PT_Report

BIOLOGY PERFORMANCE TASK

A study into the browning process of avocados  __**ABSTRACT **__ This investigation aims to find out if the kitchen myth that avocado halves which contain the stone (the pit of the fruit) turn brown less quickly than the halves which do not contain the stone. An experiment was carried out on an avocado, cut into half, with the stone being left in one half.

The myth is true, as the avocado which did not contain the stone showed more signs of browning than the one which contained the stone.   __**INTRODUCTION **__ **AIM / OBJECTIVE ** The aim of this experiment is to determine if leaving the stone in one half of the avocado will slow down its browning process.

**INFORMATION ON AVOCADOS ** Avocados are fruits which originate from Mexico. Avocados contain a single seed, known as the stone, contained within its creamy flesh. Avocados are high in fibre, which might help to prevent high blood pressure, heart disease and certain types of cancer. Avocados also contain potassium, which lowers the risk of high blood pressure, heart attacks and cancer.

**OXIDATION OF AVOCADOS ** Avocados, like most other fruits, turn brown when left exposed to air in the open. This is because of a process called oxidation. The flesh of an avocado contains an enzyme, called polyphenol oxidase, which causes the avocado to oxidize when exposed to air. In the presence of oxygen, a chemical chain called o-quinones are produced, which creates black, brown or red pigments. This causes the fruit to develop a brown colour.

**HYPOTHESIS ** <span style="font-family: Arial,Helvetica,sans-serif;">The myth is true, and the avocado half which contains the stone will not turn brown as quickly as the half which does not contain the stone.

**<span style="font-family: Arial,Helvetica,sans-serif;">INDEPENDENT VARIABLE ** <span style="font-family: Arial,Helvetica,sans-serif;">- The presence of the stone of the fruit in one half of the avocado.

**<span style="font-family: Arial,Helvetica,sans-serif;">DEPENDENT VARIABLE ** <span style="font-family: Arial,Helvetica,sans-serif;">- The difference (if any) in the browning of the two halves of the avocado.

**<span style="font-family: Arial,Helvetica,sans-serif;">CONTROLLED VARIABLES **
 * <span style="font-family: Arial,Helvetica,sans-serif;">The environment in which the avocados are placed in must be the same.
 * <span style="font-family: Arial,Helvetica,sans-serif;">The two halves must come from the same avocado.

__**<span style="font-family: Arial,Helvetica,sans-serif;">METHODOLOGY **__
 * 1) <span style="font-family: Arial,Helvetica,sans-serif;">Cut one avocado into half.
 * 2) <span style="font-family: Arial,Helvetica,sans-serif;">Leave the stone in one half of the avocado.
 * 3) <span style="font-family: Arial,Helvetica,sans-serif;">Leave both halves to rest, in the same environment.
 * 4) <span style="font-family: Arial,Helvetica,sans-serif;">After 30 minutes, observe the avocado halves for any changes in the colour of the flesh.
 * 5) <span style="font-family: Arial,Helvetica,sans-serif;">Repeat Step 4 until at least one of the halves turn visibly brown.
 * 6) <span style="font-family: Arial,Helvetica,sans-serif;">Observe for any difference in the amount of browning in each half.

__**<span style="font-family: Arial,Helvetica,sans-serif;">RESULTS **__ <span style="font-family: Arial,Helvetica,sans-serif;">When the avocado was just cut open, both halves were of the same colour, as expected, as they were of the same avocado. <span style="font-family: Arial,Helvetica,sans-serif;">At 0 min

After two and a half hours, there was visible browning in both avocados. However, the avocado which did not contain the pit had more visible brown spots than the avocado which contained the pit.

<span style="font-family: Arial,Helvetica,sans-serif;"> At 2.5 hours

<span style="font-family: Arial,Helvetica,sans-serif;">As can be seen in the pictures, The avocado which contained the stone turned slightly brown in some areas, while the rest of the fruit still retained it’s original colour. However, the avocado which did not contain the stone had more visible browning, which occurred throughout the fruit.

<span style="font-family: Arial,Helvetica,sans-serif;">Therefore, I can conclude that the avocado which contained the stone turned brown slower than the avocado which did not contain the stone.

__**<span style="font-family: Arial,Helvetica,sans-serif;">DISCUSSION **__ <span style="font-family: Arial,Helvetica,sans-serif;">From the results, it can be seen that the myth and my hypothesis is confirmed. This is because the avocado which did not contain the stone showed more signs of browning (i.e. More brown spots throughout the fruit) than the half which contained the stone.

<span style="font-family: Arial,Helvetica,sans-serif;">This phenomenon might be due to the fact that the stone covers part of the avocado, thus reducing the surface area in which the avocado is exposed to the air. As explained above, the enzymes in the avocado will produce the o-quinones (which creates the brown pigments, causing the brown spots to appear on the flesh of the avocado) only when it is exposed to air. As the stone covers the surface area of the avocado, it will slow down the browning process, as the parts of the avocado which are not exposed to the air will not experience browning.

**<span style="font-family: Arial,Helvetica,sans-serif;">LIMITATIONS / FURTHER IMPROVEMENTS ** <span style="font-family: Arial,Helvetica,sans-serif;">Although there is evidence to prove that the browning is slowed down, leaving the stone in the avocado is not very effective, as the difference in the two halves are minimal.

<span style="font-family: Arial,Helvetica,sans-serif;">However, based on the same theory that the browning is slowed down because of the decrease in surface area of flesh exposed to air, the avocado could be wrapped with cling wrap instantly after cutting. This should be more effective than just leaving the pit in the avocado, as all the flesh will not have any exposure to air.

<span style="font-family: Arial,Helvetica,sans-serif;">If I had the luxury of more time to complete this project, I would have experimented using cling wrap. Although it sounds reasonable in theory, however, I would like to see if the theory works out in real-life.

__**<span style="font-family: Arial,Helvetica,sans-serif;">CONCLUSION **__ <span style="font-family: Arial,Helvetica,sans-serif;">Based on the results of this investigation, I have come to a conclusion that leaving the stone in a half of the avocado causes browning to be slowed down. Therefore, the myth and my hypothesis is confirmed. However, I feel that leaving the stone in the avocado is not the best way to prevent the avocado from turning brown. I think using other methods (e.g. cling wrap) will be more effective in preventing the browning process.

__**<span style="font-family: Arial,Helvetica,sans-serif;">REFERENCES **__ **<span style="font-family: Arial,Helvetica,sans-serif;">eSSORTMENT ** <span style="font-family: Arial,Helvetica,sans-serif; letter-spacing: 0px;">, Nutritional benefits of avocados, <span style="font-family: Arial,Helvetica,sans-serif;">[] <span style="font-family: Arial,Helvetica,sans-serif; letter-spacing: 0px;">, Assessed 17/7/10


 * <span style="font-family: Arial,Helvetica,sans-serif;">eHow.com **<span style="font-family: Arial,Helvetica,sans-serif;">, What makes Avocados Go Brown?, <span style="font-family: Arial,Helvetica,sans-serif;">[] <span style="font-family: Arial,Helvetica,sans-serif;">, Assessed 18/7/10

**<span style="font-family: Arial,Helvetica,sans-serif;">Wikipedia, the free encyclopedia, ** <span style="font-family: Arial,Helvetica,sans-serif; letter-spacing: 0px;">Avocado, <span style="font-family: Arial,Helvetica,sans-serif;">[] <span style="font-family: Arial,Helvetica,sans-serif; letter-spacing: 0px;">, Assessed 18/7/10 <span style="font-family: 'Times New Roman',helvetica,sans-serif;">