What steps prepare oilseeds for mechanical pressing?

To prepare oilseeds for mechanical pressing, the following sequence of operations is typically performed to liberate the oil from the cellular structures:

• Cleaning: Seeds are passed over magnetic separators to remove any stray metal fragments.12
• Dehulling: If necessary, the shells or hulls are removed from the seeds.12
• Grinding: The remaining kernels or meats are converted into a coarse meal using grooved rollers or specialized hammer mills.12
• Conditioning: Depending on the desired oil quality, the meal may undergo preliminary heating before being fed into hydraulic or screw presses.12

While cold-pressing (without heating) produces virgin oils with fewer impurities, heating the meal prior to pressing increases the oil yield, though it also extracts more nonglyceride impurities.12