Objective:

• to detect reducing sugar
• to distinguish monosaccharides from reducing disaccharides

Principle of Barfoed’s test:

Barfoed’s test is used for distinguishing monosaccharides from reducing disaccharides. Monosaccharides usually react in about 1-2 minute while the reducing disaccharides take much longer time between 7-12 minutes to react with the reagent. Brick red color is obtained in this test which is due to formation of cuprous oxide.

Reagents for Barfoed’s test:

• test solution: 5 % Glucose, 5 % Sucrose, 5 % Maltose, 5 % Lactose, 5 % Starch
• Barfoed’s reagent: cupric acetate in 1% acetic acid
• Water bath
• Dry test tubes
• Pipettes

Procedure of Barfoed’s test:

1. Take 1ml of test sample in dry test tube.
2. Take 1ml of distilled water in another tube as control.
3. Add 2ml of Barfoed’s reagent to all the tubes.
4. Keep in boiling water bath.
5. Look for the development of brick red precipitate.
6. Note the time taken to develop the color.

Result interpretation of Barfoed’s test:

• Positive Barfoed’s test: development of brick red color ppt within 3-5 minutes
• Negative Barfoed’s test: absence of red color

** reducing disaccharides also give positive barfoed test on prolong heating

Barfoed’s Test: Objective, Principle, Reagents, Procedure and Result

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