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