Chemical Tests for Nutrients. The Test for STARCH.

Chemical Tests for Chemical Tests for

NutrientsNutrients

The Test for The Test for STARCHSTARCH

The Test for The Test for STARCHSTARCH

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

The Test for The Test for STARCHSTARCH

Place a few drops of the unknown Place a few drops of the unknown in a well on a spot platein a well on a spot plate

The Test for The Test for STARCHSTARCH

Place a few drops of the unknown Place a few drops of the unknown in a well on a spot platein a well on a spot plate

Add about 2 drops of Iodine Add about 2 drops of Iodine SolutionSolution

The Test for The Test for STARCHSTARCH

Place a few drops of the unknown Place a few drops of the unknown in a well on a spot platein a well on a spot plate

Add about 2 drops of Iodine Add about 2 drops of Iodine SolutionSolution

Wait up to 30 secondsWait up to 30 secondsfor a colour changefor a colour change

The Test for The Test for STARCHSTARCH

The colours The colours black, dark purple, or black, dark purple, or dark blue indicate starch is presentdark blue indicate starch is present

The Test for The Test for STARCHSTARCH

The colours The colours brown, yellow, or not brown, yellow, or not changed, mean that there is no changed, mean that there is no starchstarch

Test for Test for Reducing SugarsReducing Sugars

Test for Test for Reducing SugarsReducing Sugars

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

Test for Test for Reducing SugarsReducing Sugars

This test requires heating in a This test requires heating in a water bath, at 40water bath, at 40ooC to 50C to 50ooC for 5 C for 5 minutes.minutes.

Test for Test for Reducing SugarsReducing Sugars

This test requires heating in a This test requires heating in a water bath, at 40water bath, at 40ooC to 50C to 50ooC for 5 C for 5 minutes.minutes.

The reagent used is called The reagent used is called Benedict’s Solution.Benedict’s Solution.

Test for Test for Reducing SugarsReducing Sugars

Place about 5 mL of the unknown Place about 5 mL of the unknown solution in a test tube.solution in a test tube.

Test for Test for Reducing SugarsReducing Sugars

Place about 5 mL of the unknown Place about 5 mL of the unknown solution in a test tube.solution in a test tube.

Add about 10 drops of Benedict’s Add about 10 drops of Benedict’s Solution.Solution.

Test for Test for Reducing SugarsReducing Sugars

Place about 5 mL of the unknown Place about 5 mL of the unknown solution in a test tube.solution in a test tube.

Add about 10 drops of Benedict’s Add about 10 drops of Benedict’s Solution.Solution.

Place the test tube in a water bath, Place the test tube in a water bath, at a temperature between 40at a temperature between 40ooC C and 50and 50ooC for 5 minutesC for 5 minutes

Test for Test for Reducing SugarsReducing Sugars

If the solution turns orange after If the solution turns orange after heating, the result is positive, and heating, the result is positive, and glucose is present.glucose is present.

Test for Test for Reducing SugarsReducing Sugars

Other shades of orange or yellow Other shades of orange or yellow can also mean that reducing can also mean that reducing sugars are present.sugars are present.

Test for Test for Reducing SugarsReducing Sugars

If the solution stays blue after If the solution stays blue after heating, the result is negative, and heating, the result is negative, and glucose is absent.glucose is absent.

Test for Test for Reducing SugarsReducing Sugars

A green or brownish colour can A green or brownish colour can result if traces of glucose are result if traces of glucose are present.present.

Test for Test for Reducing SugarsReducing Sugars

A green or brownish colour can A green or brownish colour can result if traces of glucose are result if traces of glucose are present.present.

(‘traces’ means very small amounts)(‘traces’ means very small amounts)

Test for Test for ProteinProtein

This is a molecule of albumin, the protein in egg white

Test for Test for ProteinProtein

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

Test for Test for ProteinProtein

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

In this presentation, we shall use test tubes. In this presentation, we shall use test tubes. You may use spot plates in the lab.You may use spot plates in the lab.

Test for Test for ProteinProtein

Place about 5mL of the unknown Place about 5mL of the unknown solution in a test tube.solution in a test tube.

Test for Test for ProteinProtein

Place about 5mL of the unknown Place about 5mL of the unknown solution in a test tube.solution in a test tube.

Add about 10 drops of Biuret Add about 10 drops of Biuret Reagent.Reagent.

Test for Test for ProteinProtein

Place about 5mL of the unknown Place about 5mL of the unknown solution in a test tube.solution in a test tube.

Add about 10 drops of Biuret Add about 10 drops of Biuret Reagent.Reagent.

Mix and look for a colour change.Mix and look for a colour change.

Test for Test for ProteinProtein

If the solution becomes purple, If the solution becomes purple, violet, or lavender, it means that violet, or lavender, it means that protein was present.protein was present.

different positive results

Test for Test for ProteinProtein

If the solution stays pale blue, it If the solution stays pale blue, it means that there was no protein in means that there was no protein in the sample.the sample.

Negative result

Test for Test for FatFat

Test for Test for FatFat

Often called the grease spot test….Often called the grease spot test….

Bag of samosasBag of churros

Greasy French Fries

Test for Test for FatFat

Often called the grease spot test….Often called the grease spot test….

Fat of any type will make paper translucent (light shows through), without drying up.

Test for Test for FatFat

Often called the grease spot test….Often called the grease spot test….

Simple, yet effective!

Let’s recap:Let’s recap:

Let’s Recap:Let’s Recap:

Starch Test:Starch Test:

Let’s Recap:Let’s Recap:

Starch Test: Starch Test: – iodine turns from brown to blackiodine turns from brown to black

Let’s Recap:Let’s Recap:

Starch Test: Starch Test: – iodine turns from brown to blackiodine turns from brown to black

Glucose Test:Glucose Test:

Let’s Recap:Let’s Recap:

Starch Test: Starch Test: – iodine turns from brown to blackiodine turns from brown to black

Glucose Test:Glucose Test:– benedict’s turns from blue to orange benedict’s turns from blue to orange

with gentle heating (50with gentle heating (50ooC)C)

Let’s Recap:Let’s Recap:

Starch Test: Starch Test: – iodine turns from brown to blackiodine turns from brown to black

Glucose Test:Glucose Test:– benedict’s turns from blue to orange benedict’s turns from blue to orange

with gentle heating (50with gentle heating (50ooC)C) Protein Test:Protein Test:

Let’s Recap:Let’s Recap:

Starch Test: Starch Test: – iodine turns from brown to blackiodine turns from brown to black

Glucose Test:Glucose Test:– benedict’s turns from blue to orange benedict’s turns from blue to orange

with gentle heating (50with gentle heating (50ooC)C) Protein Test:Protein Test:

– biuret turns from blue to violetbiuret turns from blue to violet

Let’s RecapLet’s Recap

And Finally Fat...And Finally Fat...

The Grease Spot...

Now you are all expert nutrient Now you are all expert nutrient testers.testers.

Next, The Lab!Next, The Lab!