Quantitative analysis of vitamin C in food products Essay

Quantitative analysis of vitamin C in food products Essay

There is growing evidence that Vitamin C serves as a potent antioxidant in vitro. There are many functions that Vitamin C has in the body among which is the capacity to improve the immunity system such that a person is more able to fight off colds and flus. Pre-Lab: List five other functions of Vitamin C in the human body. Vitamin C is another name for ascorbic acid. There is a marked similarity between the structure of glucose and Vitamin C. As a matter of fact, plants and most animals are able to synthesize Vitamin C from glucose. Unfortunately, humans are unable to do this and we must include Vitamin C in our diet or we risk a vitamin deficiency disease. We all recognize citrus fruits as a valuable vitamin C source, but few of us realize that many freshly harvested vegetables contain considerably more of this vitamin than do oranges or lime. Unfortunately, storage and processing destroy most of the Vitamin C in vegetables before they reach the consumer. Consumer cooking methods further decrease the amount of vitamin C in vegetables. Vitamin C is water soluble and thus leaches out while cooking or steaming. One useful analytical method for measuring the Vitamin C content of a vegetable or fruit involves an oxidation-reduction titration of ascorbic acid. In the titration, ascorbic acid is oxidized to form dehydroascorbic acid. You might think it unusual to oxidize the acid rather than titrate it with a base. However, biological samples contain many substances that also act as acids (as was mentioned in Experiment 3) and thus interfere in a titration of ascorbic acid with a base. In contrast, many fewer components of biological materials interfere with the oxidation of ascorbic acid by the oxidizing agent 2, 6-dichloroindophenol (DCP). Thus, an oxidation-reduction titration of ascorbic acid with DCP provides a more selective analysis than would an acid-base titration. Please note the equation for the reaction below: C6H8O6 (colorless) + C12H7O2NCl2(red) –> (pH3) C6H6O6 (Colorless) + C12H9O2NCl2 (colorless) This titration is specially convenient since DCP likewise serves as its indicator. Even as we add DCP solution to a simple solution containing Vitamin C, the response mixture remains to be colorless right up until all of the Supplement C has been converted to dehydroascorbic acid. The next drop of DCP solution added imparts a red colorization from excessive DCP to the mixture, implying both the assent point and the endpoint from the titration. (Expect solution to go from crimson to without color —–then on the endpoint reddish again). Mainly because DCP alternatives have a comparatively short life, we generally standardize this kind of solutions right away prior to with them. We can carry out the standardization conveniently simply by titrating aliquots of an ascorbic acid option prepared via an accurately-weighed sample of reagent-grade ascorbic acid. The standardization titration reaction is the same as the evaluation reaction over. In this try things out, you will begin by standardizing a DCP answer. Then you will certainly determine the vitamin C content of liquid and solid meals samples simply by titration with the standardized DCP solution. Prior to performing the titrations, you can expect to treat the food samples with metaphosphoric chemical p. Treatment with this acid solution serves to denature and precipitate aminoacids that would otherwise interfere with the analysis. Acidification of thesample also will serve to support the ascorbic acid, that may otherwise break down and be undetected. Acidification to pH lower than 4 likewise minimizes result of DCP with other compounds which in turn react with DCP only at pH levels greater than 4.

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