1.1 How temperature affects the rate of milk hydrolysis

Question 1

What is casein?

Answer 1

A milk protein which makes milk white and opaque
When casein is digested the milk becomes clear

Question 2

What is the method?

Answer 2

1. Using a glass rod, stir milk to ensure the milk powder has dissolved
2. Add 10cm^3 of milk to a 50cm^3 beaker with a 10cm^3 syringe
3. Add 1cm^3 of pH buffer to beaker and stir with a glass rod
4. Place beaker in water bath for 5 minutes for the milk to reach the correct temperature
5. After 5 mins, before removing from water bath, add 1cm^3 of enzyme (protease) and start stop watch at the same time
6. Place your beaker of milk on a laminated cross on your desk
7. Record the exact time the cross could be first seen
8. Rinse equipment and repeat with the other water bath temperatures

Question 3

What is the risk of using an enzyme and what is the control measure?

Answer 3

Risk - enzymes can irritate the eyes/skin
control measure - wear eye protection and lab coats, wash off the skin with soap and plenty of water, wipe up the solution spills with a damp paper towel

Question 4

What is the risk of using a water bath and what is the control measure?

Answer 4

Risk- hot water can scale skin
Control measure- use tongs when removing test tubes from water bath, if scalded run under cold water and seek first aid immediately

Question 5

What is the risk of using glassware and what is the control measure?

Answer 5

Risk- if glass smashes you could cut yourself
Control measure- keep all glassware in the centre of the desk at all times and place test tubes in a test tube rack, if injured seek first aid immediately

Question 6

Describe the limitations of this procedure and the improvements you would carry out to give more valid/ reliable data

Answer 6

1. The different test tubes were left in the water bath for different times - to improve only out a test tube in when finished with one to take out at same time
2. The temperature decreased when taking the test tube out of the water bath to the station - to improve, work straight away next to the water bath
3. Lid of the water bath was constantly taken on and off so water may not of been at required temperature - to improve only remove lid when removing or inserting test tubes and place back on quickly

Question 7

Give 2 control variables

Answer 7

1. Concentration of substrate
2. pH - used a buffer to keep it consistent