Enzyme Browning Lab Report

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Fruits and vegetables are very prone to enzyme browning caused by the enzyme polyphenol oxidase, or PPO when it reacts with oxygen. This browning occurs when the flesh of the fruit or vegetable is cut or bruised in anyway. This is most prominent in apples. The browning that occurs because of this enzyme is consider detrimental to both the aesthetic appeal and the overall taste of the apple. We were interested in determining if the rate at which this reaction occurs could be manipulated to speed it up or slow it down. We decided to test this by changing the pH at which the reactions took place. In other studies, that have been done, the optimum pH for PPO in other plant sources including apricots, peaches, grapes, and strawberries
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For pH 3 the average absorbance rate was 0.00551 ± 0.00527 %/min. The average absorbance rate was 0.00687 ± 0.00660 %/min for pH 7. With pH 11 the average absorbance rate was 0.00957 ± 0.00649 %/min. These results are shown in Figure 1.
Overall, the results found in testing the 3 pH solutions were similar. In all 3, the average change in absorbance rate increases as the pH went up. PPO + Catechol had the highest rates of absorption, while the control group of PPO only had on average the lowest rates of change in absorption, as seen in Figure 1.

Discussion According the results displayed in Figure 1. The absorbance rate increased as the pH increased. This was the same through the three types of experiments. These results do not support our original hypothesis. We predicted that that the two extrema pH s would slow down the rate of absorption, which turned out to not be true. What was true was that the rate of absorption at pH3 was the lowest out of the 3 pH tested. While the highest absorption rates occurred in a pH of 11, which was one of the extrema we tested. These results also do not support our prediction that pH 7 would be the level at which the rate of absorption would be the
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