Practical Skills and Project Work
This domain tests laboratory and project skills: measurement, sensory evaluation, microbial testing, record keeping, safety and report writing. Expect questions on procedures, calculations and interpretation.
Core concepts
- Analytical tests: moisture by oven drying; TSS by refractometer; acidity by titration; pH by calibrated meter; microbial count by plate count.
- Sensory evaluation: trained or consumer panels, coded samples, controlled lighting and temperature, and a defined scale such as a 9-point hedonic scale.
- Project report: title, objectives, materials, methods, observations, results, discussion, conclusion and references.
- Safety: lab coat, goggles, safe handling of glassware, chemicals and heat; correct waste disposal.
Worked example
A 10 mL juice sample is titrated with 0.1 N NaOH and uses 8.5 mL. Acidity as citric acid = (8.5 × 0.1 × 64) ÷ (10 × 10) = 0.544%. The factor 64 is the equivalent weight of citric acid in mg per meq; dividing by sample volume and 10 converts to percentage. A result of 0.544% should be compared with the product standard, not judged in isolation.
Traps
Using unstandardised NaOH; forgetting to calibrate the pH meter or refractometer; testing samples at different temperatures; poor sensory panel instructions; omitting raw data and calculations from the project report.