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1.13 Core Practical - Investigating Macronutrients - Coggle Diagram
1.13 Core Practical - Investigating Macronutrients
Intro
We can perform special food tests to identify the presence of starch, reducing sugars,
protein, and lipids (fats and oils)
Practical
Nutrient being tested for..
Protein
Reagent/'Test
Biuret Test (Potassium hydroxide and copper sulfate)
Method
Add 1cm^3 of 40% potassium hydroxide to the food sample, and then add the same amount of 1% copper sulfate. Shake well and observe colour change if protein is present (blue -> violet)
Starch
Method
Add iodine solution to the food sample. If starch is present, the colour will change from orange to blue-black
Reagent/Test
Iodine solution
Lipids
Reagent/Test
Emulsion test
Method
Add 2cm^3 ethanol to food sample and shake thoroughly. Add 2cm^3 deionised water and shake thoroughly. If lipids are present, this will be indicated by the formation of a white emulsion layer at the top of the sample
Reducing Sugars
Method
Add 2cm^3 of the sample solution and 2cm^3 of blue Benedict’s solution to a test tube. Place in a boiling water bath for 5 minutes, or until there is no further change in colour. Presence of reducing sugar is indicated by a colour change to reddish-brown
Reagent/Test
Benedict's solution
How could we improve these experiments?
We should use a control in each experiment to ensure we know what a positive and negative result looks like
For example, a positive control for the Biuret test would be anything containing protein (e.g egg white) whereas a negative control would be a solution that does not contain protein (e.g distilled water)