Biology Oreo

Detection of food substances by food

tests

(02)Chan Tracey Wing Tung (12)Lee Hei Tung(15)Luk Ka Wing(22)Yeung Ka Tak F.3A

Objective

• To test for the presence of glucose, reducing sugar, starch, fats, proteins and vitamin C by different food tests

Background information

Food substance Food testGlucose Using Clinistix paperReducing sugars Benedict’s test

Starch Iodine test

Fats Grease spot test

Proteins Using Albustix paperVitamin C Using DCPIP

solution

Test for food substance in solid food substance ( Oreo

)1.Cut the food sample

into small pieces.

2.Put the small pieces into a mortar and grind with a small quantity of cool distilled water using the pestle.

A.Test for glucose using Clinistix paper1.Transfer a drop

of glucose solution to the well of a spot plate.

2. Dip the test end of a Clinistix paper into the sample and observe any colour change. Use distilled water as a control .

Oreo solution

Water

Water

Oreo solution

Result

SampleTest end of Clinistix paper

Original colour

Final colour

Glucose solution Pink Purple

Distilled Pink Pink

B. Test for reducing sugars using Bendict’s test

1.Mix equal volumes (e.g.1cm³)of glucose solution and Benedict’s solution in s test tube.

2.Put the test tube into a boiling water bath. Boil the mixture for 5 mins and observe any in the mixture.

3.Stand the test tube in a test tube rack for 15 mins and observe any change in the mixture again. Use distilled water as a control.

Bendict solution

Oreo solution

After Water Bath:

Bendict solution+Oreo solution

Results

Sample Mixture of Benedict’s solution and sample

Original colour

Final change

Glucose solution

Light blue Brick red precipitate

Distilled Light blue Light blue

C. Test for starch using iodine test

1.Transfer a drop of starch solution to the well of a spot plate.

2.Add a drop of iodine solution to the sample and observe any colour change. Use distilled water as a control.

Oreo solution+ iodine

Water + iodine

Results

SampleIodine solution

Original colour

Final colour

Starch solution

Brown Blue-black

Distilled water

Brown Brown

D. Test for fats using grease spot test

1.Transfer a drop of cooking oil to a filter paper and let it dry in the air for 5 mins

2.Hold up the filter paper to the light and observe any translucent spot

3.Immerse the filter paper into a original solvent (e.g. ether, acetone).

4.Examine the filter paper against light again. Note any change in the filter paper. Use egg white solution and distilled water as controls.

Oreo solutionWater

Results

Sample

Presence of translucent spot after drying?

Before immersing

into organic solvent

After immersing

into organic solvent

Cooking oil Yes No

Egg white solution

Yes Yes

Distilled water

No Not applicable

E.Test for proteins using Albustix paper

1.Transfer a drop of egg white solution to the well of a spot plate.

Oreo solution

Water

Oreo solution

water

2.Dip the test end of an Albustix paper into the sample and observe any colour change. Use distilled water as a control.

Oreo solution

Water

Result

Sample Test and of Albustix paper

Original colour

Final colour

Egg white solution

Yellow Blue-green

Distilled water

Yellow Yellow

F.Test for vitamin C using DCPIP solution

1.Put 1 cm3 of DCPIP solution in a test tube.

2.Add in vitamin C solution drop by drop. Stop when there is any persistent colour change.

DCPIP solution

Add in Oreo solution

3.Boil a test tube of 5cm3 of vitamin C solution in a boiling water bath for 5 mins. Allow the test to cool in a breaker of cold water.

4.Use the boiled vitamin C solution and distilled water as controls.

Control

(Add Water)

Oreo

solution+DCPIP solution

Results

Sample DCPIP solution

Original colour

Final colour

Vitamin C solution

Blue colourless

Boiled vitamin C solution

Blue Blue

Distilled water

Blue Blue

Apparatus & Materials used

Apparatus & Materials used

• Test tube• Test tube holder• Filter paper• Filter funnel• Beaker• Mortar• Grind• Spot plate• Dropper• Measuring cylinder• Water boiling bath

• Oreo biscuits• Distilled Water• Clinistix paper• Bendict’s solution• Iodine solution• Albustix paper• DCPIP solution

Conclusion

• In our tests, Oreo has the reaction on:• Glucose (Clinistix paper) +ve• Reducing sugar (Benedict’s test) +ve• Starch (Iodine test) +ve• Fat (Grease spot test) -ve• Protein (Albustix paper) +ve

• Vitamim C(DCPIP solution) +ve

Experimental Errors & Improvement

• Oreo should have positive result on fats. However, in our test, we have negative result since there is little amount of fat in Oreo.

• We need to be more careful in cleaning all the apparatus before we use them again. Eg.There is also colour change in our control (water).