University:
Eastern Kentucky University
Course:
CHE 111 | General Chemistry
Academic year:

2021
Views:

119

Pages:

2
Author:

Jameson Hunt

Introduction When a fruit or vegetable is cut and exposed to oxygen it begins to turn brown. The reason behind this is an enzyme called polyphenol oxidase. When polyphenol oxidase is exposed to oxygen brown pigments also known as melanin begin to form (Skibsted, Risbo & Anderson, 2010). Polyphenol oxidase is found to be increasing inactive as the pH is lowered (Sun, 2005). Polyphenol oxidase is also less active when refrigerated (Gibson & Williams, 2000) .Which is why most people keep fruits and vegetables in the fridge. Materials and Methods All procedures were carried out as outlined in Introductory to cell biology laboratory, BIOL 130L lab manual, pages 18-24 (Department of Biology, 2020). No deviations were made to these protocols. Results After the apple slices were place in on of four conditions, they were observed in 15minute intervals until three hours had passed. After the three hours had passed the final results were recorded. Table 1: Degree of browning after three hours Sample 2, room Sample 1, cold temperature temperature (4 (~22 degrees degrees Celsius) Celsius) +++ ++ Degree of browning at the end of three hours Ranking Most brown Second most brown Sample 3, no oxygen and ~22 degrees Celsius + Third most brown Sample 4, lemon juice and ~22 degrees Celsius - Not brown (+) Degree of browning (-) No browning Table 1 shows the results of the apple slices after three hours had gone by. Each (+) is representing the degree of browning on that sample. The more (+) the more the apple turned brown. The (-) represents that the apple slice did not turn brown. Discussion This purpose of this experiment was to demonstrate how to prevent enzymatic browning. In Table 1, sample 4 the lemon juice prevented the most enzymatic browning by not visibly browning at all. The apple slice appeared to look the same as it did at time zero (negative control group). This result was achieved because of the lemons low pH which causes the enzyme to become less active (Sun, 2005). The third most brown sample as seen in Table 1, is sample 3. This sample was to have no oxygen. Recall polyphenol oxidase reacts with oxygen to create melanin (Skibsted, Risbo & Anderson, 2010). The apple slice was in fact exposed to oxygen three times before it was supposed to be taken out. This of course was for the resulting pictures at time 15, 30 and 45. If no pictures were taken and the apple was not exposed to oxygen during this time there would be less browning. The sample placed in a 4 degrees Celsius atmosphere was the second most brown with the sample browning the most being left at room temperature. The colder setting was less brown because polyphenol oxidase is less active when refrigerated (Gibson & Williams, 2000).