Nuffield Advanced Chemistry - It was suggested by my teacher to use pieces of fruit, boil them for different periods of time and then plot a graph to show the relationship between the amount of time boiling and the vitamin C content. The next step would be to add either lemon juice or HCl (??) to the fruit that was to be boiled as apparantly these protect the vitamin C and stop it from decomposing so in theory, boiling should not have such a great effect. I cannot, however, find where it is sugested that lemon juice/HCl protect the vitamin C? Also, do you believe it is a reasonable investigation to conduct?

Practical investigations

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It was suggested by my teacher to use pieces of fruit, boil them for different periods of time and then plot a graph to show the relationship between the amount of time boiling and the vitamin C content. The next step would be to add either lemon juice or HCl (??) to the fruit that was to be boiled as apparantly these protect the vitamin C and stop it from decomposing so in theory, boiling should not have such a great effect. I cannot, however, find where it is sugested that lemon juice/HCl protect the vitamin C? Also, do you believe it is a reasonable investigation to conduct?

Igloo writes ...

Your plans seem fine to me.

Lemon juice contains appreciable amounts of acids such as citric acid, but any acid should help to “protect” the vitamin C. This is because vitamin C is itself a weak acid, known as ascorbic acid. At a pH higher than 7, vitamin C undergoes a neutralisation, followed immediately by a rapid degradation. However, even in acidic conditions I would expect the vitamin C to degrade when boiled, though at a much slower rate. See if you can confirm this by experimentation. Remember that your experiments must be carried out very carefully, ensuring that all other variables are kept as constant as they can be whilst you alter the temperature. This includes your choice of fruit samples.

Always carry out a risk assessment and check with your teacher before starting any practical work.

Risk assessment
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updated: 31 January 2007

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