The aim of this practical is to investigate on the different amounts of Vitamin C in a variety of juices and research on how it is affected when stored in its natural state or diluted.

Which type of fruit juice provides the most Vitamin C?

Aim

The aim of this practical is to investigate on the different amounts of Vitamin C in a variety of juices and research on how it is affected when stored in its natural state or diluted. To enable this, a reasonable amount of fruit juices ( apple, black-currant, lemon and orange)where all added into pre-prepared wells as this will help us find out which of the fruit juices mentioned above contained the most vitamin C. This practical will help develop key practical skills and improve data representation.

Introduction

Vitamin C (Ascorbic Acid) is an essential nutrient found in fresh fruits or vegetables like: lemons, oranges broccoli and Brussels sprouts. Vitamin C acts as an anti-oxidant to prevent plaque in the blood vessels and ensures that the central nervous system is functioning properly. Vitamin C is one of the most essential nutrients required for the body to function properly as it aids the formation of collagen which holds connective tissues together. Although this experiment does not oppose to any unethical issues, some may state otherwise due to fair trade as fresh fruits were used to carry out the investigation so alternative sources (Juices with artificial flavours) were also included in order to carry out the practical.

Structure of Ascorbic acid

Vitamin C can be separated into two main groups which are (Water-soluble and fat-soluble vitamins) these are mainly made up of vitamins C and B. Lack of vitamin C can lead to Scurvy, a common deficiency which causes muscle weakness, swollen and bleeding gums. Milder symptoms include tiredness, depression and bleeding under the skin which means wounds don’t heal as quickly as they should. Lack of Vitamin C can be treated through having a balanced diet and eating enough fruits (oranges, especially) and vegetables. As anti-oxidant, vitamin C bind free radicals in the body to prevent infections and illnesses like cardiovascular disease and cancer. However, a greater part of vitamin C is passed out in urine. Furthermore, Vitamin B is found in 8 different forms whilst vitamin C can be found in only one form which is Ascorbic acid. Vitamin C helps to maintain the elasticity of skin.

Variable

Predictions

It is predicted that the blue chemical found in the DCPIP will turn colourless or a pale pink to show the content of the fruit juice with the most Vitamin C. However, if a greater percentage of vitamin C solution is added to an agar gel plate, to test out this hypothesis, the procedure used to carry out the investigation will be less efficient.

Equipment List

Standard vitamin C solution (1%)
A wide variety of fruit juices
Clear rulers (for measuring the length of the pre-prepared wells)
DCPIP plates ...

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Variable

Predictions

Equipment List

Standard vitamin C solution (1%)
A wide variety of fruit juices
Clear rulers (for measuring the length of the pre-prepared wells)
DCPIP plates with pre-prepared wells
Pasteur pipettes
Measuring cylinders
Clear beakers
Cork borer
Dropping pipettes

Method

0.5% of Vitamin C solution is added to an agar plate with pre-prepared wells and is dissolved with 2 drops of fruit juice. It is then left for a short period of time; to enable the concentration of Vitamin C in the fruit juice to diffuse in the gel. This will result in a clear or pinkish circle around the wells. Each student was given an agar gel plate with 5 pre-prepared wells with their different percentages of fruit juice. The agar plates were in turn placed on the laboratory work surfaces and clearly labelled to avoid spillages and confusion when area of the circles were been measured and the results recorded. The averages of all 5 trails were calculated and recorded on a table of results and a graph for comparison.

Risk assessment, Safety precautions, and Ethical considerations

Justifying the validity and reliability of the chosen method

Repeats should be kept at a minimum and only repeated when necessary and students must familiarise themselves with the equipment before the start of every practical. Measurements taken should be accurate and students may cross-check with each other to avoid too many anomalous results. However, anomalous results should be investigated if they occur too frequently. Suitable apparatus and experimental procedures should be followed strictly to ensure valid results and precision and only the most precise equipment should be used to make the test fair and accurate.

Results

A table to show the area of colour change produced by solutions with varying vitamin C concentration %

Discussion of results

Data analysis

It was predicted that the fruit juice with the most Vitamin C concentration would be orange juice. However, this hypothesis was proven to be wrong and Lemon juice was shown to be the fruit juice with the most Vitamin C. Oranges which have a wide range of uses however, lemons expand on theirs all the way down to home remedies. They are used as common food sources and to cure illnesses like: Throat disorders, flu and certain skin conditions (Acne). Lemons are the most commonly used drugs in the world and renowned for their effectiveness. As shown on the graph the experiment results disagree with the prediction that apple and black-currant juices contain the most vitamin C as their contents had additional flavours and sweeteners. Unfortunately, there were no concentrated fruit juices to carry out a thorough investigation. However, when all 3 repeats were carried out on the lemon juice it tended to contain the most vitamin C.

Justifying the validity and reliability of the results collected

The results are valid and accurate because, a trial run was done before the practical was started. This was to ensure that there were no errors. In order to avoid errors in the experiment, the procedure was straight-forward and easy to follow. The results are reliable because they were 3 repeats and the measurements were cross-checked to ensure precision and to make it a fair test. Furthermore, only suitable equipment was used for the practical.

Limitations

One main limitation was lack of time and also the variety of juices, as a few contained less vitamins C so it was difficult to trace the concentration of vitamin C. This also meant the repeats were narrowed down only to 3.

Criticms of the data

Unfortunately more repeats were not possible due to the lack of fruit juices so it was difficult to observe any anomalies in the data. Callipers were not available during the practical so clear rulers were used instead which may have reduced the accuracy of the results recorded.

POTENTIAL ANOMALOUS RESULTS

Looking at the concentration of fruit juice on test two, the area of the circle is 0.5 whilst the repeats are both 1.33.This suggests that the results may be correct as the repeats are closer together which means the results are close to their true value.

Apart from the anomalous results, mentioned above, the results are valid although the orange juice didn’t not react to the concentration solution of Vitamin C there are still some sources of error even through the experiment was carried out carefully.

POSSIBLE SOURCES OF ERRORS

Even though there are no obvious anomalies it is important to consider the possibility of random errors. Although we aimed to cross-check every result due to insufficient time it was impossible.

Other sources of error are lack of concentration and personal bias and lack of callipers meant that the results may not have been as precise and accurate.

LIMITATIONS

One of the most common factors was lack of time and callipers were not available so the numbers of repeats were limited.

REDUCING ERRORS

Extra care should be taken when using Vitamin C solution and callipers should be used when repeating the experiment as it would improve accuracy. ‘Used’ agar gel plate should be labelled clearly so they are not disposed off or used carelessly when a separate group is carrying out the same practical.

CONCLUSION

In conclusion, the overall results disagree with the prediction that orange juice contains the most Vitamin C. This was due to the lemon juice been proven to contain the most vitamin C since it provided the most results when the Vitamin C solution was added to it and also lemon juice is most known for its medicinal purposes.

IMPROVEMENTS

Callipers will improve accuracy and also more repeats carried out in the practical will ensure reliability and the students would have more time to cross-check every measurement.

FUTHERWORK

It would be necessary to carry out the experiment using 2%of Vitamin C solution and also to repeat the 2nd and 3rd trials carried out earlier to produce more accurate results.

RESOURCES

As Salter’s’ Nuffield Biology

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