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Quantitative Determination of Food Colouring in Jelly Crystals using UV/Vis spectroscopy

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Quantitative Determination of Food Colouring in Jelly Crystals using UV/Vis spectroscopy Aim : To study specific food colouring agents that shows a specific colour . To study the principles of absorbance spectroscopy. To tabulate and analyse data from an Excel spreadsheet. Introduction Food colouring are mainly used in the food processing industry today as colour gives the food product certain flavours as people associate colours with certain flavours. Some is to stimulate a colour that is perceived by the consumer as natural food products. Food colouring also provides an identity to foods, to mask natural variations in colour, decorative or artistic purposes or to protect flavours and vitamins from being damaged by light. Electron transition occurs when valence electrons in a molecule are excited from one energy level to a higher energy level (Silberberg,2008). The energy change associated with this transition provides information about molecular properties such as colour. Ultraviolet-visible spectrophotometry or UV-Vis refers to absorption spectroscopy in the UV visible spectral region. The absorption in the visible range affects the perceived colour of chemicals used in food products involved. ...read more.


The filter funnel used was also rinsed a few times to ensure that no jelly crystals remained in the filter funnel. The volumetric flask was then make up to the mark with deionised water. Then a colouring agent with known concentrations was measured for 1ml,2ml,3ml,and 5ml and was placed in 50ml volumetric flask respectively. Each of the 50ml volumetric flask was then made up to the mark. The absorbance of each solution was measured using a spectrophotometer. The spectrophotometer was blanked with a cuvette filled with deionised water to 'zero' the spectrophotometer. The absorbance was first tested with the sample as the cuvette was filled to 2/3 of the capacity, then triplicate measurements was made with the same cuvette. This procedure was repeated for several times using other 4 conical flask with 1ml,2ml,3ml and 5ml of the colouring agent. Results Mass of jelly crystals weighed : 1.007g Table 1: Results obtained for absorbance of unknown sample of different concentrations and sample. Scan 1 Scan 2 Scan 3 Average Standard Deviation Absorbance Absorbance Absorbance Absorbance Absorbance Standard 1 (0.01nm) ...read more.


. As seen in Figure 1, it is possible to conclude that the results obtained was concordant to the actual value as absorbance is directly proportional to the concentration of the solution .Therefore, by using the equation from the graph , the concentration of the jelly crystal was 8.74x10-3M. From the value of the R2 which was 0.999, there was some errors that caused the graph from coming close to obtain a perfect linear regression. This could be due to the defects of some cuvette that disrupted the value ofabsorbance reading which could not be seen with the naked eye. Besides that , there could be an accumulation of air bubbles in the cuvette which would also affect the result obtained. Moreover , we could assume that not all the jelly crystals dissolved completely when diluted leaving small remnants that affected the value of concentration from the actual value. The spectrophotometer used could also have fluctuated reading over time (Silberberg,2008). Conclusion : The value of the absorbance increases directly proportional to the concentration of solution, thus obeying Beer Lambert law. The unknown concentration of the food colouring jelly solution is 8.74 x10-3M based from the linear regression obtained from the graph. ...read more.

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