1. Killer milk? 4.7 How do we monitor food for safety?

2. Llanfair is an organic farm that delivers high-quality milk to a local dairy to be used as fresh milk or in milk products like yoghurt and cream. But someone is adding a poison to the milk. The dairy has been shut – losing lots of money for the farmer. Where is the poison being added? Let’s take a look at how the dairy processes fresh milk.

3. The lorry takes the milk to the dairy where it is stored in large refrigerated containers before it is processed. The cows are milked in an automatic parlour and the milk is collected in giant glass containers. The milk is delivered to local shops. The milk is processed and then sorted into fresh milk and milk that will be used to make yoghurt. The yoghurt is delivered to stores in the area. The milk is stored in large churns which are picked up by a lorry.

4. Copper crisis! Has something gone wrong at Llanfair Dairies? Some standard testing has found traces of copper in some of the produce. All Llanfair products have been suspended from sale and the farmer is losing a lot of money. Police need to establish what has happened and where.

5. Police chemists are testing each stage of the milk production to find out where the milk has been poisoned. How do they detect the poisonous copper when it is present in very small amounts?

6. Police chemists are testing each stage of the milk production to find out where the milk has been poisoned. How do they detect the poisonous copper - it is present only in very small amounts? First they take a sample of the milk and make it into a powder. This removes most of the water and concentrates any copper ions present.

7. Police chemists are testing each stage of the milk production to find out where the milk has been poisoned. How do they detect the poisonous copper - it is present only in very small amounts? First they take a sample of the milk and make it into a powder. This removes most of the water and concentrates any copper ions present. Then they dissolve it in sulfuric acid and filter it. This removes any protein and fat and leaves only soluble compounds.

8. Police chemists are testing each stage of the milk production to find out where the milk has been poisoned. How do they detect the poisonous copper - it is present only in very small amounts? First they take a sample of the milk and make it into a powder. This removes most of the water and concentrates any copper ions present. Then they dissolve it in sulfuric acid and filter it. This removes any protein and fat and leaves only soluble compounds. Then they add a few drops of sodium hydroxide solution. If any copper is present it will show as a green precipitate.

9. Police chemists are testing each stage of the milk production to find out where the milk has been poisoned. How do they detect the poisonous copper - it is present only in very small amounts? First they take a sample of the milk and make it into a powder. This removes most of the water and concentrates any copper ions present. Then they dissolve it in sulphuric acid and filter it. This removes any protein and fat and leaves only soluble compounds. Then they add a few drops of sodium hydroxide solution. If any copper is present it will show as a green precipitate. But where is any copper coming from? That is the question the police chemists need to answer.

10. Has it been given directly to the cows? Perhaps added to their food or sprayed onto the grass in their field? SampleResult Fresh milk at farmNo green precipitate

11. SampleResult Fresh milk in churnNo green precipitate Perhaps it has been added into the churns before the lorry picks them up?

12. SampleResult Fresh milk in dairy storageNo green precipitate Maybe it is a worker at the dairy?

13. SampleResult Fresh milkNo green precipitate Maybe it is added at the bottling plant?

14. SampleResult YoghurtGreen precipitate seen Or on the production line for the yoghurt?

15. Where should the police concentrate their enquiries? The lorry takes the milk to the dairy where it is stored in large refrigerated containers before it is processed. The cows are milked in an automatic parlour and the milk collects in giant glass containers. The milk is delivered to local shops. The milk is processed and then sorted into fresh milk and milk that will be used to make yoghurt. The yoghurt is delivered to stores in the area. The milk is stored in large churns which are picked up by a lorry.