Micro-organisms Aim To be able to test milk to see how fresh it is
Context When milk is collected from farms it is then transported in tankers. It is important that the milk collected is fresh or it could contaminate the whole tanker. A farmer needs to ensure that his milk is fresh enough and the Milk Marketing Board can help with this by testing his milk.
Context As milk gets older bacteria grows in it. The bacteria respire using up oxygen and lactose (sugar in milk) turning it into carbon dioxide and lactic acid (makes milk taste sour). Resazurin is a chemical which detects the amount of oxygen present by changing colour. (click here)
Results Bad White Poor Pink to pale pink Fair Mauve to pink Good Blue to mauve Excellent Blue (no colour change) Quality of milk Colour of sample
Method: Testing milk <ul><li>Label test tubes S (sample from farm), F (fresh milk), 1 (1 day old), 2 and 3. </li></ul><ul><li>Using a pipette add 1cm 3 of Resazurin solution to each tube </li></ul><ul><li>Using the measuring cylinder place 5cm 3 of fresh milk in the tube labelled S and put a stopper in it. </li></ul><ul><li>Repeat with the fresh milk in tube F, 1 day old milk in tube 1 etc </li></ul><ul><li>Put all of the test tubes into a rack and place rack into a water bath for 30mins </li></ul><ul><li>Record the colour differences in a suitable table of results </li></ul>
Results table 3 days old (3) 2 days old (2) 1 day old (1) Fresh (F) Sample (S) Test tube Quality of milk Colour of sample
Analysis and Evaluation Aim To be able to explain what our results show and evaluate our experiment.
Analysis My results show that the older the milk…………………… These results happened because ………………… The milk sample taken from the farmer was of ……………………. quality
Evaluation My experiment went… I had problems with … because… To improve my experiment I could… My results would be more reliable if I… I did/did not have odd results………. This was because……………….