Cereal, Pulse and Oilseed Processing
Cereal, pulse and oilseed processing converts grains and seeds into milled fractions, edible pulses and oils. The exam tests milling principles, parboiling, milling yields, pulse dehusking, oil extraction and refining, rancidity and antinutritional factors.
Core rules
- Rice milling removes husk, bran and germ. Parboiling hydrates paddy, gelatinizes starch and improves milling recovery and nutrient retention.
- Wheat roller milling separates bran, germ and endosperm; reduction rolls reduce particle size. Flour extraction rate affects ash and colour.
- Pulse milling involves conditioning, dehusking and splitting. Cotyledon breakage and losses reduce dal yield.
- Oil extraction uses mechanical pressing (expeller) or solvent extraction, commonly with hexane. Crude oil is refined by degumming, neutralization, bleaching and deodorization.
- Free fatty acids indicate oil hydrolysis; peroxide value indicates oxidative rancidity. Lipase and lipoxygenase promote deterioration.
- Antinutritional factors such as trypsin inhibitors and phytates are reduced by soaking, germination, heating or fermentation.
Worked example
1000 kg paddy gives 200 kg husk, 100 kg bran and 20 kg process losses. Polished rice = 1000 − 200 − 100 − 20 = 680 kg. Milling yield = 680 ÷ 1000 × 100 = 68%. The reasoning subtracts each separated stream from the original paddy mass.
Traps
- Confusing parboiling with cooking.
- Reporting milling yield on a changed basis.
- Ignoring hexane recovery in solvent extraction.
- Using peroxide value to measure hydrolysis instead of oxidation.
- Forgetting that milling removes nutrients.