Procedure for benzoquinone solution against its absorbance.

Procedure E: Conduct of experiment at different temperature1. Set up water bath at required temperature.2. Using a measuring cylinder, pour 50cm3 of distilled water into its respective 150ml beakers.3. Prepare the apple juice.4. Using a measuring cylinder, pour 50cm3 apple juice into its respective 150ml beakers.     Start timer when apple juice is poured into the beaker.5. Stir each solution with a glass rod.6. Attach the beaker to a retort stand and immerse it into the water bath.7. At every 10 minutes, use a dropper to transfer the solution to a cuvette.8. Measure the absorbance of respective solutions with a colorimeter at 430nm.9. Record data.The method of Least Squares was used to plot the calibration curve for benzoquinone solution against its absorbance. The relationship between the concentration of benzoquinone and the absorbance is linear. This method aided in the calculation of the gradient, y-intercept of the best fit line and the uncertainties.The quantities and  are used to label the value for the  axis and  axis respectively.Calibration curve of absorbance against concentration of benzoquinone was plotted to determine the unknown benzoquinone concentration from the oxidized apple juice.The best fit line derived was . The error bars for the absorbance values were too small to be seen. The gradient, , , has an uncertainty of 4.70%, which suggests that the method used to calibration curve was relatively accurate.Rate of reaction is defined as the change in concentration of a reactant or product per unit time, mol dm-3 time-1. Mathematically, rate of reaction can be determined by calculating the gradient of a tangent to a concentration-time graph. The graph showed a significant difference in the rate of reaction for the formation of melanin. From this graph alone solution with pH 5 was the most effective in slowing down the rate of formation of melanin in apple juice when exposed to air.The graph showed a significant difference in the rate of reaction for the formation of melanin. From this graph alone solution under the temperature of 90 was the most effective in slowing down the rate of formation of melanin in apple juice when exposed to air.Answering hypothesis: – The aim of this investigation was twofold:a. To find out the optimum pH that slows down the enzymatic process of apple, andb. How temperature affects the rate of formation of melanin in the enzymatic process of apple?Hence, the following presents the findings obtained from the research on the effects of varying pHs and temperature on the rate of formation of melanin in the enzymatic browning of apple.From the results, it was concluded that the optimum pH which generate the lowest rate of formation of melanin was pH 5, with rate of reaction of 1.70  10-3  mol dm-3 min-1. A reaction medium of pH lower or higher than pH 5 has a significant increase difference in the rate of reaction. Generally, the reaction of pH 5 and lower are lower as compared to the reaction of pH higher than pH 5. EFFECT ON PH ON HYDROGEN BOND. This suggests that the shape of polyphenol oxidase enzyme complements the least to the shape of the substrate at pH 5.  Generally, as temperature increases, the rate of reaction decreases slightly. However, at 75there is a sudden peak increase in rate of reaction. Suggesting chemical kinetics.  At 90, the rate of reaction drops very low comparatively to other temperature. BLANCHING OF APPLEHence, it was concluded that apple juice when expose to air at 90, will generate the least colour change of the juice. Suggesting that the polyphenol oxidase enzyme denatures at approximately 90.