Biological Tests
- Created by: Katiewillie
- Created on: 12-04-18 12:08
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- Biological Tests for...
- Starch
- Add Potassium Iodide to the solution
- If starch is present, solution will turn from yellow/brown to blue/black
- Reducing Sugars
- Benedict's Reagent
- Is an alkali solution of Copper II Sulfate.
- 1. Add equal amounts of liquid food sample and Benedict's Reagent
- 2. Heat in a gently boiling water bath for 5 minutes.
- If reducing sugars are present, solution turns brick red.
- Forms an insoluble precipitate of Copper I oxide
- Benedict's Reagent
- Non Reducing Sugars
- 1. Perform a Benedict's Test
- 2. If it is negative, hydrolyse the sample by heating with Hydrochloric acid
- 4. A second Benedict's test is performed and a positive result will be a Brick Red precipitate.
- 3. Neutralise the sample with Sodium Hydrogen Carbonate
- Proteins
- Biuret Test
- Add dilute Sodium Hydroxide and dilute Copper Sulfate to the sample.
- If proteins are present, a violet colour will be seen
- Lipids
- Add Ethanol to sample, shake, then pour into water
- If lipids are present then a white emulsion will appear at the surface
- Starch
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