FOOD TESTS A Collection Of Experiments

I'm Going To Share Some Experiments You Can Try To Carryout To Test Foods For Starch, Reducing sugar, Proteins, Fats, and Vitamin C And What Reagents to Use to test For this.

Food Test
You will have seen that the packaging of foods always lists the contents, for example, the amount of carbohydrates, protein, fat, and so on. Simple tests, described as tood tests, can be carried out on foods to find out what nutrients they contain. Each type of nutrient has its own food test. You will be required to know and understand the practical procedures for testing foods, to identify the nutrients that are contained within them

Whenever a food test is being carried out, certain procedures need to be tollowed:
• A standard test should alvways be done first. For example, if foods are being tested for simple sugar, a known simple sugar should be tested. The results of this test can be compared with results from other foods.
• Foods should be kept completely separate from each other, this means using clean containers for each kind of food.
• The same amount of reagent should be used for each test.

EXPERIMENT 1
Practical investigation: Using iodine to test food for starch (iodine test)
This is a practical activity may take you about 20 minutes.
You will need:
• a small amount ot bread, sugar and uncooked potato
• a small plate or saucer
• iodine solution, which you can obtain from your pharmacist
• if available, a dropper pipette or syringe.
Method:
1. In your notebook, draw a results chart with the following headings:
• Food substances
• Observations
• Conclusions
2. Put a small piece of the potato on the plate or saucer.
3. Add a drop or two of iodine solution.
4. Record any change of colour in your result chart.
5. Repeat with the other samples of food using a clean plate each time

*Note it, Dropper pipettes and syringes are often used for giving medicine to young children and can usually be obtained from pharmacists/ chemical shops; you could use a small spoon instead. lodine solution is brown, but it turns black if there is starch in the food*

EXPERIMENT 2
Practical investigation: Using Benedict's solution to test food for a reducing sugar (Benedict's test)
This test uses a chemical called Benedict's solution. Benedict's solution Contains copper salts and therefore has a blue colour.
Method:
1. Cut or crush a piece of food into very small pieces and put it in a test-tube.
2. Add some water (approximately 2 cm3) and shake the tube to help the food dissolve and make a solution.
3. Add the same volume of Benedict's solution.
4. Heat the solution very carefully.
• If a large amount of reducing sugar is present in the food, the Benedict's solution will turn an orange-red colour. If only a small amount ot reducing sugar is present in the food, the Benedict's solution will turn a greenish-yellow colour. This test works because the simple sugar reduces the blue copper salts in the Benedict's solution to a red compound. Sugars that do this are called reducing sugars. All simple sugars are reducing sugars, as are some complex sugars.

*Note that, The food test described here is used to identity the presence of reducing Sugars. Read about this test and learn the techniques, the name of the reagents used and the procedure to follow*

EXPERIMENT 3
Practical investigation: Using Biuret solution to test food for proteins (Biuret test)
This test for proteins uses two chemicals
• potassium hydroxide solution
• copper sulphate solution
Method:
1. Put a small amount of food into a test-tube and add a little water.
2. Add some potassium hydroxide solution.
3. Then add two drops of copper sulphate solution.
4. When the tube is shaken gently, a purple colour appears if protein is present.
If the colour remains blue, there is no protein present.

*Learn the test for proteins, and what results to expect if a food contains protein, or if it does not*

EXPERIMENT 4
Practical investigation: Using ethanol solution to test food for fats (emulsion test)
Fats will not dissolve in water, but they will dissolve in ethanol.
Method:
1. Put a small amount of food into a very clean, dry container. Add ethanol. Shake
it thoroughly.
2. Put water in another container.
3. Pour some of the liquid from the first container into the water.
4. If a solution of fat in ethanol is added to water, the fat forms tiny globules that float in the water. This is called an emulsion. The globules of fat make the water look milky.

*lf you are testing any solid food, you will need to chop or grind the food. Learn how to do the test for fats, and what results to expect it food contains fat, or if it does not. Ethanol is a very pure form of alcohol take care not to let anyone taste the ethanol. It is very dangerous*

EXPERIMENT 5
Practical investigation: Using DCPIP solution to test for ascorbic acid (vitamin C)
This test for vitamin C (ascorbic acid) uses a blue reagent, DCPIP, which is made colourless by vitamin C. Fruit juices that are acid turn the DCPIP from blue to red, but it is the point at which the dye becomes colourless that matters. Some fruit juices, like orange, are coloured, so in these cases the end point of the experiment occurs when the original colour can be seen once more.
Method:
1. Put a standard volume of the same concentration DCPIP in a test-tube.
2. Place one canned fruit juice sample in a syringe/dropper.
3. Add the fruit juice drop by drop to the DCPIP.
4. Shake the DCPIP after each drop of fruit juice is added.
5. When the DCPIP goes clear, record the number of drops of fruit juice you added.
6. Repeat the test with other fruit juice samples and make notes.
7. The fewer the drops needed to remove the blue colour from the solution, the more concentrated the vitamin C in the food sample.

Easy Figure Summary Of The Tests Used To Identify Nutrients In Food

The End See You In The Next Post. Posted by Mr DeHaan Ahil.