Students use indicators to detect the presence of vitamin C (ascorbic acid) in popular fresh foods and drinks. In titration experiments students are able count the number of drops of the sample needed to change the indicator (indophenol) from dark blue to clear. Clear is an indication of the presence of vitamin C. Using this technique (counting the number of drops) we can rate the drinks in a comparative study for high/low vitamin C content. The positive control used is a super-saturated solution of crushed vitamin C tablets in distilled water. Sources of error include color additives and cloudy drinks which affected the color change in our indicator. Pictures of our work can be accessed at the bottom of the page.

In 1997/1998 five foods, in addition to drinks, were tested and found to be positive for vitamin C. They are listed below in descending order, from highest vitamin C concentration to lowest:

1. Orange

2. Broccoli

3. Lemon

4. Grapefruit

5. Lime

 

Results 1998/1999:

Out of 23 drinks tested, eleven tested positive for the presence of vitamin C. Our top 5 drinks for vitamin C are listed below in descending order, from highest vitamin C concentration to lowest:

1. Sunny Delight California Style Orange Juice

2. Mott's 100% Orange Juice

3. Hi-C Grape Drink

4. Hawaiian Punch Fruit Juicy Red Drink

5. Tropicana Original Home style Orange Juice

 

In similar studies, drinks which tested positive for vitamin C were found to significantly decrease in vitamin C content over a 6 day period when drinks were stored at room temperature.

 

Results 1999/2000:

Students were asked to bring in drinks they preferred with an emphasis on drinks that indicated a high concentration of vitamin C in their nutritional information labeling. 20 drinks were tested, 15 of which tested positive for the presence of vitamin C. Five did not contain a significant amount of vitamin C to test positive in our study. We tested two variables independently. First the drinks were titrated so that a comparative study could be done. We also used one drink that tested high for Vitamin C to see if the concentration of vitamin C would change over time.

 

Our top 5 drinks for vitamin C concentration are listed below:

1. Fruitopia, Kiwiberry Ruckus

2. Tropicana Pure Premier Orange Juice

3. Hawaiian Punch Juicy Red Fruit Juice

4. Sunny Delight Orange Juice

5. Super A Orange Juice

Click on graphs below to see a complete listing of our results.

Three Tropicana Pure Premier Orange Juice products were tested. They all were consistent in their vitamin C concentration; the OJ containing "extra vitamin C" and the OJ containing "extra vitamin C and calcium" tested slightly higher for vitamin C concentration than the "Original" product.

 

Vitamin C concentration over time:

Most outside studies indicate that vitamin C content both in the human body and in foods break down over time. Using a drink that tested high for vitamin C we repeated our test over a 10 day period. Tropicana Pure Premium OJ stored in the refrigerator at 10 C was found to significantly decrease in its concentration of vitamin C for each day following its purchase. (see graphs)

 

STUDENT GRAPHS: Results 1999/2000 study.

 

PHoTOGALLERY: See it here - our researchers hard at work, demonstrating some of their experiments.

 

 

More about Vitamin C: How vitamin C works (How Things Work - Web Site)

 

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