The unripe orange will have the highest concentration of vitamin C.

Oranges and Vitamin C

Vitamin C, or ascorbic acid, is the nutrient found in citrus fruits like oranges, grapefruit and lemons. The high amount of vitamin C in oranges makes it an ideal food choice as our body requires the vitamin. However, vitamin C in  oranges degrades over time. Oranges plucked earlier and kept in cold storage contain more vitamin C than oranges left to ripen on the trees. Similarly, freshly-squeezed orange juice is also known to lose its nutrients over time, unless refrigerated. Hence, oranges and orange juice need to be stored in a cool place to retain their vitamin C content.

The use of pesticides and fertilizers on oranges degrades the vitamin C found in the fruit, so pesticide-free produce may be a more nutritious choice. The type of containers used to store fruits can also be important in preserving its vitamin C content, with cardboard boxes lined with foil the best choice for storing oranges.
 

The hypothesis that the unripe orange will have the highest concentration of vitamin C has been proven to be true.

Vitamin C is an important part of our nutrition and is also an antioxidant. A lack of vitamin C in our bodies causes scurvy, a disease that causes teeth and bone abnormalities. Vitamin C can be found in abundance in fruits and vegetables, which are the main source of the vitamin for most of us. However, it is normally destroyed during cooking. Therefore, it is recommended to eat fruits and vegetables as raw as possible.
 

The science fair project may be repeated by using different types of fruits like papayas or apples.

The experiment may also be repeated by leaving the freshly squeezed juice in the open for a period of time, before testing for the gradual degradation of vitamin C.