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Chemical Tests for Nutrients
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The Test for STARCH
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The Test for STARCH Reminder: Starch is a complex carbohydrate, which is our major source of food energy.
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The Test for STARCH Place a few drops of the unknown in a well on a spot plate
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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
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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
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The Test for STARCH The colours black, dark purple, or dark blue indicate starch is present
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The Test for STARCH The colours brown, yellow, or not changed, mean that there is no starch
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Test for Reducing Sugars
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Test for Reducing Sugars
Note: Glucose is a reducing sugar, so we use this as a test for glucose.
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Test for Reducing Sugars
This test requires heating in a water bath, at 40oC to 50oC for 5 minutes.
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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.
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Test for Reducing Sugars
Place about 5 mL of the unknown solution in a test tube.
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Test for Reducing Sugars
Place about 5 mL of the unknown solution in a test tube. Add about 10 drops of Benedict’s Solution.
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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
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Test for Reducing Sugars
If the solution turns orange after heating, the result is positive, and glucose is present.
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Test for Reducing Sugars
Other shades of orange or yellow can also mean that reducing sugars are present.
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Test for Reducing Sugars
If the solution stays blue after heating, the result is negative, and glucose is absent.
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Test for Reducing Sugars
A green or brownish colour can result if traces of glucose are present.
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Test for Reducing Sugars
A green or brownish colour can result if traces of glucose are present. (‘traces’ means very small amounts)
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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
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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.
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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.
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Test for Protein Place about 5mL of the unknown solution in a test tube.
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Test for Protein Place about 5mL of the unknown solution in a test tube. Add about 10 drops of Biuret Reagent.
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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.
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different positive results
Test for Protein If the solution becomes purple, violet, or lavender, it means that protein was present. different positive results
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Test for Protein If the solution stays pale blue, it means that there was no protein in the sample. Negative result
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Test for Fat
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Test for Fat Often called the grease spot test…. Bag of churros
Bag of samosas Greasy French Fries
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Test for Fat Often called the grease spot test….
Fat of any type will make paper translucent (light shows through), without drying up.
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Test for Fat Often called the grease spot test….
Simple, yet effective!
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Let’s recap:
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Let’s Recap: Starch Test:
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Let’s Recap: Starch Test: iodine turns from brown to black
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Let’s Recap: Starch Test: Glucose Test:
iodine turns from brown to black Glucose Test:
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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)
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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:
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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
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Let’s Recap And Finally Fat... The Grease Spot...
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Now you are all expert nutrient testers.
Next, The Lab!
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