1 / 45

Chemical Tests for Nutrients

Learn how to perform chemical tests for starch, reducing sugars, protein, and fat with step-by-step instructions and result interpretations.

fcooke
Download Presentation

Chemical Tests for Nutrients

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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!

More Related