Oilseed crops such as canola, soybean, rapeseed, and sunflower oil are large and growing sources of natural seed oil. Mechanical extraction of oil from seeds is a method to get that precious oil out of it.
The seeds from these crops are an excellent source of oil, but there may be challenges in extracting the oil from all of the seeds. Mechanical seed crackers or mills can be used to efficiently crack or break open the seed to expose the oil-rich kernel or endosperm.
The cracked seeds can then be pressed or solvent-extracted to obtain high-quality oils.
Milling is one of the oldest and most effective methods for separating oilseeds from chaff and other plant parts. Milling also helps remove contaminants such as dirt, twigs, leaves, rocks, and other debris that may have fallen into the hopper during loading or transport.
If you are looking for more information about the mechanical extraction of oils from seeds, read further here!
Mechanical Extraction Of Oil From Seeds
There are several methods for extracting oil from seeds. Mechanical extraction is one of the most common methods used in the industry, especially for large-scale production.
As with any manufacturing process, it’s important to understand the limitations of mechanical oil extraction from seed before implementing this method in your own operation.
The oils suitable for mechanical extraction will differ depending on the seed you’re working with. In this post we tried to add the most important information about the different types of equipment and their suitability for mechanical oil extraction, as well as an overview of each step in the process.
As the name suggests, mechanical seed oil extraction is a method that relies on mechanical force instead of chemical processes to extract oils from plant seeds.
The oils are extracted mechanically by breaking the cells in which they are stored and then collecting, filtering, and pressing them. Further, you will find more details on the process of mechanical seed oil extraction and its applications.
What Do Mechanical Seed Crushers Look Like?
A mechanical seed crusher is a rotating drum, roller, or screen that breaks open seeds and removes the chaff or hull. Crushers can be stationary or portable, with or without a conveyor, and can have different sizes, shapes, and designs.
The basic crusher design is a rotating cylindrical drum with openings of different sizes and shapes. The seed hopper feeds seeds into the crusher, where they are ground or crushed between the drum and a stationary anvil.
Mechanical Presses For Mechanical Extraction Of Oil
A mechanical press is a device for compressing seeds and extracting oil by pressing the seeds between two heavy rollers.
The press uses pressure to squeeze the oil out of the seeds, where oil goes into a collecting container, and the so-called press cake is removed. Press designs can vary, but the general principle is to use a heavy roller or set of rollers to apply pressure to the seeds between two heavy plates.
The plates are usually made of stainless steel or hardwood, and they sandwich the seeds between them.
Heavy-duty hydraulic cylinders press the plates together to squeeze the seeds. Press designs can also vary, including single- and double-roller designs or roller-and-plate designs.
The seeds are squeezed between two metal rollers in a single- or double-roller design.
The seeds are sandwiched between a metal roller and a metal plate in a roller-and-plate design.
Double-roller presses work best for seeds with high oil content. The seeds are fed by gravity into the top of the press. The following processing step comes when the press squeezes the seeds to extract the oil.
The press cake is removed from the bottom of the press, and the oil is collected from the top. The oil is often further processed to remove impurities, such as proteins, carbohydrates, and minerals, before being used as the end product.
Solvent Extractors
A solvent extractor is a specialized machine that uses a solvent or an organic liquid that dissolves other substances to extract oil from seeds.
Solvents are often used to extract oils from soybeans, peanuts, and other oilseeds with low oil content. The solvent is heated and mixed with the seeds in a vat or tank.
The solvent breaks down the cell membranes of the seeds, releasing the oil. The solvent and oil mixture is then filtered or separated, and the solvent is recycled or reused.
Due to the high process productivity, solvent extraction is the most widely used method for processing soybeans and peanuts.
Solvent extraction is used primarily to remove oils from low-oil-content seeds that can’t be broken or crushed by a mechanical press.
Rotary disc breakers
A rotary disc breaker crushes seeds by rotating a disc with small notches or serrations that cut the seeds and break open the hull.
Seeds are fed into the machine hopper, and crushed seeds fall through a screen. The screen keeps any large pieces of seeds from falling back into the hopper to be ground again.
As mentioned above, solvent extraction is another common method for extracting oil from oilseeds. The solvent breaks down the cell walls of the seed to release the oil. Then, the solvent is evaporated or removed by heat or pressure. The oil is collected, and the remaining seed cake is used as livestock feed or fertilizer.
Seed shakers or sifters
A seed shaker is a machine or device that shakes or sifts seeds to remove dirt and other unwanted material. This separation process can be done manually by shaking the seeds in a container or using a hand-held device.
Seed shakers are available in many different sizes and styles. They can be hand-cranked or powered by an electric motor. They are often made of stainless steel or other corrosion-resistant materials to help prevent the growth of bacteria or fungi that can grow on moist seeds.
A manual seed shaker usually has a container with an open top and a small perforated screen or sieve near the top. The user scatters the seeds on the screen, then manually shakes the container so the seeds pass through the screen and fall into the bottom of the container.
Alternatives to mechanical extraction of oil from seeds
There are alternatives to mechanical seed crushing or pressing if you have seeds that are too hard or difficult to crack open.
For example, oilseed can be solvent-extracted or extracted with a chemical solvent that dissolves the oil from the seeds, leaving the rest of the material behind.
Another alternative is to use a solvent-assisted extraction process, which combines mechanical crushing and solvent extraction. In this process, the seeds are first crushed to release the oil, and the solvent is then added to the crushed seeds to extract the oil more quickly.
Mechanical crushing is challenging for some seed types, but others, like sunflower seeds, are easy to break open and can be crushed with a roller or press.
Conclusion
Mechanical seed crushing or pressing releases the oil from the seeds and produces an oilcake remaining after the oil has been removed.
On the other hand, solvent extraction is often used with low-oil-content seeds, such as canola, sunflower, or peanuts, that can’t be mechanically extracted.
You can use combined mechanical, and solvent extraction processes when seeds are hard to crush, like flax seeds, or they have high moisture content, like corn kernels.
