Essay About Green Plants And Vitamin C Content

Vitamin C Content of Apple Juice
Vitamin C Content of Apple Juice
Introduction
Complete lack of ascorbic acid (a.k.a Vitamin C) in the diets of humans and other
primates leads to a classic nutritional disease, scurvy. This disease was widespread in
Europe during the fifteenth and sixteenth centuries, but it is rare today. Ascorbic acid is
widely distributed in nature, but it occurs in extremely high concentrations in citrus and
green plants such as green peppers and spinach. Ascorbic acid can be synthesized by all
plants and animals, with the exception of humans, other primates, and guinea pigs.
Therefore, vitamin C must be present in our dietary substances.
The fundamental role of ascorbic acid in metabolic processes is not very well
understood. There is some evidence that it may be involved in metabolic hydroxylation
reactions of tyrosine, proline, and some steroid hormones, and in the cleavage-oxidation
of homogentisic acid. Its function in these metabolic processes appears to be related to
the ability of vitamin C to act as a reducing agent.
The adult Recommended Daily Allowance f vitamin C is 70 mg per day. Some
scientists and physicians have suggested doses up to 1 to 3 grams per day in order to help
resist the common cold. Deficiency of vitamin C results in swollen joint, abnormal
development and maintenance of tissue structures, and eventually scurvy.
Determination of vitamin C in biological fluids such as bolld and urine is difficult
because only small amounts of the vitamin are present and many interfering reducing
agents are present. Substances containing sulfhydryl groups, sulfite, and thisosufate are
common in biological fluids and react with DCIP, but much more slowly than ascorbic
acid. The interference by sulfhydryl is often minimized by the addition of
p-cholormercuribenzoic acid.
Materials and Supplies
Apple Juice
Metaphosphoric acid/ Acetic acid solution 4%
Unknown ascorbic acid in metaphosphoric acid/acetic acid solution, .5mg/ml
2,6 dicholorphenolindophenol solution in water
Ascorbic acid oxidase, lyophilized water
Experimental Procedure
Standard Ascorbic Acid Solution
Fill a microburet with DCIP solution. Using a pipet, transfer 1.0 ml of the ascorbic acid
standard solution to a 50 ml Erlenmeyer flask containing 5 ml of 4% metaphosphoric acid
solution. Read and record the initial reading on the buret. Titrate by rapid, dropwise
addition of DCIP from the buret while mixing the contents of the flask. Add DCIP
solution until a distinct rose-pink color persists for 15-20 seconds. Record the final
reading on the buret. Repeat this procedure twice more, each time with a fresh 1.0 ml
sample of ascorbic acid standard. In a similar fashion, titrate three