Post-Harvest Technology and Storage
What the domain tests
Post-Harvest Technology and Storage tests maturity, harvesting, threshing, cleaning, grading, drying, packaging, storage and loss prevention. Expect moisture and weight-change calculations.
Core rules
- Harvest at proper maturity; delay causes shattering, sprouting and quality loss.
- Threshing separates grain from chaff; cleaning removes foreign matter; grading sorts produce by size, colour and quality.
- Safe storage moisture differs by produce: cereals generally around 12-13%, pulses lower, oilseeds lower still. High moisture leads to heating, mould and insects.
- Storage structures should be dry, ventilated, rodent-proof and clean. Fumigation controls storage insects but requires trained handling.
- Cool-chain management is essential for fruits, vegetables and flowers.
- Value addition - cleaning, grading, packaging, processing - reduces losses and raises income.
Worked example
1000 kg of grain at 20% moisture is dried to 14% moisture. Dry matter = 1000 x 0.80 = 800 kg. At 14% moisture, dry matter is 86% of final weight. Final weight = 800/0.86 = 930.2 kg. Reasoning: dry matter does not disappear during drying; only water is removed. The loss in weight is water, not grain.
Traps
Do not use relative humidity as a substitute for grain moisture. Do not store freshly harvested grain without drying. Do not confuse cleaning with grading. Do not mix old and new stock. Fumigation is not a substitute for hygiene.