Practical / Laboratory Work and Project
Laboratory work
The practical paper tests safe bench practice, standard methods, accurate recording and interpretation. Learn the principle, apparatus, procedure and calculation for each determination.
- Moisture: oven drying at 105°C to constant weight; cool in a desiccator before weighing.
- Ash: muffle furnace at about 550°C; represents mineral residue.
- Fat: Soxhlet extraction with petroleum ether.
- Protein: Kjeldahl digestion, distillation and titration; crude protein = nitrogen × 6.25.
- Acidity: titration with standard alkali; express as % citric acid or lactic acid as specified.
- Total soluble solids: refractometer, °Brix; correct for temperature.
- Sensory: clean booths, coded samples, 9-point hedonic scale, panelists screened and not biased.
- Microbiology: total plate count, coliform count, yeast and mould count under aseptic conditions.
Project work
A project report should state the title, objectives, background, methodology, results, discussion, conclusion and references. Keep raw data, calculations and photographs of the process. A common project is formulation and shelf-life study of a local product.
Worked example
An empty moisture dish weighs 20.000 g. With a 5.000 g sample it weighs 25.000 g. After drying and cooling it weighs 24.750 g. Moisture = (25.000 − 24.750) ÷ 5.000 × 100 = 0.250 ÷ 5.000 × 100 = 5.0%. The reasoning subtracts the dried mass from the initial dish-plus-sample mass to get water lost, then divides by the sample mass.
Traps
Weighing hot dishes gives false low moisture. Skipping duplicates reduces reliability. Using the wrong acid factor changes acidity results. In sensory tests, do not discuss samples. Record units and significant figures correctly.