Why Roast Oilseeds Before Pressing
In a hot-press oil mill, roasting is not an optional extra — it is the step that conditions the seed so the press can do its job. Heating and mixing the seed before pressing delivers four things:
- Higher oil yield — heat ruptures the cell walls and lowers the oil's viscosity, so more oil releases under pressure and less stays locked in the cake.
- Characteristic aroma & flavour — roasting develops the flavour that defines peanut, sesame and specialty oils. This is essential for premium aromatic oils.
- Better pressing efficiency — conditioned seed flows and presses more easily, lowering energy use and wear on the press.
- Consistent quality — controlled, even roasting gives repeatable results batch after batch.
Illustrative process video: how sesame oil is made, including the roasting step before pressing.
Roasting Temperature & Time by Seed
The right roasting temperature depends on the seed and whether you want a refined or an aromatic oil. As a practical starting point for oil-mill roasting:
| Oilseed | Roasting Temperature | Added Moisture | Note |
|---|---|---|---|
| Peanut / Groundnut | ~130 °C | 3–5% | Develops classic peanut-oil aroma |
| Rapeseed / Canola | ~130 °C | 3–5% | — |
| Sunflower | ~120 °C | 4–6% | Lower temp, oil-rich kernel |
| Soybean | ~140 °C | 2–3% | — |
| Flaxseed / Linseed | ~145 °C | 0% | Roast dry |
| Sesame | 160–220 °C | — | Higher heat for aromatic sesame oil & tahini |
Engineering note: Thermal-oil heated roasters carry oil rated to 300 °C; direct-fired roasters reach 250–270 °C; electric/induction material temperature is held up to ~200 °C. Stirring runs at 30–40 rpm and a batch roasts in roughly 20–30 minutes — exact figures vary by seed, moisture and machine.
How the Roasting Step Works
Whether you run a rotary drum or a flat-bottom pan, the conditioning sequence is the same:
- Clean & condition — clean the seed and adjust moisture (typically 2–6% added water by seed).
- Feed — load the seed into the roaster's drum or pan.
- Heat & stir — raise to the target temperature while the blades turn at 30–40 rpm for even heating without scorching.
- Hold — roast ~20–30 minutes until cells rupture and aroma develops.
- Discharge — send the hot, conditioned seed straight to the oil press.
Drum vs Flat-bottom Roasters — Quick Guide
SinoOil builds both structures, with electric, induction, thermal-oil and direct-fired heating:
- Drum roasters — a rotating horizontal drum tumbles the seed for even, continuous roasting; available electric, open-fire, closed-fire and induction.
- Flat-bottom roasters — a stirred flat pan, simple and fuel-efficient; available induction, electric thermal-oil, fired thermal-oil and solid-bottom fire.
See the full range and specifications on the oilseed roaster overview.
Where Roasting Fits the Oil Line
Roasting sits between cleaning and pressing: cleaning → roasting → pressing → filtering → (refining). It is one stage of a complete edible-oil line. If you are planning a mill, see how to start an oil mill and our sesame and peanut oil line solutions.