The Vitamin C Content of Fruit Juice

IntroductionVitamin C, also known as ascorbic acid, is an essential nutrient for humans and other animal species. It needs to be present in the body, and it acts as an anti-oxidant, protecting the body from oxidative stress. It also prevents the symptoms of scurvy, which is caused by the lack of vitamin C and causes the gums to blister and the teeth to fall out. Using this experiment, I am going to find out how much vitamin C is in a variety of fruit juices.

MethodSecure a burette in a clamp stand, so that there is enough space below it for a test tube. Into the test tube, measure out 1cm3 of 1% DCPIP solution using a pipette. Pour some 1% vitamin C solution into the burette, using a funnel. Then drip this into the DCPIP solution, shaking the test tube gently after each drop. Record how many drops of vitamin C it takes to turn the blue DCPIP clear, then repeat the whole experiment using clean equipment, and take an average of the results. Once this is completed, replace the vitamin C solution with one of the various fruit juices, and repeat the procedure exactly, using 1cm3 of DCPIP for each juice. Repeat and take an average of each one.

Raw Data(See attached sheet)

Results Table

Concentration Table

Name Amount taken to decolourise 1cm3 of 1% DCPIP solution (cm3)Test 1 Test 2 Test3 Average

Ascorbic acid 3.2 1.5 1.6 2.1

Apple juice 4.8 2.6 3.2 3.5

Orange juice 3.0 2.6 3.4 3

Cranberry juice 4.2 4.5 3.7 4.1

Grapefruit juice 2.7 5.3 2.9 3.6

NameConcentration of Vitamin C- (mg/cm3)

Ascorbic Acid 0.48

Apple Juice 0.29

Orange Juice 0.30

Cranberry Juice 0.24

Grapefruit Juice 0.28

Graph(See attached sheet)

ConclusionIn conclusion, these results have shown that orange juice has the highest vitamin C content, with 0.30mg/cm3. Second is apple juice, which is unexpected because grapefruit juice would seem to have more vitamin C in because it is a citrus fruit. This is probably due to an anomalous result of 5.3cm3 of grapefruit juice required to decolourise 1cm3 of DCPIP solution, which would push the average up significantly, effecting the concentration results. I would have expected apple juice to have the same or a lower vitamin C concentration than cranberry juice, because it is not a citrus fruit, and for the other results collected, it took a large number of drops to make any noticeable difference at all.

EvaluationI think that this experiment was a success, because it showed that orange juice has the highest vitamin C content of the four juices, which was the expected result. However, there were a number of anomalous results in the experiment that have affected the final conclusion. This kind of error could have been avoided by doing more repeats of the experiment, reducing the effect of any anomalous results on the average. Also a computer-controlled way of measuring the colour change could have been used, to avoid any human error in the observation of the decolourisation of the DCPIP.