Peanut flour is made by roasting peanuts, pressing out most of their oil, and grinding the remaining dry cake into a fine powder. The process is straightforward in concept but varies depending on the fat level desired, with commercial peanut flour typically sold at either 12% or 28% fat content.
From Raw Peanuts to Roasted Kernels
Production starts with raw, shelled peanuts that meet food-grade quality standards. In the U.S., these peanuts must comply with federal regulations that limit damaged kernels and minimize contamination from Aspergillus flavus, a fungus that produces aflatoxin, a dangerous carcinogen that can grow on crops in warm, humid conditions.
The peanuts are then dry roasted. Commercial producers use continuous belt roasters with controlled temperature zones, bed depth, and belt speed. A typical roasting cycle runs about 15 minutes at around 175°C (roughly 350°F), though the exact conditions depend on what the manufacturer is after. Light roasts use lower temperatures or shorter times, while dark roasts go further. Roasting serves multiple purposes: it kills harmful bacteria like Salmonella (manufacturers aim for a 5-log reduction, meaning 99.999% of pathogens are destroyed), develops the characteristic peanut flavor, and affects the protein structure of the finished flour.
The roast level matters more than you might expect. Light, medium, and dark roast peanut flours behave differently in recipes. Lower-fat, light-roasted flours thicken liquids more effectively than darker or higher-fat versions, which is useful if you’re using peanut flour as a thickener in sauces or smoothies.
Removing the Oil
Raw peanuts are about 50% fat by weight. To make flour rather than butter, most of that oil needs to come out. There are several ways to do this, and each produces a different product.
Hydraulic pressing is the traditional method. Roasted peanuts are loaded into a hydraulic press, where intense pressure squeezes oil out of the kernels. The length of time the peanuts spend under pressure (called dwell time) determines how much fat remains. This is how most commercial peanut flour at the 12% and 28% fat levels is made.
Screw pressing (also called expeller pressing) works continuously rather than in batches. Peanuts are fed into a horizontal screw press that uses friction and compression to force oil through narrow gaps in a metal cage. Some producers run peanuts through a dry extruder first, which uses shear forces to break open the cell structure and release oil. The extruded material is then immediately screw-pressed before the oil can be reabsorbed. This two-step approach can remove over 90% of the original oil, producing press cakes with roughly 8% fat and 47% protein.
Solvent extraction creates the lowest-fat flours. After initial mechanical pressing, the remaining press cake is washed with a chemical solvent (typically hexane) that dissolves and carries away nearly all residual oil. An additional wash with ethanol can remove bitter flavors and pigments. The solvent is then evaporated off completely. This method strips fat down to just a few percent but can alter the physical and chemical properties of the peanut proteins, unlike purely mechanical methods, which leave the proteins intact.
Grinding Into Flour
After pressing, what remains is a dry, crumbly material called press cake (or peanut cake). This cake is milled into a fine powder using industrial grinders or hammer mills. Commercial peanut flour is typically sieved through an 80-mesh screen, which produces a consistency similar to wheat flour. During this stage, manufacturers monitor the flour for color consistency, fat content, and the presence of any metal particles from the milling equipment.
What Makes Peanut Flour Nutritionally Dense
Removing most of the fat concentrates everything else. A 100-gram serving of defatted peanut flour contains about 52 grams of protein and nearly 16 grams of fiber. That protein density is roughly double what you’d find in the same weight of whole peanuts, because the oil that made up half the kernel’s weight is gone. This is why peanut flour has become popular as a protein boost in smoothies, baked goods, and sauces.
The fat content you choose affects both nutrition and cooking behavior. A 12% fat flour is drier and more absorbent, working well as a thickener or protein supplement. A 28% fat flour retains more peanut richness and flavor, making it better suited for cookies, coatings, and recipes where you want a stronger peanut taste.
Making Peanut Flour at Home
You can make a version of peanut flour in your kitchen, though it will be higher in fat than commercial products since you won’t be pressing oil out. The process is simple: roast raw peanuts at 350°F for about 15 minutes (or use pre-roasted unsalted peanuts), then let them cool completely. Cooling is critical. Warm peanuts will turn into peanut butter the moment you blend them.
Once cooled, add the peanuts to a high-powered blender (which works better than a food processor for achieving a fine texture). Pulse in short 5-second bursts, stopping to scrape the sides and bottom between each pulse. Resist the urge to let the blender run continuously. The friction generates heat, which releases oil from the peanuts and pushes you toward paste territory. Three or four short pulses are usually enough.
Let the finished powder cool to room temperature before sealing it in a container. Stored in the fridge, homemade peanut flour keeps for about three months. Because it retains all of its natural fat, it won’t be as light or absorbent as the defatted commercial version, but it works well as a flavoring in baking, oatmeal, and dressings.