Final Lab Project
Apples/Enzymatic Browning
Materials:
-Apple Slices
-test tube with 0.1% Ascorbic
-test tube with 0.1% Citric acid test tube
-test tube with 0.1% Acetic acid test tube
-test tube with 1.0% Acetic acid test tube
-Beaker with water
-tongs
-experiment mat
This experiment will monitor the amount of enzymatic browning of apple slices. In apples there is an enzyme called phenolase. When an apple is touched by oxygen, the phenolase catalyses the formation of brown pigments. If we treat the apples with acids such as ascorbic, citric or acetic acids this will reduce the level of browning. When fruits and vegetables are cut the enzymes are released in the presence of oxygen and produces brown pigments known as melanins.
First we will label a paper towel "Control" and place an untreated apple slice on the control towel. Using the tongs, dip each apple slice into the solutions (.1% ascorbic, .1% citric, .1% acetic, 1.0% acetic) and lay each slice tested with the different solutions onto a towel labeled with that solution. Take one slice and soak it in the beaker with water for 30 seconds and again place it on a paper labeled "Water". Begin to observe the apple slices every ten minutes for 1 hour.
|
Time
|
Control
|
.1% Ascorbic
|
.1% Citric
|
.1% Acetic
|
1.0% Acetic
|
Water
|
|
10min
|
1
|
1
|
1
|
1
|
1
|
1
|
|
20min
|
2
|
2
|
1
|
1
|
1
|
1
|
|
30min
|
3
|
2
|
2
|
1
|
1
|
1
|
|
40min
|
3
|
3
|
2
|
2
|
1
|
1
|
|
50min
|
3
|
3
|
2
|
2
|
1
|
1
|
|
60min
|
4
|
4
|
2
|
2
|
2
|
1
|
4 dark brown 3 browning 2 slight browning 1 no brown
My conclusion is that the browning is caused by the change of more weak acidic compounds. In order for the browning process to occur you need oxygen to be present. Ascorbic acid stops the oxygen from reacting. Citric and acetic acid both lower the levels of pH which minimizes the browning process. With that being said, because both citric and ascorbic acid are present in the apple (they lower the pH) causes a reduction in the activity of the enzyme.