An investigation to find out what the effect of changing the concentration of calcium ions has on the rate of coagulation of milk

Authors Avatar

                                                         

An investigation to find out what the effect of changing the concentration of calcium ions has on the rate of coagulation of milk

Introduction: I am going to find out what the effect of changing the concentration of calcium ions, using calcium chloride has on the rate of the coagulation of milk.

Background: Milk contains 290mg of calcium in every 8 ounces of milk. The function of calcium is that it helps maintain and build strong bones and teeth. However when the enzyme rennin is used on it, it can cause the milk to coagulate (clot). This process can be used to make cottage cheese as the rennin helps separate the curds from the milk

Rennin is an enzyme which is used in the coagulation of milk. It can be used to catalyse the conversion of a protein called casein, which is found in the milk. This is converted into para-casein by removing a glycopeptides from the casein. The para – casein further coagulates in the presence of the calcium ions to form white curds. This can then be separated from the whey to make cottage cheese. However in the experiment which I am carrying out, when the milk starts to coagulate flecks are first formed.¹

¹                                         200

Prediction: My prediction is that when the concentration of calcium ions in calcium chloride is increased, then the rate of coagulation of milk will also increase. This is because there are more Calcium ions which can coagulate the para – casein forming flecks.

The graph of the experiment should look something like this:

Preliminary experiments: I carried out two preliminary experiments to see what the right conditions for the experiment should be.

My first experiment was to see what the right volume of rennin was. I decided to use 1cm³ of sodium citrate to first remove all the calcium ions from the 10cm³ of milk. The pH which I used was neutral as, although the ideal pH is about 3, I decided that it would have coagulated straight away if I had done this and it would have made the experiment less accurate if I had changed it. For my first experiment I kept it at room temperature, which was 26ºC, when measured with a thermometer. I then used two different volumes of rennin. For the calcium chloride I used concentrations of 1, 0.8, 0.6, 0.4, 0.2 moldm³

Join now!

These results and the graph showed me that when there is an increase in the volume of rennin, the time taken for the milk to coagulate decreases. This is because of an increase in enzyme concentration, which means that there is more chance of enzyme substrate complexes forming, and so more of the casein in the milk is catalysed. Also the greater the concentration of calcium chloride, the less time it takes for the milk to coagulate. However, although the time taken decreases, I am going to use 1cm³ of rennin as this means that when the ...

This is a preview of the whole essay