Aim: To investigate the protease activities in different fruit juices
Background info: Fruit such as pineapple, kiwi fruit, papaya and guava contain proteases (in different amounts), which can speed up the breakdown of proteins. As milk-agar plate is a milk protein, so when it is incubated with fruit juices containing proteases, the milk protein will be broken down and clear zones will appear around the wells containing different fruit juices. Thus, the higher the protease activity, the larger the diameter of the clear zones.
Equation:
Control:
One well in the milk-agar plate is filled with distilled water to act as a control to show that the formation of the clear zone is only due to the fruit juices.
Precautions:
1. wash your hand before handling the fruits because your hands contain proteins which may contaminate the fruits and affect the accuracy of the experiment
2. as during the preparation of the experiment, some bacteria may stick on the apparatus so the fruit juices may be contaminated and the protein in the juices may also be digested by the bacteria thus affecting the result. Therefore, it is suggested that all apparatuses used should be well washed and heated with non-luminous Bunsen flame to kill the bacteria contained
3. make sure the fruits are cut in same size so that the fruit juices made are of the same volume to ensure a fair test
4. the temperature for incubating the milk-agar plate should not be too high(around 35℃ or else the protease contained in the juices will denature and no result can be shown
5. do not flood the wells or allow the juices to contaminate the other parts of the milk-agar
Assumptions:
1. the optimum temperature of the protease activities in different fruit juices are the same apparatus and materials: wb
Procedure: wb/ textbk
Independent v: types of fruits that are used to make the fruit juices dependent v: the diameter of the clear