Practical Skills, Laboratory Work and Project Assessment
Domain 10 assesses practical laboratory technique, record keeping and project work. You should be able to describe a test, calculate a result and defend your method in a viva.
Core rules
- Mix the sample, use clean glassware, correct the lactometer to 20°C and read the Gerber butyrometer at the meniscus.
- Platform tests include COB, alcohol, acidity, MBR/resazurin; adulteration tests include iodine for starch and resorcinol for cane sugar.
- Record raw data, units, observations and calculations; a project report needs aim, method, results, discussion and conclusion.
- Follow lab safety: no mouth pipetting, label reagents, dispose of waste correctly. Use a blank and duplicate where possible.
Worked example
Titrate 10 mL milk with 0.1 N NaOH; the endpoint uses phenolphthalein and takes 1.8 mL. % lactic acid = (1.8 × 0.1 × 90 × 100) / (10 × 1000) = 0.162%. The reasoning is that 1 mL of 0.1 N NaOH is equivalent to 0.009 g lactic acid; the result is expressed as g per 100 mL.
Traps
- Not mixing the sample gives a false fat result.
- Reading the wrong part of the meniscus changes the fat value.
- Forgetting the temperature correction changes the lactometer result.
- A copied project without your own data loses marks in viva.