Vitamin C Test In The Citrus Fruits

Name: Ngau Jin Yuan

Ng Yuen Ping

Kiew Soon Yet

Jiven Raja A/L Silva Raja

Problem statement of experiment :

i. What is the significance of concentration in Vitamin C among orange, lemon and lime?

ii. Which of the citrus fruit juices has the highest Vitamin C concentration among orange, lemon and lime?

Objectives :i. To determine the concentration of Vitamin C in orange,

lemon and lime.ii. To determine the highest Vitamin C concentration

among orange, lemon and lime.

Introduction

Dropper, 100cm³ beaker, 10cm³ measuring

cylinder, test tube, test tube rack, a pair of forceps, squeezer, 100cm³ volumetric flask, stirrer, spatula, electronic balance, filter paper

Lemon, lime, orange, ascorbic acid, DCPIP powder, distilled water

Apparatus and Materials

From left to right : DCPIP solution , lime juice , orange juice , lemon juice and ascorbic acid

In this experiment, volumetric analysis method is used to determine

the concentration of vitamin C content in freshly squeezed citrus fruit juices.

Volumetric analysis is a common laboratory method of quantitative analysis that can be used to determine the concentration of a reactant.

A reagent of known concentration is used to react with the solution of the reactants.

The end point is the point at which the volumetric analysis is completed as determined by the colour change of an indicator.

The amount of reagent needed is recorded when the end point is reached.

Methodology

Method of drop by drop to reach the end point of the result

The end point is reached when a little drop of

DCPIP solution is needed to turn citrus fruit juices into a dark blue colour solution which is same colour as DCPIP solution.

When DCPIP solution is added into sample citrus fruit juices (orange, lemon and lime juices), the sample juices need more drops of DCPIP solution than ascorbic acid standard solution to reach the end point.

Observation

Ascorbic acid acts as a control in the experiment. Number of

mol of ascorbic acid is 0.568 mol dm-3. According to the number of drops of DCPIP solution in the fruit juices to reach the end point, orange, lemon and lime contain exceed 0.568 mol dm-3 of ascorbic acid.

Orange needs the highest number of DCPIP solution to reach the end point, therefore orange has the highest vitamin C content among the citrus fruits.

Lime needs the least number of DCPIP solution to reach the end point, therefore lime has the lowest vitamin C content among the citrus fruits.

Discussion

Decreasing vitamin C concentration (Orange > Lemon > Lime） However, the result obtained is different from the experiment conducted

by the FLINN SCIENTIFIC, INC(2008). From the vitamin C test by FLINN SCIENTIFIC, INC, the result stated that lemon has the highest vitamin C content, followed by orange and lime.

The difference of result in two experiments is due to the climate conditions of the citrus fruits plantations and production factors. Surrounding conditions like weather, sunlight and nutrients will affect the vitamin C content of the citrus fruits.

For example, in western countries, the citrus fruits may have lower concentration of vitamin C because of the cold weather. On the other hand, the citrus fruits in tropical countries may have higher concentration of vitamin C than those in the western countries.

Besides, different types of citrus fruits can also affect the vitamin C content in

the juices. Example : The experiment conducted above is using Sunkist

orange but the FLINN SCIENTIFIC, INC may use Navel orange. The different types of oranges will influence the vitamin C content in their juices.

Moreover, handling and storage of the citrus fruits will affect the vitamin C content in the two experiments.

Example : The citrus fruits under refrigeration will produce juices of different vitamin C concentration as the citrus fruits kept under room temperature.

The techniques handled in the experiment such as hand squeezing and blending may also affect the vitamin C concentration of the citrus fruit juices.

The higher the number of drops of DCPIP

solution in the citrus fruit juice, the higher the vitamin C content in the citrus fruit. Hence, the hypothesis is not accepted. Orange has the highest vitamin C concentration compared to lemon and lime.

Conclusion

1) Make sure that the citrus fruits are maintained at room temperature

throughout the experiment.

2) The DCPIP solution must be added slowly drop by drop into the test tube to avoid going past the end point.

3) Assure the freshness of the citrus fruits by making sure the fruits are freshly harvested and squeezed before carrying out the experiment.

4) Carry out the experiment immediately after the fruits are freshly squeezed to prevent oxidation of vitamin C in citrus fruit juices.

5) Avoid parallax error by placing your eyes perpendicular to the calibration mark of volumetric flask.

6) Various concentration of ascorbic acid standard solution such as 1.0 moldm-3, 1.5 moldm-3, 2.0 moldm-3 and so on can be used in conducting the experiment to obtain more accurate result.

Suggestions

Thank you