Food Tests

• To test for lipids, add a liquefied food sample to filter paper and let it dry. If it dries and leaves no mark, it contains no lipids. If it dries and leaves a transparent stain, it contains lipids. Alternatively, add a liquefied food sample to a test tube. Add 2ml of ethanol and cover with a bung. Shale the text tube. If the solution goes cloudy white, it contains lipids.
• To test for glucose, add a liquefied food sample to a test tube. Add a few drops of Benedict's solution and swirl it gently. Place the test tube in a water bath at 75 degrees celsius and leave it for at least 5 minutes. Remove from the water bath and note any colour changes, If it remains blue, there is no glucose. If it changed to green, yellow, orange or red, it contains glucose.
• To test for starch, add a liquefied food sample to a test tube. Add a few drops of iodine solution and swirl gently. If it stays orange, there is no starch but if it becomes blue/black, starch is present.
• To test for protein, add a liquefied food sample to a test tube. Add a few drops of biuret reagent and shake well. Note any colour change. A purple colour indicates that proteins are present.