Food Testing Methods - PDF

Starter – 5 mins On your mini white board. List the names of the tests for the different biological molecules: Glucose Starch Protein Lipid Bonus task – Can you state the positive and negative results for each test? Lesson – Testing an unknown sample. Lesson ou...

Starter – 5 mins On your mini white board. List the names of the tests for the different biological molecules: Glucose Starch Protein Lipid Bonus task – Can you state the positive and negative results for each test? Lesson – Testing an unknown sample. Lesson outcomes: Bronze – Recall the different food tests. Silver – Complete four different food tests. Gold – Identify the different biological molecules in the food.  Pestle & mortar Food testing Prepare the food sample. Place the food sample (bread) into the mortar and add a small amount of water. Then use the pestle to grind the food. Add 5 ml of water and mix. Fold the filter paper and place into a funnel. Filter the food sample (bread) into a small beaker. Food testing Use the test tubes and water baths to test for glucose. Use the spotting tile to test the samples for starch (iodine solution). Use the spotting tile to test for protein (biuret solution). Use the test tubes to test for lipids (emulsion test). Glucose & Starch Benedict’s test is used to test for simple Test for starch – Iodine solution sugars, for example glucose. test. 1. Prepare a sample of the food. 2. Put 5 ml of the food sample into a test 1. Prepare the food sample tube. 2. Place a small sample of the 3. Add 5 ml of Benedict’s solution, using a food on the spotting tile. syringe, and mix. 4. Place the test tube in a water bath at 3. Add 2 - 3 drops of Iodine 80oC for 10 mins. SOLUTION to the food 5. Record the colour after 10 mins. sample. Negative result (no glucose) – blue 4. Observe the colour change. Positive results: Negative result (no starch) – Low concentration of glucose – green/yellow orange/brown Medium concentration of glucose – orange High concentration of glucose – brick red Positive result – blue/black  Test for Protein Test of Lipid Biuret’s test Emulsion test 1. Prepare a 5 ml sample of the 1. Place a small spatula of the food. food sample in a test tube. 2. Add 5 ml of Biuret’s solution. 2. Add 5 ml of ethanol and shake (this will dissolve the sample). 3. Mix 3. Add 5 ml of water and mix. 4. Observe the colour change. 4. Observe the result. Negative result = solution Positive result = the solution will remains blue. turn cloudy white. Positive result = solution turns Negative result = the solution purple. will remain clear. Glucose & Starch Benedict’s test is used to test for simple Test for starch – Iodine solution sugars, for example glucose. test. 1. Prepare a sample of the food. 2. Put 5 ml of the food sample into a test 1. Prepare the food sample tube. 2. Place a small sample of the 3. Add 5 ml of Benedict’s solution, using a food on the spotting tile. syringe, and mix. 4. Place the test tube in a water bath at 3. Add 2 - 3 drops of Iodine 80oC for 10 mins. SOLUTION to the food 5. Record the colour after 10 mins. sample. Negative result (no glucose) – blue 4. Observe the colour change. Positive results: Negative result (no starch) – Low concentration of glucose – green/yellow orange/brown Medium concentration of glucose – orange High concentration of glucose – brick red Positive result – blue/black  Test for Protein Test of Lipid Biuret’s test Emulsion test 1. Prepare a 5 ml sample of the 1. Place a small spatula of the food. food sample in a test tube. 2. Add 5 ml of Biuret’s solution. 2. Add 5 ml of ethanol and shake (this will dissolve the sample). 3. Mix 3. Add 5 ml of water and mix. 4. Observe the colour change. 4. Observe the result. Negative result = solution Positive result = the solution will remains blue. turn cloudy white. Positive result = solution turns Negative result = the solution purple. will remain clear.