Food tests template

Benedict's test in a beaker of boiling water on a tripod and gauze over a Bunsen burner, and biuret, iodine and ethanol emulsion tests in test tubes in a rack. GCSE / high school; A-level / AP / IB Biology.

What the template shows

• Test a food for reducing sugars, protein, starch and lipids
• Benedict's test
• Reducing sugars: food solution + equal volume of Benedict's, about 5 min in near-boiling water. Blue → green → yellow → brick-red precipitate as sugar increases
• Water bath
• Beaker of boiling water (or an electric water bath at about 80 °C). Point the tube away from people
• Bunsen burner
• Turn it off before the ethanol test: ethanol is flammable
• Biuret test (protein)
• Biuret reagent (or NaOH then a few drops of dilute CuSO₄), no heating. Blue → purple
• Iodine test (starch)
• A few drops of iodine solution. Orange-brown → blue-black (also works on a spotting tile)
• Emulsion test (lipids)
• Shake food with ethanol, then pour into water. A cloudy white emulsion means lipid
• Test tube rack
• Wear eye protection; compare each with a water control
• Reaction setup

Drawn with 18 shapes – every one editable in MolDraw.

Sources

• Nelson & Cox, Lehninger Principles of Biochemistry, 8th ed., 2021 Textbook
• Berg, Tymoczko, Gatto & Stryer, Biochemistry, 9th ed., 2019 Textbook