Presentation is loading. Please wait.

Presentation is loading. Please wait.

Chemical Tests for Nutrients. The Test for STARCH.

Similar presentations


Presentation on theme: "Chemical Tests for Nutrients. The Test for STARCH."— Presentation transcript:

1 Chemical Tests for Nutrients

2 The Test for STARCH

3 n Reminder: Starch is a complex carbohydrate, which is our major source of food energy.

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

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

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

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

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

9

10 Test for Reducing Sugars

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

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

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

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

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

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

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

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

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

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

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

22

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

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

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

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

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

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

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

31

32 Test for Fat

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

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

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

36

37 Let’s recap:

38 Let’s Recap: n Starch Test:

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

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

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

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

43 Let’s Recap: n Starch Test: –iodine turns from brown to black n Glucose Test: –benedict’s turns from blue to orange with gentle heating (50 o C) n Protein Test: –biuret turns from blue to violet

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

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


Download ppt "Chemical Tests for Nutrients. The Test for STARCH."

Similar presentations


Ads by Google