Practical work on food test. Activity 1.1.3 from understanding life science. Study the type of reaction on chemical used.

Here's a breakdown of the practical food tests, correcting some of the associations in your notes:

• Benedict's Solution

  • What it tests for: Reducing sugars (e.g., glucose, fructose, maltose). It does not test for starch or general carbohydrates.
  • Procedure: Add Benedict's solution to the food sample and heat gently in a water bath.
  • Positive result: The solution changes color from blue to green, yellow, orange, or brick-red, depending on the concentration of reducing sugar.
  • Notes' correction: Your notes incorrectly associate Benedict's with starch. Starch is a non-reducing sugar.

• Fehling's Solution (A and B)

  • What it tests for: Reducing sugars. Fehling's test is similar to Benedict's test.
  • Procedure: Mix equal parts of Fehling's Solution A and B, add to the food sample, and heat gently in a water bath.
  • Positive result: The solution changes color from blue to green, yellow, orange, or brick-red precipitate.
  • Notes' correction: Your notes incorrectly associate Fehling's with lipids, salts, and oils.

• Iodine Solution

  • What it tests for: Starch.
  • Procedure: Add a few drops of iodine solution directly to the food sample.
  • Positive result: The solution changes color from yellow-brown to blue-black.
  • Notes' correction: Your notes incorrectly associate Iodine with proteins.

Here are the correct associations for food tests:

• Benedict's Solution / Fehling's Solution: Tests for reducing sugars.
• Iodine Solution: Tests for starch.
• (Additional common tests not in your notes but relevant):
  • Biuret Test: Tests for proteins. Positive result is a color change from blue to violet/purple.
  • Emulsion Test: Tests for lipids (fats and oils). Positive result is a cloudy white emulsion forming when the sample is mixed with ethanol and then water.