Effects of Acids on Fruit Oxidation
Acidity’s effects on Fruit Browning
Aim: To test whether the acidity of the surface area of an apple has an effect on the rate of enzymatic browning over 70 minutes.
Hypothesis: the more acidic the surface area the longer it takes for the fruit to oxidise.
Variables: Independent: acidity of surface area of the apple Dependent: the progression of melanin (brown pigment) after 70 minutes
Controlled/fixed: time of day, knife used to cut fruit, portion of fruit, environment (room temperature, humidity etc.)
Materials:
2 apples
A stopwatch
A camera
7 cups
7 plates
Paper and pen (for labels)
300mL of vinegar
300mL of orange juice
300mL of lemon juice
300mL of milk
300mL of water
300mL of methylated spirits
300mL of baking soda solution
1 serrated knife
Method:
1. Gather all materials and determine the pH of the 7 substances used.
2. Make the baking soda solution by dissolving the powder into water at a ratio of 1:3.
3. Pour each substance into a cup; roughly 150mL of each, label each cup with the substance that is in it.
4. Place a plate directly in front of each cup like in the apparatus above.
5. Cut 1 apple into 8 segments and place each segment onto a plate.
6. Using your hands slowly dip the apple into each substance and place it on the plate in front of the cup with that substance in it. (Make sure your hands are cleaned after every apple)
7. Start the timer and every ten minutes rate the progression of discolouration on each apple on the scale listed below. Take photos.
8. Repeat experiment (steps 1-7) one more time using the remaining apple.
9. Record the results in the table.
SCALE
0 - no browning present
1- Brown dots
2 -Brown patches
3 - Half-covered light brown
4 - Completely light brown
5 - Completely dark brown
Results: pH of Substance
Time (mins)
0
10
20
30
40
50
60
70
1
2
Av.
1
2
Av.
1
2
Av.
1
2
Av.
1
2
Av.
1
2
Av.
1
2
Av.
1
Aim: To test whether the acidity of the surface area of an apple has an effect on the rate of enzymatic browning over 70 minutes.
Hypothesis: the more acidic the surface area the longer it takes for the fruit to oxidise.
Variables: Independent: acidity of surface area of the apple Dependent: the progression of melanin (brown pigment) after 70 minutes
Controlled/fixed: time of day, knife used to cut fruit, portion of fruit, environment (room temperature, humidity etc.)
Materials:
2 apples
A stopwatch
A camera
7 cups
7 plates
Paper and pen (for labels)
300mL of vinegar
300mL of orange juice
300mL of lemon juice
300mL of milk
300mL of water
300mL of methylated spirits
300mL of baking soda solution
1 serrated knife
Method:
1. Gather all materials and determine the pH of the 7 substances used.
2. Make the baking soda solution by dissolving the powder into water at a ratio of 1:3.
3. Pour each substance into a cup; roughly 150mL of each, label each cup with the substance that is in it.
4. Place a plate directly in front of each cup like in the apparatus above.
5. Cut 1 apple into 8 segments and place each segment onto a plate.
6. Using your hands slowly dip the apple into each substance and place it on the plate in front of the cup with that substance in it. (Make sure your hands are cleaned after every apple)
7. Start the timer and every ten minutes rate the progression of discolouration on each apple on the scale listed below. Take photos.
8. Repeat experiment (steps 1-7) one more time using the remaining apple.
9. Record the results in the table.
SCALE
0 - no browning present
1- Brown dots
2 -Brown patches
3 - Half-covered light brown
4 - Completely light brown
5 - Completely dark brown
Results: pH of Substance
Time (mins)
0
10
20
30
40
50
60
70
1
2
Av.
1
2
Av.
1
2
Av.
1
2
Av.
1
2
Av.
1
2
Av.
1
2
Av.
1