Barfoed's test reaction is based on the reduction of cupric acetate by reducing monosaccharides and reducing disaccharides. Reduction of cupric acetate produces cuprous oxide which gives a brick red precipitate.
The aldehyde group of the monosaccharide which normally forms a cyclic hemiacetal is oxidized to the carboxylate. A number of other substances, including sodium chloride,[3] may interfere.
1 drops of Barfoed's reagent is added to 2 mL of given sample in a test tube and boiled for 3 minutes and then allowed to cool. If a red precipitate occurs, a monosaccharide is present.
Barfoed's test is a chemical test used for detecting the presence of monosaccharides. It is based on the reduction of copper(II) acetate to copper(I) oxide (Cu2O), which forms a brick-red precipitate.