Food Tests
Learning Objectives: To understand the main components of the
human diet. To test for the presence of starch, glucose
protein and fat in a food sample.
Starter: List the 7 parts of the human diet.
Carbohydrates
Water
Protein
Vitamins
Minerals
Fibre
Fats
8A What’s in food?
We can test foods to find out what chemicals they contain.
Orangey-brown iodine turns blue-black when it reacts with starch.
drop iodine solution onto the food
black = starch
8A What’s in food?
Blue Benedict’s solution turns orangey-red when it is boiled with glucose.
blue turns orange/red= glucose
heat
chopped up food
hot water
8A What’s in food?
In the Biuret test the solution turns purple.
chopped up food
potassium hydroxide
shake
coppersulphate
purple = protein
8A What’s in food?
Fats go cloudy white when they are mixed with ethanol and water.
Now see if you can use these tests to identify the food chemicals on the next slides.
grind food with ethanol
add waterfilter
cloudy = fat
8A What’s in food?
For each food, decide on the chemicals found in them.
Fats Protein Starch Glucose
Food sample Test ResultIodine solution orangey-brown
Benedict’s test blue
Biuret test purple
Ethanol test cloudy white
8A What’s in food?
For each food, decide on the chemicals found in them.
Fats Protein Starch Glucose
Food sample Test ResultIodine solution blue-black
Benedict’s test blue
Biuret test blue
Ethanol test clear
8A What’s in food?
For each food, decide on the chemicals found in them.
Fats Protein Starch Glucose
Food sample Test ResultIodine solution orangey-brown
Benedict’s test orangey-red
Biuret test blue
Ethanol test clear
8A What’s in food?
For each food, decide on the chemicals found in them.
Fats Protein Starch Glucose
Food sample Test ResultIodine solution orangey-brown
Benedict’s test orangey-red
Biuret test blue
Ethanol test clear
Practical Activity
Safety First:Wear safety
gogglesStand upTuck your chair &
bags under your desk
Tie back long hair
Experiment!
You’ve been given a sample of foods. Test these foods using the four food tests to see what energy chemicals they contain!
Complete this table with your results.
Food Starch Glucose Protein Fat
Cream Cake
? ? ? ?
1. A balanced diet…
a) contains the same amounts of the main food groups
b) contains healthy amounts of the main food groups
c) doesn’t fall off the table.
2. A balanced diet for most people has more…
a) fat than water
b) carbohydrate than protein
c) crisps than fruit.
8A A food test for YOU!
3. To test for protein in food you…
a) add iodine solution
b) do the Biuret test
c) poke it with a big stick.
4. Sugar and starch are both…
a) proteins
b) fats
c) carbohydrates.
8A A food test for YOU!
5. Iodine solutions turns blue-black with…
a) starch
b) protein
c) age.
6. A food went orangey-red when it was boiled with Benedicts solution. It could be…
a) a carrot
b) a boiled sweet
c) a sausage.
8A A food test for YOU!
Food Tests
Learning Objectives:
To understand the main components of the human diet.
To test for the presence of starch, glucose protein and fat in a food sample.
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