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Affect of concentration of calcium ions on the coagulation of milk

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Affect of concentration of calcium ions on the coagulation of milk Introduction Milk contains proteins, the majority of which being caseins; there are main types of casein molecules. Three of which readily precipitate with calcium. The fourth type of casein is kappa casein, which does not precipitate with calcium. Kappa casein keeps the other types of casein from coagulating, so the milk remains solublei. The rennin (enzyme) interacts with the kappa casein (substrate), breaking it down into para-kappa-casein (product). Now that the kappa casein has been broken down, the other casein molecules and new para-kappa-casein molecules precipitate with calcium, and milk, fat and some water combines forming a curd.ii Prediction As the concentration of calcium ions is increased, the time taken for flecks of curd to appear will decrease; therefore the rate of the reaction will increase. In this investigation, the rate of the reaction refers to how long it takes for the product to be formed from the enzyme and substrate, and the product to react with calcium. This will happen because if there is a greater concentration of calcium ions, there will be more collisions between the para-kappa-casein, other casein molecules and calcium, meaning the curd will be formed more quickly. ...read more.


By doing this the solution can be easily mixed, and flecks of curd are very easy to observe on the inside of the glass as soon as the solutions are mixed. The water baths will be used and set at a temperature of 40�C as this is around the optimum temperature for the enzyme renniniii, and the milk, rennin solution, calcium chloride solutions and sodium citrate solution will be placed in and allowed to equilibrate to the temperature. The only source of calcium ions needs to be from the calcium chloride, so the concentration will be as accurate as possible. Because there are already calcium ions in the milk, these will need to be removed by using sodium citrate. The volumes of the solutions that will be used each time are as followed. * 10cm3 of milk * 1cm3 of rennin * 1cm3 of sodium citrate solution * 1cm3 of each concentration of calcium chloride solution The procedure for each concentration of calcium chloride will be repeated thee times in order to determine an accurate average value of time. Apparatus I have chosen the following equipment in order to carry out this investigation as accurately as possible. ...read more.


Procedure 1. Measure 10cm3 of the milk from the water bath into a boiling tube, and add 1.0cm3 of the first concentration of calcium chloride and 1.0cm3 of sodium citrate to remove any calcium ions already present in the milk. 2. Using a syringe, add 1.0cm3 of rennin to the boiling tube and immediately start the stopwatch. 3. Swirl the tube to mix the solution, with as much as possible in the water to maintain a constant temperature. As soon as any flecks appear, stop the stopwatch and record the time in a table similar to the one below. 4. Pour the waste solutions into a large beaker for disposal. 5. Repeat steps 1-4 twice more with the same concentration and calculate the average time. 6. Repeat steps 1-5 with each concentration of calcium chloride. Concentration of calcium (mol dm-3) Time taken for flecks to appear (seconds) First run Second run Third run Average 1.0 0.8 0.6 0.4 0.2 0.0 Analysis Upon completion of the experiment, once results have been recorded in the table, they can be plotted on a graph to see if they agree with the prediction. Plot a graph of average time (x-axis) against concentration (y-axis) to see if there is any trend or relationship between time and concentration of calcium ions. ...read more.

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