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The use of pectinase in fruit juice production

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The use of pectinase in fruit juice production Introduction Pectinase is an enzyme which catalyses the breakdown of pectin in the cellulose cell wall in the plant cells. Pectin is a sticky polysaccharide which is embedded in the cell wall of the plant cells to hold cellulose together in place. It is the structural carbohydrate which gives the plant cell mechanical support and prevents the cell from bursting when water enters into the cell by osmosis. It is also insoluble due its structure and arrangement of its monomers which are simple sugars. The presence of pectin in the cellulose cell wall prevents the cell contents from leaving the cell. This minimises the yield of the fruit juice when the manufactures try to extract juice from fruit. Pectinase, like many enzymes, is a globular protein and its structure is maintained by hydrogen bonds, disulphide bridges and the ionic bond. Enzyme has a specific site called the active-site where substrate molecules bind to form enzyme-substrate complex. The shape of the active-site is so specific that only substrate which has a complementary shape can fit in. This is called lock and key mechanism and suggests that one enzyme can only catalyse one reaction. However, enzyme slightly changes its shape when substrate binds to its active- site. This process is known as an induced fit. Enzyme speeds up the rate of reaction by lowering the activation energy. ...read more.


The graph for the mixture with pectinase is a curve, the gradient of which is big at the beginning of the reaction and then the gradient becomes smaller for the rest of the reaction. The mixture without pectinase produced no apple juice so the graph is a horizontal line along the time axis. This indicates that the reaction is too slow or impossible without the presence of pectinase. At the beginning of the reaction, all the active-sites are available for substrates and the concentration of substrate is also at its maximum point. So a lot of enzyme-substrate complexes are formed and most products are produced. This is indicated by the slope of the graph. The graph at the beginning of the reaction is almost straight line (from minute 0 to minute 2) which shows the rate of reaction increases constantly. The gradient of the graph decreases two minutes after the initial reaction. This can be seen from the graph as the graph starts to flatten off. From minute 2 to minute 8, more and more substrate molecules are converted into products. Less substrate is available for active-sites. Not all enzymes area occupied with substrate which in turn leads to the less yield of product. We expect the graph to flatten off after 8 minutes. But this reaction could not give this shape because it needs a longer time for the experiment. ...read more.


Taking the average also minimises the uncertainty and inaccuracy. The experiment was not repeated either. By repeating the experiment, we can take average result for individual test and thus can obtain a more reliable result. Besides all these limitations, the apple juice sauce we used was already cooked. We did not know which part of apple contained in the sauce. For example, thicker tissue will take longer to be broken down while thinner tissue will take shorter time. This in turn might give us different volume of apple juice per unit time. We also did not know the type of apple used. Different types of apple might give us different yields due different types of tissues which might need different conditions for enzymes to work on. Conclusion The reliability and the precision of the result is lower in this experiment. Other possible coursework 1. The effect of different temperatures on the activity of enzymes to find out the best economic condition for the industry 2. The effect of different pH on the activity of enzymes to find out the best economic condition for the industry 3. The effect of different concentrations on the activity of enzymes to find out the best economic condition for the industry 4. The effect of enzymes on cooked and uncooked apple sauce to find out which gives the most yield 5. The effect of enzymes on different types of apples to find out which gives the most yield 6. The effect of enzymes on ripe and unripe apples to find out which gives the most yield ?? ?? ?? ?? 11 ...read more.

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