
concerned with the project.
Primarily I would thank god for being able to
complete this project with success. Then I
would like to my principal
Mr. Prahalad
Singh and Chemistry teacher Mr. Ajay
Kumar , whose valuable guidance has been
the once that helped me this project and
makes it full proof success his suggestions
and his instructions has served as the major
contributor toward the completion of this
project
Then I would like to thank my parents and
friends who have helped me with their
valuable suggestions and guidance has been
helpful in various phase of the completion of
the project.
CONTENT:1) Theory
2) Material required
3) Procedure
4) Result
5) Conclusion
THEORY:Apples contain an enzyme called “polyphenol
oxidase“(phenolase). In the presence of oxygen from air, this
enzyme catalysis the formation of brown pigment called
“melanins”.
Treatment of the apple slices with ascorbic acid, citric acid, or
acetic acid will reduce the level of browning. The reduction in
browning is dependent on the type of substance and its
concentration. Soaking in water will temporarily reduce the level
of browning by restricting the amount of oxygen in contact with
apple slices.
When fruit or vegetable is peeled or cut, enzyme contained in the
plant cell are released. In presence of air, the enzyme phenolase
catalyses one step in the biochemical conversion of plant
phenolic compound to form brown pigment called melanins. This
reaction, called enzymatic browning, occurs readily at warm
temperature when pH is between 5.0 and 7.0. The presence of
Iron or Copper can increase the rate of reaction. This can easily
be observed when fruit is cut with a rusty knife or mixed in a
copper bowl.
Bruising or other injury to the plant tissue disrupts the
arrangement of chemicals within the cells and allows these
chemicals to make contact with oxygen. This may lead to
browning of uncooked fruits. Enzymatic browning can be
significant problem, limiting the shelf life of many fruits and
vegetables which have had little heat applied during processing.
However, enzymatic browning is not always a defect. The
browning reaction contributes to the desirable colour and flavour
of raisins, prunes, coffee, tea and cocoa.
Material Required:-
Apples
pH paper
Tongs
Glasses
Pens
Knife
Plastic Gloves
A timer
Lemon juice
Orange juice
Soda
Mineral water
Baking soda
- Water
Procedure:The method I used was to
1.
First
get each substance and then to take the
pH stripes and test the pH of each liquid,
then cut apples into slices and line up
slices of apple on table
2.
Plac
e an untreated apple slice on a paper
towel. Label the towel “Control”.
3.
Usin
g tongs, dip an apple slice into lemon
juice for 30 seconds, place it on towel,
and label with the same name of solution.
4.
Rins
e the tongs and repeat the same
procedure for the other five solutions.
5.
Soa
k one slice in water for 30 second. Place it
on a towel and label the towel “Water
Soak”.
6.
The
n to set the timer, then to record how long
it takes for each apple slice with different
substance on it to turn dark brown.
7.
Note
the time and temperature in your data
table. Compare your result with those
obtained.
OBSERVATI
ON:-
What Substance Prevent
Apples from Browning ?
30
25
20
15
Time(Mins)
10
5
0
Lemon juice
Orange juice
Tomato juice
Milk
Black coffee
Water
RESULT:My results were that the lemon juice is the best
preservative to put on apple slices and that
baking soda is worst. The order of the
preservatives from best to worst goes from
lemon juice, to soda, to mineral water, to water,
to an apple slice with nothing on it (control), to
orange juice and ending with baking soda.
My results for the second experiment were that
the best temperature to put apple slice at is a
warm such as 100˚ Fahrenheit, then at room
temperature of39˚ Fahrenheit, and ending with
the worst temperature to put apple slices at when
wanting to preserve them which is a freezing
temperature such as 32˚ Fahrenheit.
CONCLUSION:-
I come to the conclusion that lemon juice is
the best substance to put on apple slices
when wanting to preserve them because it is
high in citric acid. It is also has Vitamin A, C
and E in it. These are good because it lowers
the pH level of the apple causing it to turn
brown slower. It is best to put apple slices at
a hot temperature because if you put it at a
cold, the ice breaks down the cell wall of the
apple and introduces the enzyme called
“polyphenol oxidase” to air which turns the
apple brown.
Fig.:- Browning of apple with different
substance