Food Analysis - Determination Water and Fat in meat (Dean Stark)
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What are the two layers formed on condensing?
bottom layer water (with .06% toluene) and top layer of toluene (with .05% water dissolved)
What are the relative volumes
18 % water and 82 % toluene
Step 1 - weighing
three 20g samples of minced meat to be analysed - transfer to 3 distillation flasks with 80 mL toluene
When do you stop distillation?
When no water is seen to be coming over
How do you obtain the percentage of the original mass of water?
Transfer water to pre-weighed 200 mL beaker and determine mass
After distillation what happens to the fat and toluene solution?
It is stored for a number of hours
How is the % fat determined?
• 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