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Determining the effect of changing the concentration of calcium ions on the rate of coagulation of milk

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Determining the effect of changing the concentration of calcium ions on the rate of coagulation of milk Coagulation is essentially the formation of a gel by destabilizing the casein micelles causing them to aggregate and form a network which partially immobilizes the water and traps the fat globules in the newly formed matrix. This may be accomplished with enzymes. * Ref 1 Rennin is an enzyme produced in the stomach of mammals, particularly young ones, to curdle milk, preventing the rapid flow through the digestive system without time for digesting the available proteins. The casein proteins found in milk are the substrate. This will be the enzyme used to coagulate milk in my experiment. Calcium activates rennin through allosteric regulation; the active site of rennin is not naturally specific to the shape of the substrate in milk, but with Calcium as an allosteric activator, the active site is altered to the correct shape. This allows the reaction to be catalysed. Prediction I predict that as the concentration of calcium ions increase, the rate of coagulation will also increase. ...read more.


In doing so, I can fully control the concentration of calcium ions present in the milk, by adding the afterwards in the form of Calcium Chloride, a 1.0 mol dm-3 solution. I will dilute the CaCl2 with distilled water to achieve the desired concentration of calcium ions. By measuring the time taken for coagulation to begin, I can work out the rate and determine which concentration of calcium ions gives the fastest rate. When I add the sodium citrate, I will shake well and leave for 10 minutes to allow for all the calcium ions to be taken up, forming the insoluble precipitate calcium citrate; this can be filtered out and removed from the solution, but as the calcium ions are no longer available to the enzyme, it isn't necessary. I will also include a reaction between the milk, devoid of calcium ions, and the rennin with distilled water instead of calcium chloride; essentially, this is my control. Precision By repeating the experiment, I can produce average results and avoid anomalies. ...read more.


Test tube F - 0 cm3 of CaCl2, 10 cm3 of water. 5. Place the milk, enzyme and CaCl2 solutions into a water bath at 20�C and allow all solutions to reach that temperature. 6. Using a graduated pipette, add 2 ml of milk, 2 ml of rennin and 2 ml of CaCl2 from test tube A to a clean test tube. Shake well and start the timer. 7. Every 5 seconds, use the pipette to take one drop and place it on a microscope slide to check for curd flecks. When they appear, stop the timer. 8. Follow stages 1-4 for each CaCl2 solution. 9. Repeat 4 times. I would record the results gained in the table displayed below, and they can also be plotted in a graph to show the correlation; I have included my estimation of the graph, showing the increase in rate, as the concentration of calcium ions increases. CaCl2 concentration (mol dm-3) Test Tube Time Taken for first flecks to appear (s) Average Time Taken (s) Average rate (s-1) First run Repeat 1 Repeat 2 Repeat 3 Repeat 4 1.0 A 0.8 B 0.6 C 0.4 D 0. ...read more.

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