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Preliminary test:
We did a prelim test to find out the relative quantities of apple to use. To do this we tested 4 different quantities of apple until we found a suitable amount. We placed 1 test tube with 2mls of pectinase and 1 test tube containing 1 of the 4 measured amounts of apple into a water bath at the temperature of 40°. We left them in the water and placed thermometer into each of the test tubes so we could start our experiment as soon as they reached 40° this took approximately 2 minutes. When taking the temperatures of the test tubes I made sure I did not keep swapping the thermometers, as this would have lead to cross contamination. Once both the tubes had reached 40° we poured the pectinase into the apple and left them in the bath. Using a timer we left this solution in the bath for 10mins because I thought this would be a suitable time for the enzyme to work. Then I filtered the apple using a filter, filter paper and measuring cylinder then recorded my results.
Prelim results:
By looking at these prelim results I can see that I will not be using 3 or 5 grams, as they both do not produce enough juice for me to be able to do an accurate investigation. In my real test I will use 10grams of apple as this will make it easiest for me to record juice results and will make my test accurate.
Equipment used:
- Pectinase (2ml) ×18
- Apple (10grams) ×18
- Test tubes ×36
- Measuring cylinder
- Thermometer ×2 (one for pectinase and one for apple)
- Water bath set to 30º
- Water bath set to 37º
- Water bath set to 50º
- Water bath set to 70º
- Ice tub at the temperature of 5º
- Test tube rack
- A pair of scales
- Stop watch
- Spatula
- Filter
- Filter paper
Method:
- We placed 6 test tubes into the test tube rack, 3 containing 2mls of pectinase and 3 containing 10grams of apple. I measured them out using a measuring cylinder and a set of scales. We used 10 grams of apple because I found this was a suitable amount from my preliminary results. It produced enough juice for me to record an accurate measurement which is vital as otherwise I could not read and compare the different amounts for each temperature change.
- We then moved the test tubes to a place suitable for the temperature we were looking at e.g. water baths, ice bath etc and left them to get to the temperature of their surroundings. Using a thermometer in one of the pectinase test tubes and one of the apple test tubes I monitored the temperatures being careful not to swap the thermometers around so none of the pectinase got mixed with the apple.
- Once the test tubes had reached the temperature of their surroundings I poured 2mls of pectinase into each of the 3 test tubes and started the timer.
- When 10 minutes had gone by I took all 3 of the test tubes and filtered them into measuring cylinders to see how much juice they had collected.
- After the juice appeared not to be dripping through into the cylinder anymore I took all 3 readings, recorded them in my table and then found their average by adding them up and dividing the sum by 3.
Fair Test:
In my experiment my key variable was the temperature. The factors I kept constant were the amount of apple used, the amount of enzyme used and the time given. This made my experiment fair as I only changed one thing.
- I made sure I didn’t cross contaminate the pectinase and apple before I started the time by using a different thermometer in each test tube. If I had accidentally mixed them together before the stopwatch started this would have made my test unfair because the pectinase would have had a chance to start working on the apple.
- I kept the amount of apple and pectinase the same throughout the experiment because I only can change one thing at a time and in this investigation I am looking at temperature. If I had changed the amount of apple throughout my experiment I would have found the more apple I had used, the more juice would have been released. This would make my experiment unfair because I am trying to look at how the temperatre effects the amount of juice only.
- I also kept the time the same because it would have been unfair if one of my experiments had longer than another one for the pectinase to work in.
- I repeated the experiment 3 times and took the averages for each one. This was to make sure I got the most reliable set of results possible.
Results Table:
Conclusion:
I have found out that the temperature the pectinase worked best in and therefore produced the most juice was at 37ºc. From my graph I can see that from 37ºc the amount of juice produced dropped because the high temperatures denatured the pectinase. This means the enzyme molecules were destroyed/re-shaped and could not work efficiently to break down the apple. When the temperature reached 50ºc the amount of juice produced increased. I believe this was because the temperature was so high it actually broke down the fruit and had nothing to do with the enzymes breaking it down. My actual results do follow the trend of the results expected, so I am pleased with that. Unfortunately some of the points are spread far away from the general trend especially the point I have circled at 5ºc with a surprising amount of juice produced, this being 24ml. This is not what I predicted and it is not how it should look. Obviously something went wrong in my experiment here, this could be redone to try and overcome this mistake. Overall the results I got were fairly similar to what I predicted; the temperature the pectinase would work best in is 30º-40ºc. I predicted this because I knew that the enzymes in our body made up of proteins, work best at body temperature which is round about 37ºc and so the pectinase also made up of proteins should be similar.
Evaluation:
Overall I am happy with the way my experiment went. I got positive results which were similar to what I predicted and the way they should have looked. Of course there were some things that could have been improved:
- When the test tubes containing both pectinase and apple had been in one of the 6 temperatures for 10 minutes (the chosen amount of time) and were ready to be filtered into a beaker I found it hard to get them all out of the water baths and poured into the filters at the same time. In some of the hot temperatures some of the juice may have evaporated by the time I had filtered them, therefore altering my results. This could be improved by getting a partner to help me at this point in the experiment.
- As we did this experiment over a span of 2 lessons the apple we used in the first lesson was different in the second. The apple we used on the first day was more broken down than the second therefore it had more of a surface area for the pectinase to work on than the apple that was more compact. The smaller the particles of apple; the easier the pectinase can break it down. This could have affected our results so perhaps if I were to do the experiment again I would do it all with the same sample of apple.
