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Vitamin C Investigation

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Introduction

Individual Investigation Hypothesis: Fresh orange juice has a higher vitamin C content than orange juice made from concentrate. Background Concentration, in biochemistry terms, is "increasing the strength or proportion of (a substance or solution) by removing or reducing the water or any other diluting agent or by selective accumulation of atoms or molecules." (Oxford English Dictionary). Therefore concentrated fruit juice has had its water removed (probably for ease of transportation) then had water re-added (reconstituted) before packaging. Vitamin C is an important part of the human diet. It is found in fruits, green vegetables and potatoes, and is "necessary for the formation of blood and bone and for resistance to infection." (Ramsden, 1995). It is an antioxidant which is capable of counteracting the damaging effects of oxidation. Vitamin C helps to prevent deficiency diseases, in particular scurvy, and is abundant in citrus fruits such as lemons, limes and oranges. Its chemical name, ascorbic acid, "is derived from a- and scorbuticus (Scurvy) as a shortage of this molecule may lead to scurvy." (www.chemie.de). The amount of vitamin C in a fruit juice can be estimated using a blue chemical die called DCPIP (common name 2,6-dichlorophenolindolephenol). It is reduced by an equal amount of vitamin C to a colourless, or sometimes pink, compound solution. ...read more.

Middle

Furthermore, vit C solution should be kept cool, as "the rate of oxidation increases rapidly with the temperature" (Ramsden, 1995). Once both solutions were freshly made the difference was obvious; the fresh DCPIP solution was blue rather than purple and the test worked much better. Care was taken when measuring solutions into test tubes by keeping them in the test tube rack on a flat surface. Solutions were measured accurately by keeping the pipette and syringe vertical, and all measurements were taken at eye-level. The amount of 'shake' given to the test tubes after each drop of solution was added is difficult to quantify, but it was kept to a reasonable degree of consistency. Due to time and buying constraints, it was only possible to purchase two brands of fresh orange juice. The decision was made to improvise, and use the juice of an orange, squeezed just prior to testing. This required additional equipment: pestle, mortar and a beaker. A few segments of the orange were placed in the mortar and crushed with the pestle until enough juice could be poured into the beaker, ready for use in the experiment. Whilst it would have been better to have used three brands of fresh orange juice, the freshly squeezed orange juice provided some interesting, unexpected results. ...read more.

Conclusion

Though there is no indication on the labels of any brand used in this experiment, it is possible that the juices have been through other processes. They may have been pasteurised, for example, to give them a longer shelf-life. This process, along with exposure to air, would decrease the vitamin C content of any juice. Another consideration would be the addition of ascorbic acid by the manufacturer. Again this is not apparent on the labeling. There may also be ways of "locking in" ascorbic acid so that it does not oxidise with exposure to air. One interesting finding was the vitamin C content of the fresh orange. Its juice was higher in vitamin C than any of the manufactured juices. Indeed, it contained more vitamin C than the ascorbic acid solution. A further investigation might test how long after a piece of fruit has been squeezed it starts to lose its vitamin C, or whether the type of container in which juice is kept effects the rate of loss. Perhaps experiments could be done with different light or temperature conditions. Nothing can really be concluded from this experiment, but it does seem to show that "fresh" orange juice cannot really be considered fresh, and that the best way for a juice to retain its vitamin C is to stay inside the orange. ...read more.

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