Form 4 Food Tests and Enzymes Ms.E.Fenech Imbroll

Practical 1

Title: Finding the optimum pH of the enzyme that causes browning in apples

Aim: To find the pH at which the enzyme which turns apples brown work best

Apparatus and Materials:

5 pieces of apple

5 plastic cups/beakers

Hydrochloric Acid

Sodium Hydroxide

Water

Method:

1. The cups were labeled (HCl, NaOH, Water)

2. A slice of apple was added to each cup.

3. 1/4 cup of a substance was poured over the apple in its labeled cup. The substance was swirled

around the cup to make sure the apple slice is completely coated.

4. The appearance of the apple slices was noted immediately after treatment.

5. The apple slices were set aside for a day.

6. After 2 days, apple slices were observed and observations were recorded in a table.

7. A photograph of the apple slices was taken

8. Apples, cups and contents were disposed of after the experiment.

Diagram: Insert diagram here

Predictions:

What do you predict should happen to the apples in

i) Acidic solution?

ii) Netural solution?

iii) Alkaline solution?

Errors and Precautions:

What precautions did you need to take whilst handling the chemicals?

Where did you throw the chemicals?

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Form 4 Food Tests and Enzymes Ms.E.Fenech Imbroll

Where the apples suitable to be eaten?

Results:

Apple Treatment Apple Appearance after 2 days Photo

HCl (acidic)

Water (neutral)

NaOH (alkaline)

Discussion

What is the name of the enzyme which effects the browning of apples? Tyrosinase, find some

information about it and write a short paragraph.

Do all of your apple slices look the same? Are some different from others?

Were your predictions close to what happened in reality?

HCl is an acid, Water is neutral and NaOH is alkaline. From the results obtained, can you

conclude whether acids, neutral or alkaline were able to decrease and increase the activity of

this enzyme?

Which of the three chemicals effected most the rate of browning of apples?

Which of the three chemicals effected least the rate of browning of apples?

Relate this result to the optimum pH of this particular enzyme

Conclusion:

At what pH does the enzyme tyrosiase work best?

What happens to this enzyme in acidic conditions?

How can this information be used in the common kitchen.

Any possible improvements to this experiment? (example, use a range of pH? Can you say that pH is the

only factor effecting the enzyme from this experiment?)

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Form 4 Food Tests and Enzymes Ms.E.Fenech Imbroll

Practical 2

Title: Investigating the effect of surface area of the enzyme catalase

Aim: To investigate the effect of surface area of the enzyme catalase

Apparatus: potato, ruler, knife, tile, boiling tubes, hydrogen peroxide

Diagram:

Method:

1. Peel a potato2. Put the potato on a tile and cut 2 equal pieces of potatoes using a knife3. Cut one of the potato slices into small pieces.4. Put 2 boiling tubes in a rack and half fill them with equal amounts of hydrogen peroxide5. Put the potatoes in the boiling tubes6. Observe what happens

Predictions:

What do you predict should happen in both testtubes?

In which test tube do you predict the reaction should be the fastest?

Precautions:

Take care when cutting the potatoes What precautions did you take on handling the hydrogen peroxide? Why is this so? Why was it made sure that the potatoes were equal in size? Why were equal amounts of hydrogen peroxide in the boiling tubes?

Results:

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Form 4 Food Tests and Enzymes Ms.E.Fenech Imbroll

What happens when you put the potatoes in the hydrogen peroxide? Did you observe any changes in the two set ups?

Conclusion:

What reaction is taking place in the boiling tube? What is the froth? What factor caused a change in the amount of froth produced?

Practical 3:

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Form 4 Food Tests and Enzymes Ms.E.Fenech Imbroll

Title: Investigating the effect of temperature of the enzyme catalase

Aim: To investigate the effect of temperature of the enzyme catalase

Apparatus: potato, knife, tile, boiling tubes, beakers, hydrogen peroxide, Bunsen burner, tripod, gauze

Diagram:

Cold water Warm water Hot water

Cold Water Warm Water Hot Water

Predictions:

What do you predict should happen to the rate of reaction. In which test tube do you believe the rate of reaction should be the fastest?

Method:

1. Peel a potato2. Put the potato on a tile and cut 3 equal pieces of potatoes using a knife3. Put 3 boiling tubes in a rack and half fill them with equal amounts of hydrogen peroxide4. Put the potatoes in the boiling tubes5. Place one boiling tube in a cold water, one at room temperature and one in boiling water6. Observe what happens

Errors and Precautions:

What precautions did you take on handling hydrogen peroxide? Why were these needed? What precautions on handling the boiling water? Where there any errors in your setup? How could have these been avoided?

Results:

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Form 4 Food Tests and Enzymes Ms.E.Fenech Imbroll

Which set up produced the most froth? Which set up produced the least froth?

Conclusion:

Give a clear biological explanation why there was a difference between the amount of froth produced.

Sketch a graph to show the best temperature in which catalase works. What are enzymes? Mention some of their uses.

Practical 4:

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Form 4 Food Tests and Enzymes Ms.E.Fenech Imbroll

Title: Food Tests

Aim: To predict and test the content of some food tests

Apparatus & Materials:

Food samples

Test tubes

Test tube rack

Pipettes

Bunsen Burner

Benedict’s Solution

Iodine Solution

Ethanol

Sodium Hydroxide

Copper sulphate solution

Predictions

Food Starch Test Glucose Test Protein Test Fat Test

Soft Drink

Bread

Ham

Cooking Oil

Egg White

Krisps

Milk

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Form 4 Food Tests and Enzymes Ms.E.Fenech Imbroll

Method:

1. What do you predict each food test should contain?

2. Mash each food sample in a mortar and pestle. Add water for hard food samples.

3. Carry the following tests for each food item.

A. Test for Glucose (Reducing Sugars)1. Put a little food sample into 5 different test tubes2. Add a few drops of Benedict’s solution to each test tube3. Carefully, heat the test tubes in a water bath 4. Observe what happens

ColourNo Change(Blue)GreenYellowOrangeBrick-red

INTERPRETATIONNo non-reducing sugars presentTrace amounts of non-reducing sugars presentLow amounts of reducing sugars presentModerate amounts of reducing sugars presentLarge amounts of non-reducing sugars present

B. Test for Starch1. Put a little food sample into 5 different test tubes2. Add a few drops of Iodine solution to each test tube3. Observe what happens

Blue black solutionStarch is present.....

Brown (no change) No starch present

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Form 4 Food Tests and Enzymes Ms.E.Fenech Imbroll

C. Test for Protein1. Put a little food sample into 5 different test tubes2. Add 2cm3 of sodium hydroxide solution3. Add 2cm3 of copper sulphate solution4. Observe what happens

Buiret solution is a blue liquid that changes to purple when proteins are present and to pink in the presence of short chains of polypeptides

D. Test for Fat

1. Put a little food sample into 5 different test tubes

2. Add 2cm3 of Ethanol solution and shake3. Add 2cm3 of water and shake 4. Observe what happens

A white (milk-like) emulsion indicates the presence of fats or oils.

(Instead, you can do grease spot test, where Grease spot test/Brown paper testAs we all know from experience, lipids leave translucent spots (grease spots) on unglazed brown paper bags. Use four squares onto their brown paper bag, then use a cotton swab to put samples of three lipids of their choice and water as a control into the squares. Wipe off excess oil/fat and let sit for few minutes to dry. Once dry, the fats will left a translucent spot behind. This can best be seen when you hold the paper up to a light source).

Results:

Food Starch Test Glucose Test Protein Test Fat Test

Colour Present? Colour Present? Colour Present? Colour Present?

Soft Drink

Bread

Ham

Cooking Oil

Egg White

Krips

Milk

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Form 4 Food Tests and Enzymes Ms.E.Fenech Imbroll

Discussion and Conclusion:

1. Which food items contained starch? Why?

2. Which food items contained glucose (reducing sugar)? Why?

3. Which food items contained protein? Why?

4. Which food items contained fats? Why?

5. Which food should people who are on a diet avoid?

6. Which food do you recommend for athletes?

7. Which food would you recommend for children?

8. How would you link this experiment with the importance of a balanced diet?

http://www.bbc.co.uk/schools/ks3bitesize/science/organisms_behaviour_health/

food_detective/activity.shtml

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Photos

Practical 1 Photos

Apple in Acidic Solution Apple in Neutral Solution Apple in Alkaline Solution

Practical 2 Photos

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Form 4 Food Tests and Enzymes Ms.E.Fenech Imbroll

Potato with High SA Potato with Low SA

Practical 3 Photos

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Form 4 Food Tests and Enzymes Ms.E.Fenech Imbroll

Test Tube at 100oC Test tube at 30oC Test tube at 0oC

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Form 4 Food Tests and Enzymes Ms.E.Fenech Imbroll

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