How Much Vitamin C is in Popular Juices?

Background
What is vitamin C?
Vitamin C is a water-soluble nutrient found in some foods. In the body, it acts as an antioxidant, helping to protect cells from the damage caused by free radicals. Free radicals are compounds formed when our bodies convert the food we eat into energy. People are also exposed to free radicals in the environment from cigarette smoke, air pollution, and ultraviolet light from the sun.
The body also needs vitamin C to make collagen, a protein required to help wounds heal. In addition, vitamin C improves the absorption of iron from plant-based foods and helps the immune system work properly to protect the body from disease.
How has this experiment been useful before?
Back in 2007 two New Zealand school girls used this experiment to compare the vitamin C content in Ribena to that of cheaper juices, they hypothesised that the vitamin C content in Ribena would be much greater but what they discovered shocked them. Instead of Ribena containing more vitamin C it was in fact the cheaper juices that had up to 4 times more vitamin C while Ribena had virtually none. This finding caused the company to withdraw sells of Ribena until it had the clearly stated amount of vitamin C on the cartons and a fine was given.

Plan
For this experiment we are just going to simply test how much juice it takes to de-colourise DCPIP. DCPIP is a blue chemical compound used as a redox dye. Oxidized DCPIP is blue, reduced DCPIP is colourless. We are going to test this with 3 different juices and pure vitamin C. The 3 different juices will be apple juice, Capri Sun, and pineapple juice. We will add 1cm^3 of DCPIP 4 different test tubes, the amount of DCPIP we use in each test tube will be our controlled variable because we do not want to change this amount. Our dependant variable would be the amount of juice/vitamin C it takes to decolourise the DCPIP. The independent variable is what we are using to decolourise the DCPIP, whether it is one of the 3 juices or the pure vitamin C.
Step 1: Add 1cm^3 of DCPIP to a test tube using a pipette.
Step 2: Fill a syringe with either the pure vitamin C or one of the 3 juices.
Step 3: Slowly drip the contents of the syringe into the DCPIP while stirring it. Do this until the DCPIP loses its colour.
Step 4: Using the markings on the syringe record how much juice or pure vitamin C was used.
Step 5: Repeat steps 1-4 for all juices and pure vitamin C 3 times so that you can record an average.
Hypothesis
I hypothesise that the pineapple juice or Capri Sun will contain most vitamin C out of the 3 juices because Capri Sun contains orange which is high in vitamin C and pineapple juice contains pineapple which is also high in vitamin C.

Results Fruit Juices/ Chemicals | Volume (cm3) of juice need to reduce 1cm3 of DCPIP 1 2 3 4 | Average Volume | Vitamin C | 0.2 | 0.3 | 0.1 | 0.2 | 0.2 | Apple Juice | 0.2 | 0.3 | 0.4 | 0.3 | 0.3 | Capri-Sun | 0.3 | 0.3 | 0.3 | 0.3 | 0.3 | Pineapple Juice | 0.2 | 0.1 | 0.2 | 0.2 | 0.17 |
This table shows all are readings and their averages but it would be