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Chemical Tests for Nutrients

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Presentation on theme: "Chemical Tests for Nutrients"— 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 seconds for 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

10 Test for Reducing Sugars

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

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

13 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.

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

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.

16 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

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

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

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

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

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

22

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

24 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.

25 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.

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

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

28 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.

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

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

31

32 Test for Fat

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

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

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

36

37 Let’s recap:

38 Let’s Recap: Starch Test:

39 Let’s Recap: Starch Test: iodine turns from brown to black

40 Let’s Recap: Starch Test: Glucose Test:
iodine turns from brown to black Glucose Test:

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

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

43 Let’s Recap: Starch Test: Glucose Test: Protein 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

44 Let’s Recap And Finally Fat... The Grease Spot...

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


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