-
Experiment OB3A, To test a variety of foods for the pressence of startch.
-
The Experiment involves the use of chemicals. So wear safety goggles and gloves during the experiment.
-
Today the chemical we will be using is Iodine solution. Which is Redish / Brown colour.
-
And it will stain blue / black when startch is present.
-
The foods we will be testing are Potatoe, Flour and Milk.
-
The experiment simply involves adding a few drops of Iodine. To each food sample.
-
When a few drops are added to the potatoe. It will stain Blue / Black in colour.
-
Which indicates startch is present.
-
When we add the chemical to flour. Again it will stain Blue / Black.
-
And when we finally add the solution to the milk, there is no colour change...
-
Indicating that there is no startch present in milk.
-
That concludes Experiment OB3A...
-
Experiment OB3B. Test a variety of foods for the pressence of reducing sugars.
-
As with all experiments involving he use of chemicals.
-
Safety glasses and gloves must be worn.
-
3 Food samples we are going to use today are: Milk, Glucose Solution and Water. Which is acting as our control.
-
The chemical involved is "Benedict's Solution." And it is added in equal volumes to each food sample.
-
The food samples are then heated in a water bath.
-
So, I'm going to add Benedict's Solution to each of the testubes...
-
You add an equal amount of Benedict's to the amount of liquid in the testube.
-
The testubes then need to be given a brief shake. To ensure that the liquids are fully mixed...
-
Experiment - OB3C. To test a food sample for the presence of fat.
-
Once again, we will need out Safety goggles and gloves.
-
This experiment involves: Rubbing the food sample on Brown paper.
-
I'm using butter, today. So, place a sample of butter onto the brown paper.
-
And then, Rub the food sample on the brown paper. And take off the butter afterwards...
-
And what we are looking for is, the presence of this spot. Which is known as a "Translucent" spot.
-
It's similar to a grease spot. And it allows light to pass through it, but you can't actually see through
-
the spot. And once you get that spot on the brown paper. That indicates the sample HAS fat in it.
-
If you don't get that spot. Then the food sample does not contain fat...
-
And that is the end of experiment OB3C...
-
Experiment - OB3D. To test a variety of foods for the presence of Protein.
-
Again, Safety goggles and gloves must be worn when handling chemicals in the lab.
-
Today, we will use 2 food samples. Water and Milk. The chemicals involved in this test...
-
Are "Sodium Hydroxide" and "Copper Sulfate."
-
The first stage involves adding Sodium Hydroxide to the food samples. And you must add aprox. an equal
-
volume of sodium hydroxide to the food sample being tested.
-
The testubes must be briefly shaken to ensure the chemicals are mixed.
-
And the last stage of this experiment involves adding a few drops of copper sulfate.
-
As you can see copper sulfate is a Blue chemical. And if there is protein present in the sample, It will
-
stain purple, when it meets the sample.
-
As you can see, there is no colour change in the testube containing the water. Which indicates there
-
is an Protein is absent in water. When added to the Milk...
-
We should get a purple colour appearing at the top of the solution. This indicates protein is present
-
in Milk. That is the end of experiment OB3D...
-
Experiment - OB5. To investigate the conversion of chemical energy in food into heat energy.
-
Safety goggles and gloves must be worn during this experiment.
-
We are going to use a cream cracker as our food source. And we are going to ignite the cream cracker...
-
And the chemical energy in the cream cracker, will be converted into heat energy. And will cause the
-
temperature of the water to rise...
-
Initally, the Temperature of the water is 23 oC. We will ignite the cream cracker using the bunsen burner.
-
As the cream cracker burns, it emits chemical energy in the form of heat energy. This energy is being
-
trapped by the water, and will cause the rise in temperature.
-
We will allow the cream cracker to completely burn itself out...
-
If we examine the temperature of the water in the testube, we will see it has risen from 23 oC to..
-
50 oC. A rise of 27 oC. This shows the conversion of chemical energy in food into heat energy.
-
Experiment - OB8. To investigate the action of the enzyme amylase on startch.
-
Safety goggles and Gloves must be worn as chemicals are involved.
-
Testube on the right contains startch and saliva. The one on the left contains startch and water.
-
Saliva contains an enzyme called amylase. And that enzyme breaks down startch into a product called...
-
Maltose. We will place the 2 testubes into a water bath at 37 oC for about 10 min.
-
We now remove the 2 testubes from the water bath and test both testubes for the presence of startch...
-
Using Iodine.
-
We add a few drops of Iodine into each testube.
-
The testube on the left, Iodine stays yellow / brown in colour. Indicating no startch present.
-
The testube on the right stains blue / back. Indicating the presence of startch.
-
From this experiment we can conclude that the amylase broke startch down into maltose.
-
Where as the other testube, which was acting as a control. The iodine stained blue / back...
-
indicating the presence of startch. That is the end of experiment OB8...