Pretreatment follows a fixed logic: remove what is not seed, remove what is not kernel, then open the kernel up. A typical line runs cleaning → shelling → crushing/flaking → roasting, feeding directly into the screw press. The full equipment chain is covered on our seed preparation equipment hub.
Cleaning comes first because stones, soil, metal and stalks damage downstream machines and contaminate the oil. A seed cleaning machine removes light impurities and dust, while a vibrating screen grades the seed by size and rejects oversize and undersize material before it reaches the sheller.
Shells and hulls contain almost no oil, yet they absorb oil during pressing — so every kilogram of shell that enters the press takes oil out of your cake. Removing hulls with a seed dehulling machine raises practical yield and also protects the screw press from abrasive wear, since hulls grind against the worm shaft and barrel.
Moisture control is the key operating variable. For peanuts, approximately 8–13% kernel moisture is ideal: too dry and breakage rises sharply, too wet and throughput drops. A common winter practice is to spray roughly 10 kg of warm water over 50 kg of peanuts, cover with film for about 10 hours, then sun-dry for about 1 hour before shelling. Well-tuned machines such as a peanut shelling machine typically achieve 95–98% shelling rates with only 2–5% kernel breakage.
Clean, dehulled kernels are then crushed or flaked to increase surface area, and roasted to make the oil extractable. Heat does two things: it denatures the proteins that bind oil inside the cell, and it creates pores in the cell walls through which oil can escape under pressure. Roasting temperatures range from roughly 90°C to 260°C depending on the seed; sesame is typically roasted at around 170°C for about 15 minutes.
The yield impact is dramatic. Published research on sesame found oil yield improved from 33.5% to 62.6% with proper roasting. Drum and flat-bottom roasters in electric, fired and thermal-oil configurations are compared on our seed roasting machine page.
Size each stage to the press behind it: an undersized cleaner or sheller starves the press, while skipping roasting leaves recoverable oil in the cake. Start from the seed preparation equipment range and work backwards from your target capacity. SinoOil Machinery has supplied factory-direct, ISO9001/CE-certified pretreatment and pressing equipment to mills in 80+ countries since 2009 — contact our engineers for a line layout matched to your seed type and capacity.
Yes. Even a single-press mill benefits from cleaning and shelling: shells absorb oil during pressing and accelerate screw press wear, while unremoved stones can damage the press outright. Roasting then typically adds the largest single yield gain of any pretreatment step.
Approximately 8–13% is ideal. Too dry causes high kernel breakage; too wet reduces shelling efficiency. In dry winter conditions, spraying about 10 kg of warm water per 50 kg of peanuts, covering for around 10 hours, then sunning for about 1 hour restores workable moisture.
Heat denatures the proteins that hold oil inside seed cells and creates pores in the cell walls, letting oil flow out under press pressure. Research on sesame recorded yield improving from 33.5% to 62.6% after roasting.
Cleaning and screening first, then dehulling or shelling, then crushing or flaking, then roasting, then pressing. Cleaning protects all downstream machines, and roasting is done last so the heated, conditioned material goes straight into the press.
SinoOil engineers size the right pretreatment equipment for your capacity — free plant design included.
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