Benedict’s test for reducing sugars
| Benedicts Test for Reducing Sugars |
|---|
| Procedure for liquid: 1. add an equal volume of Benedicts solution to the sample in a test tube 2. Shake thoroughly 3. Place the test tube in a beaker of boiling water for 2-3 minutes |
| Procedure for solid: 1. add finely chopped sample into a test tube containing 2cm3 of denoised water 2. Shake thoroughly 3. Allow solids to settle 4. decant the liquid into another test tube 5. Add equal volume of benedicts solution into the test tube 6. Shake thoroughly 7. Place test tube in a beaker of boiling water for 2-3 minutes |
| Positive result: benedicts solution turns from blue to green/orange/yellow/red precipitate upon heating |
| Negative result: Benedicts solution remains blue upon heating |
| Solution remained blue | No reducing sugars |
| Solution turned from blue to green precipitate | traces of reducing sugars |
| solution turned from blue to yellow/orange precipitate | moderate amount of reducing sugars |
| solution turns from blue to red precipitate | large amounts of reducing sugars |
| Reducing Sugars | Non-Reducing Sugars |
|---|---|
| - glucose - fructose - Maltose - Lactose - Glyceraldehyde - Arabinose | - Stachyose - Sucrose - Tehalose - Verbascose - Raffinose |
Test for Starch
Add a few drops of iodine solution to sample on a white tile positive result iodine solution turns from yellow/brown/yellowish-brown to blue back negative result iodine solution remains yellow/brown/yellowish-brown
Alcohol Emulsion Test for Fats
| Alcohol Emulsion Test for Fats |
|---|
| Procedure for Liquid 1. add 2Cm3 of ethanol to a drop of the sample 2. Shake thoroughly 3. Add the solution to 2cm3 of water in a test tube |
| Procedure for Solid 1. add finely chopped sample into a test tube containing 2cm3 of ethanol 2. shake thoroughly 3. Allow solid to settle 4. Decant the liquid into another test tube containing 2cm3 of water. |
| Positive Result: A cloudy white emulsion is formed (remember to state the change) |
| Negative Result: Solution remains clear |
Biurets Test for Proteins
| Biurets Test for Proteins |
|---|
| Procedure for Liquid: 1. add an equal volume of sodium hydroxide to the sample in a test tube 2. add a drop of Copper(II)sulfate solution - shake after each drop OR 1. add an equal volume of biurets solution to sample in a test tube 2. shake well and allow mixture to stand for 5 minutes |
| Procedure for Solid 1. Add finely chopped sample into a test tube containing 2cm3 of deionised water 2. shake thoroughly 3. Allow solids to settle 4. Decant the liquid into another test tube 5. Add an equal volume of sodium hydroxide to sample in the test tube 6. add a drop of Copper(II)sulfate solution - shake after each drop |
| Positive Result: Solution turns from blue to violet |
| Negative result: Solution remains blue |