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Analysing the vitamin C content in different fruit juices

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Introduction

Title : The Vitamin C Content in Fruit Juices Name : Yii Seng Ong Date : 28 August 2011 Class : 12M15 Student ID : 2011200378 Name of lecturer : Madam Ida Muryany binti Md. Yasin Objective 1. To determine and compare the concentration of vitamin C in different kind of fruit juices 2. To determine and compare the concentration of vitamin C in freshly prepared fruit juices and carton fruit juices Introduction 1. Vitamin C Vitamin C or also can be known as ascorbic acid is the elonic form of 3-oxo-L-gulofuranolactone. It can be synthesized from glucose or extracted from other plant sources such as blackcurrants, rose hips or citrus fruits. The empirical formula for vitamin C is C6H8O6. Other than that, the molecular weight for ascorbic acid is 176.1. Its melting point is about 190°C( with decomposition). The appearance is white to slightly yellowish crystalline powder. It is practically odourless, with a strong acidic property and a sour taste. Figure 1 : 2D structure of vitamin C Figure 2 : 3D structure of vitamin C Generally, vitamins are a group of complex organic compounds which play an essential role in animal metabolic process but which the animal cannot synthesis. Vitamins do not provide energy however, in their absence the animal develops certain deficiency diseases or other abnormal conditions. Vitamins together with proteins, carbohydrates, fats and mineral salts are essential components of the food of animals. Certain animals can synthesis certain vitamins. All animals which need vitamin D can synthesis it from ergosterol in the presence of UV light. With the exception of vitamin D, human body cannot make its own vitamins and some cannot be stored. Therefore, one must obtain vitamins from a food on a daily basis. A person’s diet must provide all the necessary vitamins. Vitamin C is a water-soluble vitamin, meaning human’s body does not store it. We get what we need, instead, from food. ...read more.

Middle

8. The results are tabulated in Table 1. 9. A graph (Graph 1) of volume of vitamin C solution needed to decolourise DCPIP solution against concentration of vitamin C solution used( standard curve graph of vitamin C) is plotted. 1. To determine vitamin C content of freshly prepared fruit juices and carton fruit juices 1. Oranges, limes and lemons are cut and squeezed into 3 separate beakers which are labeled correctly. 2. 0.5ml of DCPIP solution is placed into a boiling tube using a syringe. 3. 3ml of freshly prepared lime juice is sucked into another syringe and added drop by drop into the DCPIP solution. 4. The mixture is shaked gently while lime juice is added continuously until the blue DCPIP solution is decolourised. The volume of lime juice used is recorded. 5. Steps 1 to 4 are repeated to obtain an average volume of lime juice used. 6. Steps 1 to 5 are then repeated using freshly prepared orange juice, freshly prepared lemon juice, carton lime juice, carton orange juice and carton lemon juice. 7. The results are tabulated in Table 2 for fresh fruit juices and in Table 3 for carton fruit juices. 8. The concentration of vitamin C in each sample of fruit juice ( 6 samples) are calculated using the formula below. Volume of fruit juice required to = k decolourise DCPIP solution concentration of vitamin C in fruit juice while k = constant 1. The concentration of vitamin C in each sample that is calculated are also tabulated in the same table. Results A) Concentration of vitamin C solution (g/100ml) Volume of vitamin C solution used to decolourise DCPIP solution (ml) Trial 1 Trial 2 Trial 3 Average 1.000 0.4 0.3 0.2 0.3 0.750 0.6 0.5 0.7 0.6 0.500 0.8 0.8 0.8 0.8 0.250 0.9 1.1 1.0 1.0 0.125 1.1 1.2 1.0 1.1 Table 1 Graph 1: Graph of volume of vitamin C solution needed to decolourise DCPIP solution against concentration of vitamin C solution used V = ...read more.

Conclusion

To ensure the reliability of results, each experiment should be repeated at least twice. The average value of volume of each fruit juice or vitamin C solution is calculated by dividing the sum of all the reading for that particular fruit juice with the number of readings taken. By repeating the same procedure, random errors such as parallax error can be minimized and at the same time, the vitamin C content of each fruit juice can be determined more accurately and may be closer to the theoretical value. Safety precautions 1. Care should be taken while cutting the fresh fruits. During the extraction of juices from the fruits, fruits should not be pounded to hard. It is because the heat produced will destroy part of the vitamin C in the juices. 2. The fruit juices should not be prepared a day earlier before the experiment or exposed to the air for a day because the vitamin C in fruits is easily destroyed by oxidation. 3. Care should be taken not to shake the tube vigorously while the vitamin C and fruit juices are added. This is because the oxygen from the atmosphere will oxidize the DCPIP solution to become blue again. If this happens, more fruit juice is needed to reduce the DCPIP solution. Therefore, the actual vitamin C content in fruit juice cannot be determined accurately. 4. In order to prevent confusion, all the beakers used should be labeled with the name of fruit juice contained. This is due to the fact that colour and smell of the lime juice and lemon juice are quite similar. Conclusion The lower the volume of fruit juice used to decolourise the DCPIP solution, the higher the concentration of vitamin C in the fruit juice. 1. The fresh orange juice has the highest concentration of vitamin C among the fruit juices tested. 2. Freshly prepared fruit juice has higher concentration of vitamin C compared to carton fruit juice. Hypothesis is accepted. Reference 1. http://www.umm.edu/altmed/articles/vitamin-c-000339.htm 2. http://www.beta-glucan-info.com/vitaminchistory.htm, Beta Force The Only Answer, Unknown author. 3. http://www.coursework.info/ ...read more.

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A very detailed account of the investigation written in a concise style. A clear understanding of background theory demonstrated with A level terminology used throughout. Data presentation and analysis is of a high standard.

Marked by teacher Adam Roberts 17/09/2013

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