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Vitamin C in Fruit Juices

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INTRODUCTION
Vitamin C resembles a monosaccharide, but its structure has several unusual features. The compound has a five-membraned unsaturated lactone ring with two hydroxyl groups attached to the doubly bonded carbons[1]. This enediol structure is relatively uncommon. As a consequence of this structure feature, ascorbic acid is easily oxidized to dehydroascorbic acid. Both forms are biologically effective as a vitamin. There is no carboxyl group in ascorbic acid, but it is nevertheless an acid with a pKa of 4.17. The proton of the hydroxyl group is acidic, because the anion that results from its loss is resonance stabilized and similar to a carboxylate anion[2].

Humans and a few other vertebrates lack an enzyme that is essential for the biosynthesis of ascorbic acid from D-glucose. Hence ascorbic acid must be included in the daily diet of humans and these other species. Ascorbic acid is abundant in citrus fruits and tomatoes. Its lack in the diet causes scurvy, a disease that results in weak blood vessels, hemorrhaging, loosening of teeth, lack of ability to heal wounds, and eventually death. Ascorbic acid is needed for collagen synthesis.

Vitamin C -2D structure[3]

image00.png

AIM

The aim of this experiment was to see how different juices of the same brand have varying vitamin C content even though on the container it states the same RDI%(Recommended Daily Intake Percnetage).

HYPOTHESIS

It is hypothesised that the juices containing the larger amount of citrus fruit concentrate will have the larger vitamin C content.


EQUIPMENT & MATERIALS

  • Safety goggles/Lab coat
  • Four Fruit juices (100 mL)
  • Vitamin C standard solution (1.0 g/mL)
  • Starch solution (1%)
  • Iodine solution
  • Hydrochloric acid (HCl) 1M
  • Distilled water
  • 50-mL burette
  • Burette
  • Retort Stand and Burette Clamp
  •  10ml Graduated pipette and pumpette
  • 25-mL Graduated cylinder
  • Two 125-mL conical flasks
  • Two 100-mL beaker

PROCEDURE

  1.  A 10-mL graduated pipette was used to obtain 10.0 mL of the vitamin C standard solution, and placed in a flask. In a 25-mL graduated cylinder, 20 mL of distilled water was obtained and added to the vitamin C solution in the flask. This helped with the ease in observing for the endpoint because the water added did not enter into either the reaction or the calculations.
  1.  Two drops of 1M HCl, and 15 drops of starch solution were added to the vitamin C solution.
  1. The 50-mL burette was filled with iodine solution and secured in the clamp to. The 100-mL beaker was placed under the burette and the stopcock of the burette was turned to allow the air to be expelled from the tip. The waste beaker was set aside. The initial volume of the burette was recorded in TABLE 1 for trial 1 of the vitamin C standard solution.
  1. The conical flask containing the Standard sample of vitamin C was placed under the burette. Drop by drop, the iodine solution was added to the flask while swirling. The iodine was continually added and swirled, until the purple color was slow to go away. Then very carefully one drop was added and swirled. If the purple color disappeared within 15 seconds, another drop was added and swirled. This was done until the end point was reached.
  1. Steps 1-4 repeated for three additional trials. The data was recorded in the appropriate places on TABLE 1.
  1.  A clean dry 10-mL graduated cylinder and clean 125-mL conical flask was used, to repeat the  steps 1-5 for four trials of a 10.0 mL sample of fruit juice. The data was recorded in the appropriate places in the appropriate tables (TABLE 1-5). Four different samples of fruit juice were used which were manufactured by Golden Circle International.

RESULTS

TABLE 1 – Titration Data

Substance

Trail

Initial Burette Volume (mL)

Final Burette Volume (mL)

Iodine Used (mL)

Vitamin C Standard Solution (10.0mL)

1

0

33.81

33.81

2

0

33.83

33.83

3

0

33.68

33.68

4

0

33.80

33.80

Average

33.78

TABLE 2 – Titration Data

Substance

Trail

Initial Burette Volume (mL)

Final Burette Volume (mL)

Iodine Used (mL)

Golden Circle Tropical Punch (10.0mL)

1

0

25.70

25.70

2

0

25.64

25.64

3

0

25.66

25.66

4

0

25.60

25.60

Average

25.65

TABLE 3 – Titration Data

Substance

Trail

Initial Burette Volume (mL)

Final Burette Volume (mL)

Iodine Used (mL)

Golden Circle Golden Pash (10.0mL)

1

0

23.32

23.32

2

0

23.37

23.37

3

0

23.39

23.39

4

0

23.43

23.43

Average

23.38

TABLE 4 – Titration Data

Substance

Trail

Initial Burette Volume (mL)

Final Burette Volume (mL)

Iodine Used (mL)

Golden Circle  Pine Orange (10.0mL)

1

0

16.11

16.11

2

0

16.00

16.00

3

0

16.07

16.07

4

0

15.94

15.94

Average

16.03

TABLE 5  – Titration Data

Substance

Trail

Initial Burette Volume (mL)

Final Burette Volume (mL)

Iodine Used (mL)

Golden Circle  Orange Fruit Drink (10.0mL)

1

0

12.65

12.65

2

0

12.55

12.55

3

0

12.63

12.63

4

0

12.64

12.64

5

0

12.60

12.60

Average

12.61

CALCULATIONS

The RDI (Recommended Dietary Intake) for vitamin C in non-smoking adults is 60 mg, and 100 mg for smokers. For people suffering from cardiovascular disease, at least 100–200 mg of vitamin C appears to be needed. Many people may require higher doses, depending on their condition and environment in which they live. These therapeutic doses range from 500 mg to several grams in acute cases.[4]

Golden Circle Tropical Punch

average value of iodine used
for standard solution (mL)

=

average value of iodine used
for fruit juice (mL)

10.0 mg

x mg

33.78mL

=

25.65mL

10.0 mg

x mg

x mg

=

25.65mLimage01.pngimage01.png

                 33.78ml

=  7.59mg/10.0ml

=  0.759mg/ml

image04.png

Golden Circle Golden Pash

average value of iodine used
for standard solution (mL)

=

average value of iodine used
for fruit juice (mL)

10.0 mg

x mg

33.78mL

=

23.38mL

10.0 mg

x mg

x mg

=

23.38mLimage02.pngimage02.png

                 33.78ml

=  6.92mg/10.0ml

=  0.692mg/ml

image05.png

Golden Circle  Pine Orange

average value of iodine used
for standard solution (mL)

=

average value of iodine used
for fruit juice (mL)

10.0 mg

x mg

33.78mL

=

16.03mL

10.0 mg

x mg

x mg

=

16.03mLimage02.pngimage02.png

                 33.78ml

=  4.75mg/10.0ml

=  0.475mg/ml

image06.png

Golden Circle  Orange Fruit Drink

average value of iodine used
for standard solution (mL)

=

average value of iodine used
for fruit juice (mL)

10.0 mg

x mg

33.78mL

=

12.61mL

10.0 mg

x mg

x mg

=

12.61mLimage02.pngimage02.png

                 33.78ml

=  3.73mg/10.0ml

=  0.373mg/ml

image03.png

DISCUSSION:

Analysis

Results show that, in experimental conditions, all fruit juices contained more than the amount of vitamin C stated on the juice box per serve. The Golden Circle Tropical Punch had the largest amount of vitamin C containing 189.75mg per serve of juice. The Golden Circle Golden Pash came in second with 173.00mg per serve of juice. The juice with the third largest amount of vitamin C was Golden Circle Pine Orange with 118.75mg per serve of juice. The juice with least amount of vitamin C manufactured by Golden Circle was the Orange Fruit Drink. The reasoning behind this variation in vitamin C concentration can be directly attributed to the different fruit reconstituent. In the Golden Circle Tropical Punch there were four different reconstituents of citrus fruits with varying quantities of ascorbic acid, while the Golden Circle Golden Pash contained reconstituents of three fruits of which only two where citrus fruits. The other two juices, Golden Circle Pine Orange and Orange Fruit Drinks contained the least which was a surprising result because of the fact that both two types of juices both contained fruits with very high ascorbic acid levels. This suprising result can be attributed to the type of container it was stored in and the time difference between doing the experiments; this will be discussed more in depth in the error discussion. The hypothesis was partially correct as  the results indicated.

Error

According to Dr Nagy, in his Review of Vitamin C Contents of Citrus Fruit and Their Products, investigated what factors affected the vitamin C contents of citrus fruits and found vitamin C levels depend on six main factors[5]:

  • Production factors and climate conditions
  • Maturity state
  • Parameters used for processing into different products

Production factors and climate conditions: It has been discovered by researchers that high nitrogen fertilizer rates can lower vitamin C levels in citrus fruits. Furthermore, the climate in which it is grown, especially temperature affects vitamin C levels.  It was found that areas with citrus fruits with higher vitamin C levels. Areas with hot humid conditions were found to produce fruit with lower levels of vitamin C. This can be classed as a error because it is unknown if Golden Circle International source their fruit from and there could have been varying vitamin C contents in the fruit used and the early stages of production hence the surprising results found for the Pine Orange and Orange Fruit Drinks.  Although this error could not be avoided it still may have had an effect on the end result of the experiment

Maturity state: Vitamin C concentration decreases during the ripening process. Immature fruit has the highest levels because at a immature state citrus fruits contain more ascorbic acid hence the sour taste of un-ripened citrus fruits. This can be classed as a error because it is unknown if Golden Circle International source their fruit from and there could have been varying vitamin C contents in the fruit used and the early stages of production hence the surprising results found for the Pine Orange and Orange Fruit Drinks.  

 Parameters used for processing into different products: Frozen concentrated orange juice (FCOJ) and reconstituted FCOJ almost always have higher levels of vitamin C and is above the 100% US RDA values. This is most likely due to blending of early-season fruit with late season fruit. Canned single strength orange juice will have lower vitamin C levels due to heating during the canning process. NFC, Not -From-Concentrate, will vary due to the varieties being processed.

These can be classed as a error because it is unknown if Golden Circle International source their fruit from and  how they are produced, this could have caused varying vitamin C contents in the fruit used in the early stages of production hence the surprising results found for the Pine Orange and Orange Fruit Drinks.  Although this error could not be avoided it still may have had an effect on the end result of the experiment

There may have also been some experimental error which occurred mainly due to human reflex and judgment but other than that the experimental work went smoothly without a glitch.

CONCLUSION

In conclusion this experiment investigated the different juices of the same brand have varying vitamin C content. This was a very useful and interesting experiment which helped in the expansion of knowledge and helped clearly understand how vitamin C content can vary from the information given on the Nutritional Information. The results of my experiment, recorded over a four week period, illustrates that Golden Circle Tropical Punch contains the most vitamin C out of all Golden Circle juice products, which reinforces my hypothesis.


[1] Heyworth,R. (1984). Chemistry A New Approach. Macmillan, Hong Kong.

[2] Ascorbic Acid [online], Available at: http://www.inchem.org/documents/pims/pharm/ascorbic.htm, 27/10/2008

[3] The 3-D Structure of Vitamin C [online], Available at: http://www.heart-disease-bypass-surgery.com/data/molecular/m9.htm, 27/10/2008

[4] Vitamin C [online], Available at: http://www.yourhealth.com.au/index.php?page=/nutrients/view-content.php?id=161, 31/10/2008

[5] Vitamin C and Citrus Juices [Online], Available at: http://www.ultimatecitrus.com/vitaminc.html, 17/10/2008

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