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.