Food Test to Determine the Presence of Reducing Sugars and Non-Reducing Sugars Essay

Apparatus/Materials: – Bunsen burner – Solutions A, B, C, D, E, F and G (unknown) – Measuring Syringes – Stirring Rod – Beakers – Test tubes (7)plus holder and tray – Copper sulphate solution (CuSO4) – White dropping ray – tripod stand and mesh -stopwatch – Biuret? s solution – Sodium Hydroxide solution (NaOH) (or Potassium Hydroxide solution) – Hydrochloric Acid (HCl) – Sodium Hydrogencarbonate (NaHCO3) – Iodine Solution(I2) (or Potassium Iodide solution) – Ethanol (C2H5OH) – distilled water (H2O) Test Method Reducing Sugars 2cm3 of solutions A-G were placed into separate, labelled test tubes using separate measuring syringes. An equal volume (2cm3) of Benedict? s solution was then added to the solutions in the test tubes. The tubes were then gently shaken and placed in a water bath until any possible change in colour was noticed. Observation Inference/Explanation A- changed from a transparent bluish colour to purple. B- changed from a bluish colour to a yellow orange colour from the surface; middle began turning green; then entire solution turned bright orange in colour. C- turned from blue to a dark blue/purple. D- no reaction E- no reaction F- changed from a bluish colour to a yellow orange colour from the surface; middle began turning green;then entire solution turned bright orange in colour. G- no reaction. Benedict? s solution contains copper sulphate. Reducing Sugars reduce soluble blue copper sulphate, containing copper (II) ions (Cu2+) to insoluble red-brown copper oxide containing copper (I). The latter is seen as a precipitate. Therefore, solutions containing reducing sugars were: B and F. Those not containing reducing sugars were: A, C, D, E, and G. Test Method Observation Inference Nonreducing Sugars 2cm3 of solutions A-G were placed into separate, labelled test tubes using separate measuring syringes. 1cm3 of Hydrochloric (HCl) acid was then added to thesolution in the test tubes. The test tubes were placed into the water bath for one minute and were then neutralized with 2cm3 sodium hydrogencarbonate (NaHCO3). The Benedict? s test was then carried out (where an equal volume2cm3 -of Benedict? s solution was then added to the solutions in the test tubes. The tubes were then gently shaken and placed in a water bath until any possible change in colour was noticed. ). A- no reaction B- changed from a bluish colour to a yellow orange colour from the surface; middle began turning green; then entire solution turned bright orange in colour. C- no reaction D-changed from a bluish colourto a yellow orange colour from the surface; middle began turning green; then entire solution turned bright orange in colour. E- no reaction F-changed from a bluish colour to a yellow orange colour from the surface; middle began turning green; then entire solution turned bright orange in colour. G– changed from a bluish/ purple colour to a yellow orange colour from the surface; middle began turning green; then entire solution turned bright orange in colour. A disaccharide can be hydrolyzed to its monosaccharide constituents by boiling with dilute hydrochloric acid. Sucrose, for example, is hydrolyzed to glucoseand fructose, both of which are reducing sugars (and would give the reducing sugar result with the Benedict? s test) 2cm3 of solutions A-G were placed into separate, labelled test tubes using separate measuring syringes. An equal volume (2cm3) of sodium hydroxide solution were added to the solutions in the test tubes and mixed. Approximately two drops of Copper Sulphate solution was added and mixed. Observations were recorded. A- changed from a colourless solution to a purple/lilac colour. B- no reactio C-changed from a colourless solution to a purple/lilac colour. D- no reaction E- no reaction, but solution E floated above the added