decay

decay in milk

bacteria in milk use enzymes to produce acidic molecules

Using a pipette, measure 5cm³ lipase solution in test tube so…

you can control when recation starts.

In another test tube, add 5 drops of Crecol Red (indicator) so…

you can see the pH change later.

Add 5cm³ and 7cm³ sodium carbonate to milk test tube (solution should be purple) so …

you see the colour change.

Place thermometer into milk test tube so…

you can monitor the temperature.

Place both test tubes into a water bath of the first temperature so…

you can control the starting temperature.

Wait until temperature of solutions matches water bath so…

you can start at the correct temperature.

Using a pipette, transfer 1cm³ lipase to milk test tube and stir to…

start the reaction.

At the same time, start a timer to…

measure how fast the colour changes.

Digestion of fat by lipase releases…

fatty acid.

Stop timing once solution turns yellow as…

the solution is now acidic.

Record results so…

you can compare to other temperatures.

Repeat at other temperatures so…

you can observe the effect of temperature on decay.

Use a clean test tube for each temperature because…

left over lipase will trigger the reaction before we are ready.