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Chemical Tests for Nutrients

Chemical Tests for Nutrients. The Test for STARCH. The Test for STARCH. Reminder: Starch is a complex carbohydrate, which is our major source of food energy. The Test for STARCH. Place a few drops of the unknown in a well on a spot plate. The Test for STARCH.

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Chemical Tests for Nutrients

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  1. Chemical Tests for Nutrients

  2. The Test for STARCH

  3. The Test for STARCH • Reminder: Starch is a complex carbohydrate, which is our major source of food energy.

  4. The Test for STARCH • Place a few drops of the unknown in a well on a spot plate

  5. The Test for STARCH • Place a few drops of the unknown in a well on a spot plate • Add about 2 drops of Iodine Solution

  6. The Test for STARCH • Place a few drops of the unknown in a well on a spot plate • Add about 2 drops of Iodine Solution • Wait up to 30 secondsfor a colour change

  7. The Test for STARCH • The colours black, dark purple, or dark blue indicate starch is present

  8. The Test for STARCH • The colours brown, yellow, or not changed, mean that there is no starch

  9. Test for Reducing Sugars

  10. Test for Reducing Sugars • Note: Glucose is a reducing sugar, so we use this as a test for glucose.

  11. Test for Reducing Sugars • This test requires heating in a water bath, at 40oC to 50oC for 5 minutes.

  12. Test for Reducing Sugars • This test requires heating in a water bath, at 40oC to 50oC for 5 minutes. • The reagent used is called Benedict’s Solution.

  13. Test for Reducing Sugars • Place about 5 mL of the unknown solution in a test tube.

  14. Test for Reducing Sugars • Place about 5 mL of the unknown solution in a test tube. • Add about 10 drops of Benedict’s Solution.

  15. Test for Reducing Sugars • Place about 5 mL of the unknown solution in a test tube. • Add about 10 drops of Benedict’s Solution. • Place the test tube in a water bath, at a temperature between 40oC and 50oC for 5 minutes

  16. Test for Reducing Sugars • If the solution turns orange after heating, the result is positive, and glucose is present.

  17. Test for Reducing Sugars • Other shades of orange or yellow can also mean that reducing sugars are present.

  18. Test for Reducing Sugars • If the solution stays blue after heating, the result is negative, and glucose is absent.

  19. Test for Reducing Sugars • A green or brownish colour can result if traces of glucose are present.

  20. Test for Reducing Sugars • A green or brownish colour can result if traces of glucose are present.(‘traces’ means very small amounts)

  21. Test for Protein This is a molecule of albumin, the protein in egg white

  22. Test for Protein • The test for protein does not require heating, and so, could be performed either in a test tube, or on a spot plate.

  23. Test for Protein • The test for protein does not require heating, and so, could be performed either in a test tube, or on a spot plate. • In this presentation, we shall use test tubes. You may use spot plates in the lab.

  24. Test for Protein • Place about 5mL of the unknown solution in a test tube.

  25. Test for Protein • Place about 5mL of the unknown solution in a test tube. • Add about 10 drops of Biuret Reagent.

  26. Test for Protein • Place about 5mL of the unknown solution in a test tube. • Add about 10 drops of Biuret Reagent. • Mix and look for a colour change.

  27. Test for Protein • If the solution becomes purple, violet, or lavender, it means that protein was present. different positive results

  28. Test for Protein • If the solution stays pale blue, it means that there was no protein in the sample. Negative result

  29. Test for Fat

  30. Test for Fat • Often called the grease spot test…. Bag of churros Bag of samosas Greasy French Fries

  31. Test for Fat • Often called the grease spot test…. Fat of any type will make paper translucent (light shows through), without drying up.

  32. Test for Fat • Often called the grease spot test…. Simple, yet effective!

  33. Let’s recap:

  34. Let’s Recap: • Starch Test:

  35. Let’s Recap: • Starch Test: • iodine turns from brown to black

  36. Let’s Recap: • Starch Test: • iodine turns from brown to black • Glucose Test:

  37. Let’s Recap: • Starch Test: • iodine turns from brown to black • Glucose Test: • benedict’s turns from blue to orange with gentle heating (50oC)

  38. Let’s Recap: • Starch Test: • iodine turns from brown to black • Glucose Test: • benedict’s turns from blue to orange with gentle heating (50oC) • Protein Test:

  39. Let’s Recap: • Starch Test: • iodine turns from brown to black • Glucose Test: • benedict’s turns from blue to orange with gentle heating (50oC) • Protein Test: • biuret turns from blue to violet

  40. Let’s Recap • And Finally Fat... The Grease Spot...

  41. Now you are all expert nutrient testers. • Next, The Lab!

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