Processing of Cereals, Pulses and Oilseeds
6. Processing of Cereals, Pulses and Oilseeds
This domain tests the milling, polishing, extraction and refining of staple crops, with emphasis on yield, nutrient loss and quality. Punjab’s wheat-rice system makes this a high-scoring area.
Core rules
- Wheat milling: cleaning, conditioning/tempering, break rolls, reduction rolls, sifting and blending. Flour extraction is commonly 72–75%; more extraction darkens flour and increases ash.
- Rice milling: paddy → cleaning → dehusking → polishing → grading. Parboiling (soaking, steaming, drying) improves milling yield, gelatinises starch and moves vitamins into the grain.
- Pulse milling: conditioning, dehusking and splitting; losses occur as brokens and powder. Pretreatment with oil/water improves dal recovery.
- Oilseeds: cleaning, dehulling, size reduction, cooking, pressing (ghani/expeller) or solvent extraction, then refining (degumming, neutralisation, bleaching, deodorisation).
- Anti-nutritional factors in pulses and oilseeds (trypsin inhibitors, phytates) are reduced by soaking, germination, cooking or heat processing.
Worked example
Milled rice yield from 100 kg paddy: husk 20 kg, bran 8 kg, brokens 2 kg, foreign matter 1 kg. Head rice = 100 − (20 + 8 + 2 + 1) = 69 kg, i.e. 69%. Reasoning: account for every stream; head rice excludes brokens, so do not count brokens as head rice.
Traps
Parboiling is not the same as boiling rice for eating. Higher flour extraction is not always better; ash and colour increase. Solvent extraction is not the same as expeller pressing. Aflatoxin risk in oilseeds and cereals must be controlled by storage moisture.