Food Analysis - Determination Water and Fat in meat (Dean Stark)

Question 1

What are the two layers formed on condensing?

Answer 1

bottom layer water (with .06% toluene) and top layer of toluene (with .05% water dissolved)

Question 2

What are the relative volumes

Answer 2

18 % water and 82 % toluene

Question 3

Step 1 - weighing

Answer 3

three 20g samples of minced meat to be analysed - transfer to 3 distillation flasks with 80 mL toluene

Question 4

When do you stop distillation?

Answer 4

When no water is seen to be coming over

Question 5

How do you obtain the percentage of the original mass of water?

Answer 5

Transfer water to pre-weighed 200 mL beaker and determine mass

Question 6

After distillation what happens to the fat and toluene solution?

Answer 6

It is stored for a number of hours

Question 7

How is the % fat determined?

Answer 7

• Place the contents of each of the toluene meat samples into tared beakers and rinse the original flask with two or three 10 -15 mL of toluene and add to beaker. After each addition shake. Evaporate the toluene solution to dryness on a hotplate and then over a water bath in fume cupboard - reweigh beaker to determine amount of fat