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An investigation in to how enzyme ripeness in pineapple affects the setting of gelatine.

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Introduction

An investigation in to how enzyme ripeness in pineapple affects the setting of gelatine Gelatine, more commonly known as Jelly, is a substance that consists mainly of collagen, a protein found in animal tendons and skin. The gelatine used for cooking purposes is usually in the form of granules. These granules swell when they are re-hydrated in water, but only fully dissolve in hot water. As this solution cools it sets to a moisture holding gel. This gel forms due to the proteins in gelatine joining to form a web like structure. In Module 1 A-level Biology, we learn about the structure of a protein molecule. A protein molecule is formed when amino acids join together by condensation, forming a peptide bond and water as a bi-product. A chain of many amino acids is known as a polypeptide and a protein can consist of one or more of these. The opposite of condensation is hydrolysis. When hydrolysis occurs a peptide bond is broken and water is used up in the reaction. There are specific enzymes called proteases (Module 2), which can be found in fruits such as pineapple, that speed up the hydrolysis reaction that breaks down protein molecules. From research I have found that it is a protease called bromelain found in pineapple, which in the scenario is preventing the gelatine from setting by breaking up the proteins forming the web like structure. It is also in Module 1 that we learn how enzymes perform such tasks, and the conditions that best suit them. Enzymes are proteins which act as catalysts. They have a tertiary structure that provides them with an active site; a groove in the enzyme surface that combines precisely with a substrate of a specific shape and charge. ...read more.

Middle

Putting the dishes back in the fridge will prevent any bacteria or foreign bodies attaching to the jelly which could effect the results. I will start the timer the minute that I have placed the pineapple into the holes, and have a different timer for each petri dish so I know they have had exactly the same amount of time in the fridge. 6) After every 24 hours, I will remove them from the fridge again. From research I have done, I have found that enzymes in the pineapple will turn the gelatine from a gel to a liquid. I will measure the diameter of the area that is liquid and record my results in a table as below. Petri dish N A B C Hole number 1 2 3 Mean 1 2 3 Mean 1 2 3 Mean 1 2 3 Mean 1)Diameter before(mm) 2)Diameter after (mm) (2) - (1) mm Taking away the diameter of the hole at the start, from the diameter of the liquid and the hole, gives the diameter of the gel which has turned to liquid. I will use one of these charts every 24hrs for seven days, leaving me with seven mean results for each dish. When these diameters are plotted in a time/diameter graph they will allow me to see the rates at which the diameters have changed. Adding them will give me the mean total diameter of gel that has turned to liquid. As you can see from the table, I have used three holes for each type of pineapple so that I can work out an average. This reduces the effect of error and anomalous results. Results Table to show results and analysed data At the start, the holes are different sizes. ...read more.

Conclusion

With both of theses factors to consider, the results would have been fairer if the holes were the same size. A pestle and mortar were used to break up the pineapple flesh so that the enzymes available in the juice. However, it is possible that this process was different for each pineapple. If it had been carried out more thoroughly then more enzymes would be available which would cause a greater increase in hole size. If the petridishes were even slightly knocked when measuring the size of the hole then this mixed up the jelly with the liquid surrounding the hole and the contents of the hole. Mixing up these components would aid the reaction and make the measurements incorrect because the liquid will move further in the jelly as a results of being moved. It is possible that some of the measurements are incorrect because of this, which could cause anomalous results. Measuring the number of days after purchase may not be an accurate measure of the age of the pineapple and subsequently how old and ripe the pineapple is. This is because it is not known how long each of the pineapples had been on the shelf, so its possible that the pineapple tested 3 days after purchase is less ripe than the pineapple tested two days after purchase. The pineapples may have also been treated with a spray to prevent them ripening too quickly, and this may have reached some of the pineapples more than others. It may not be correct to make the conclusion that I have about the bromelain being associated with decay of the pineapples so that the seeds are exposed, because in this experiment the pineapples are commercially grown and seedless. For further work, I would like to use a seeded, naturally grown pineapple and compare the results. ...read more.

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