Soybean meal is made by crushing soybeans, removing most of the oil, and then heat-treating the remaining material to create a high-protein product. The finished meal typically contains 48 to 56% protein, making it one of the most protein-dense plant-based ingredients available for animal feed and food manufacturing. The exact process varies depending on scale and equipment, but every method follows the same basic sequence: prepare the beans, extract the oil, remove the solvent or moisture, and apply heat to make the protein safe and digestible.
Cleaning and Preparing the Beans
Before any oil can be removed, whole soybeans need to be cleaned, cracked, and conditioned. The beans are first run through screens and magnets to remove dirt, stones, and metal debris. They’re then cracked into several pieces using roller mills, which breaks each bean into roughly six to eight fragments and loosens the outer hull.
At this stage, many processors remove the hulls entirely. This step, called dehulling, is what separates higher-protein meal from standard meal. The hull is mostly fiber and contributes very little protein. Removing it concentrates the protein found in the inner cotyledon, pushing the final meal closer to 49% protein or above. Leaving the hulls in produces a lower-grade meal with more fiber and less protein per pound.
The cracked, dehulled pieces are then conditioned by heating them to 60 to 90°C at a moisture level of 9 to 12%. This softens the soybean fragments so they can be flattened into thin flakes without crumbling apart. Flaking is critical: the thinner and more uniform the flakes, the more efficiently oil can be washed out in the next step. Processors aim for consistently thin flakes because thick or uneven pieces trap oil inside and reduce yield. Generating too many fine crumbles during cracking or flaking also causes problems downstream, so handling at every stage is kept as gentle as possible.
Removing the Oil: Two Main Methods
Oil extraction is the heart of soybean meal production. There are two primary approaches, and the one you use determines the fat content, cost, and protein quality of your final meal.
Solvent Extraction
This is the dominant method worldwide. Soybean flakes are washed with hexane, a petroleum-derived solvent that dissolves vegetable oil on contact. Hexane is selective: it pulls the oil out of the flakes while leaving proteins, sugars, and fiber largely undisturbed. The solvent travels into each flake, softens and dissolves the oil, and the resulting mixture (called miscella) flows back out and is washed away by fresh solvent.
Solvent extraction is extremely efficient. It removes all but about 0.5% of the oil from the flakes, leaving a very lean, high-protein meal. The oil-solvent mixture is then separated by evaporation, with the hexane recovered and recycled back into the system. The spent flakes, still saturated with solvent, move into a piece of equipment called a desolventizer-toaster, where steam drives off the remaining hexane and simultaneously heats the meal. Uniform flow into this machine matters: surges or uneven feeding lead to inconsistent cooking and wasted energy.
Mechanical Expelling
In mechanical processing, soybeans are pushed through an extruder that uses intense friction and pressure to squeeze oil out of the material. The friction alone generates temperatures above 130°C, which is hot enough to break open the oil-containing structures inside the bean without needing a separate cooking step. The extruded material is then pressed in an expeller to force out additional oil.
This method is simpler and avoids chemical solvents entirely, which makes it appealing for organic or specialty feed markets. The tradeoff is efficiency. Mechanical expelling leaves significantly more oil in the meal compared to solvent extraction, and it costs roughly twice as much per unit of oil produced (about $3.04 per kilogram of oil versus $1.60 for solvent extraction at similar plant sizes). Multiple passes through the press can recover more oil, but repeated pressing generates excessive heat that darkens and degrades the oil quality. For these reasons, mechanically expelled meal is typically used in targeted livestock feed applications where the higher residual fat content is actually desirable.
Heat Treatment and Safety
Raw soybeans contain compounds called trypsin inhibitors that interfere with protein digestion in animals and humans. If soybean meal isn’t properly heat-treated, these compounds remain active and dramatically reduce the nutritional value of the protein. Industrial soybean meal is steam-treated at 110 to 130°C to denature these inhibitors and bring their activity down to safe levels.
The temperature required depends on the soybean variety. Research published in Foods found that heating conventional soybean varieties to 100°C for 10 minutes reduced the primary trypsin inhibitor from 4.17 mg/g to 0.60 mg/g, but reaching levels comparable to a fully safe meal required temperatures of 121°C. Low-inhibitor soybean varieties responded much more dramatically to heat: the same 10 minutes at 100°C dropped inhibitor levels from 1.48 mg/g all the way to 0.03 mg/g, with protein digestibility reaching 81.4%.
Getting the heat treatment right is a balancing act. Too little heat leaves active inhibitors that reduce protein digestion. Too much heat damages the protein itself, particularly the amino acid lysine, which becomes chemically locked up and unavailable to the animal eating the meal. The sweet spot is a narrow window where inhibitors are deactivated but protein quality is preserved.
How Processors Test for Quality
Two lab tests are standard in the industry for checking whether soybean meal was heated correctly.
The urease test measures the activity of an enzyme that, like trypsin inhibitors, is destroyed by heat. A urease reading above 0.15 pH units suggests the meal was underprocessed and likely still contains active inhibitors. A reading below 0.05 indicates the meal was overcooked, which means protein damage is likely. Older animals, particularly laying hens, can tolerate higher urease values (up to 0.25 or beyond) because they’re less sensitive to residual inhibitors.
Protein solubility in potassium hydroxide (KOH) is the second key measure. This test checks how much of the meal’s protein can still dissolve, which reflects how available it is for digestion. Optimally processed meal falls in the 78 to 84% solubility range. Values between 84 and 89% may indicate slightly underprocessed meal, though it’s generally acceptable for mature birds. Values below 74% signal serious heat damage and reduced lysine availability for all animals.
What the Final Product Looks Like
Finished soybean meal is a dry, crumbly, tan-colored material with a mild toasted smell. Its nutritional profile varies depending on whether hulls were removed and how the oil was extracted. Dehulled, solvent-extracted meal typically runs 48 to 56% crude protein, with residual fat between 0.8 and 2.3% and total dietary fiber of 17 to 21%. Mechanically expelled meal has higher fat content (sometimes up to 9%) because the pressing process is less thorough at removing oil.
The protein in soybean meal is what makes it so valuable. It has a strong amino acid profile, particularly in lysine, which is the first limiting amino acid in most grain-based animal diets. This is why soybean meal dominates as a feed ingredient for poultry, swine, and aquaculture worldwide.
Small-Scale and Farm-Level Production
If you’re looking to produce soybean meal on a small or farm scale, the mechanical route is the practical choice. Solvent extraction requires specialized, enclosed equipment to handle hexane safely, along with solvent recovery systems that are expensive and heavily regulated. That rules it out for most operations outside of commercial crushing plants.
A basic small-scale setup involves an extruder and a screw press (expeller). The extruder heats and ruptures the beans through friction, and the expeller squeezes out the oil. You’ll also need a way to dry and cool the meal after pressing, since hot, moist meal will spoil quickly. Rotary dryers and simple cooling systems serve this purpose. Cracking and flaking equipment can improve your oil yield, but some small operators skip the flaking step and rely on the extruder to do the cell disruption work.
The key challenge at small scale is achieving adequate heat treatment. Without a steam-jacketed desolventizer-toaster, you’re relying on the heat generated during extrusion (which does exceed 130°C) to deactivate trypsin inhibitors. For most soybean varieties, this is sufficient, but testing the finished meal with a urease kit is the only way to confirm the inhibitors have been adequately reduced. These test kits are inexpensive and widely available through feed-testing suppliers.