A Pressing Matter: How to Make Oil from Seeds and Nuts
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A Pressing Matter: How to Make Oil from Seeds and Nuts

Jul 08, 2023

Learn how to make oil from seeds right at home! Bevin Cohen shares sunflower oil, pumpkin oil, peanut oil, and walnut oil benefits as well as how to process and store them for the best oil possible.

Plant-based oils, extracted from seeds, nuts, and occasionally fruits, have been a fundamental part of the human diet since as early as 6000 BCE. Archaeologists uncovered evidence of olive oil production in northern Israel ruins believed to be around 8,000 years old; in North America, archaeologists from Indiana University have found evidence of hickory nut oil extraction in the remnants of an ancient kitchen presumed to be more than 4,000 years old. These oils were vital to the health and well-being of their producers. The dietary fats found in seed and nut oils play a fundamental role in the body, assisting with the proper absorption of vitamins and with essential brain and nerve function.

In the 8,000 years since the first olive was squeezed to release its flavorful, golden essence, the use of oils in food, medicine, and religious ceremony hasn't undergone many notable changes, but production methods have evolved dramatically. The earliest technique was the "wet extraction method." In this method, the seeds or nuts are hulled, crushed, added to water, and then boiled. Oils float to the surface, where they’re skimmed off and reserved. This is a slow and low-yielding process. The first mechanical press was developed in India around 2000 BCE for the extraction of sesame seed oil. This early machine, called a ghani, resembled a large mortar and pestle and was typically powered by oxen; modern motor-powered models are still commercially available today, used most commonly across the Indian subcontinent.

A variation of this technology, still reliant on applying direct pressure to the oilseed, is an "expeller press." This machine is composed of a rotating turnscrew, housed within a horizontal cylinder, that gradually increases pressure on the seed or nut when turned. These expeller presses can be manually operated or motorized. I recommend them for the home-scale oil presser; they’re widely available in motorized or manual, easy to operate, and highly efficient.

With the diverse selection of seed and nut oils available at the local grocery store, why should someone put the time and effort into pressing their own? The foremost reason is flavor. Since oils are essentially fats, they break down and go rancid over time. Unlike mechanically extracted oils, most commercial oils are solvent-extracted using hexane. This chemical oil extraction method is high-yielding and profitable, but these oils are heavily refined, bleached, deodorized, and degummed. The resulting oils have an incredibly long shelf life, but they lack flavor, color, and aroma. While convenient, refined oils don't offer the same qualities that small-scale, cold-pressed oils do.

With the proper equipment, growing, foraging, and pressing high-quality oils right at home is easy and rewarding. Here are some of my favorite oilseed crops to help you get started.

Brilliant, golden oilseed sunflowers are an easy-to-grow annual crop, and the small, black-shelled seeds yield 24% to 47% oil. These are the same sunflower seeds that are also sold as birdseed. While many hybridized sunflowers exist on the market today, including ones bred specifically for oil production, even the most common varieties will produce a flavorful and useful oil. As their name suggests, they grow best in full sun. They prefer loose, well-drained soil and should be planted after danger of frost has passed.

Allow your sunflowers to mature in the field until their foliage begins to yellow and the backs of the flower heads turn brownish-yellow. Cut the stalks about 6 inches below the flower and toss the heads into a basket. Easily remove the seeds by rubbing them loose by hand or over hardware cloth, allowing the seeds to collect in a container. Sift the seeds through screens, or winnow using a box fan, to remove any debris. Allow your seeds to dry for 7 to 10 days, and then they’ll be ready to be pressed or stored in airtight buckets until pressing time.

Run the seeds through the press whole, in-shell, or crushed. The resulting oil will be a deep golden color with mild, nutty flavor, excellent for oil- and vinegar-based salad dressings and marinades. It's also high in vitamin E and can be used topically, which makes it valuable for use in skin-care products.

The typical orange field pumpkin is one of many cultivars of the species Cucurbita pepo. This species includes most summer squashes as well as a few winter-type squashes — which, as their name implies, are most commonly stored for use in winter. The cucurbit family also includes other species of domesticated squash, such as C. maxima and C. moschata, and the seeds from any of these species are considered edible and can be pressed for their oil, although some varietals of C. pepo have been developed specifically for use as oilseed crops.

People first pressed pumpkins for their oils in central and eastern Europe. Around 1870, a Styrian pumpkin farmer in southeast Austria discovered a random genetic mutation that resulted in a crop of pumpkins that produced hulless seeds. These seeds proved to be ideal for oil extraction, and the resulting oil was considered superior in flavor and quality. Since that day, a number of hulless seeded pumpkins have been developed, all of which are ideal for roasting, snacking, and oil production. If these unique varieties are unavailable to you, don't worry. Any pumpkin or squash seeds can be pressed with their shells, and the oil pressed from butternut squash (C. moschata) is robust and flavorful, especially if you lightly toast the seeds before pressing.

Collecting a significant quantity of pumpkin seeds from your garden by hand can be laborious. Larger-scale farmers use specialized tractor-pulled seed-extraction machines. Consider renting this machinery if you plan to extract more than sample-sized quantities of pumpkin seed oil.

Lightly toast the seeds before running them through your press. The deep-reddish-green oil is a flavorful delicacy. The oil has a low smoke point and shouldn't be used for high-heat applications, but it's perfect for cold culinary uses, such as salad dressings. Try it drizzled on avocado!

Native to South America, peanut cultivation was well-established across the continent in pre-Columbian times. Spaniards took peanuts with them back to Europe, where they were well-received and quickly circulated. Enslaved Africans then brought these legumes to North America in the mid-to-late 1600s, but peanuts remained a small-scale garden crop until the 1930s. Thanks to agricultural scientist George Washington Carver, who developed hundreds of uses for the crop, peanuts have become a commercial mainstay around the world.

Peanuts grow best in a long, warm season and need 120 to 150 days to mature. They prefer sandy soil and need full sun for best production. When leaves and stems turn yellow and die back, use a garden spade or fork to loosen the soil, and then remove the plants from the ground. Move the plants to a sheltered area for drying. After 2 to 3 weeks, once the hulls are completely dry, remove the peanuts from the plants.

Before running through the oil press, remove the peanuts from their shells. For small batches, hand-shelling is reasonable, but for anything more than that, alternative shelling methods may be necessary. Simply crush the shells using a rolling pin, food processor, or similar tool, and add the peanut-shell debris to a bucket of cold water. The lighter shell particles will float, while the heavier peanuts will sink to the bottom. The peanuts can then be dried in a low-temperature oven.

Roasting the peanuts before pressing will result in an oil with a deep, nutty flavor and dark, golden-brown color. To increase yields, break toasted or raw peanuts into smaller pieces before pressing. Roasted peanut seed oil is typically enjoyed as a flavoring oil, similar to how toasted sesame oil might be used, while oil pressed from raw peanuts is excellent for frying.

Most commercially available walnut oil is pressed from the domesticated English walnut, Juglans regia. Thought to have originated in Iran, English walnuts are now cultivated around the world. North America is also home to a number of native walnut species, most notably the black walnut, J. nigra. All walnut species produce an edible kernel, but some have thick shells and smaller seeds.

Growing walnuts from seed can be a long process, taking up to 10 years from seed until nut harvest. The abundance of wild black walnut trees across North America, or already established groves of English walnuts, can provide plenty of walnuts for all oil needs. Foraging for wild nuts is an alternative, although the English walnut is the easiest to work with, because the hull splits open upon maturity, unlike the black walnut, whose hull remains intact even after ripening and dropping from the tree.

The walnuts will then need to be washed and the shells removed. You can remove a walnut hull many ways, but I’ve found it's easiest to use a tabletop corn sheller. A simple nutcracker should be all that you need for English walnuts. Black walnuts, on the other hand, will require a hammer or similar tool before tossing them into a bucket of cold water. The lighter shells will float, while the heavier nutmeat will sink to the bottom.

Heating the walnuts before pressing will increase yields. Walnut oil has a golden amber hue and a light, nutty flavor, although roasting the seeds before pressing will result in a slightly darker color and deeper flavor. Walnut oil can be used to sauté and stir-fry, but the delightful flavor also lends itself well to cold-temperature uses.

Regardless of which seed or nut oil you press, the process of filtering, bottling, and storing the oil will be just about the same. Freshly pressed oil will be cloudy from small bits of seed and shell suspended in the oil. Allow the oil to settle in a cool, dark location. Label your oil, including the date of pressing. Within 24 to 48 hours, the oil will have visibly clarified, and most of the debris will have settled to the bottom of the container. Decant the oil, leaving the sediment behind, and then filter it through a fine-mesh screen or tightly woven cheesecloth. Filtering will increase the product's shelf life. While specific storage temperatures vary depending on the seed, keeping the oils in a cool, dark area is always best. This can be as easy as storing them in a kitchen cupboard or pantry. Some oils are more delicate and will benefit from refrigeration. While this isn't always necessary, cold storage will keep your oils from going rancid even longer — so when in doubt, opt for the refrigerator.

The crushed seed remaining after the extraction process, also known as the "seedcake," is also useful. If the oilseed had edible shells, such as hempseed or flax, or had its shell removed, such as walnut or pecan, the leftover seedcake is edible. Mill the seedcake into a powder using a food processor and add it to cereals, breads, and other baked goods. Or, if the seeds were pressed with their inedible shells on, like sunflower, you can still use the seedcake as a supplemental feed for your chickens or other livestock. You can also add it to the compost pile, where it’ll help produce a lush, rich soil.

Reviving traditional artisan skills, such as small-scale seed and nut oil pressing, revitalizes our relationship with our food system. This hands-on, small-batch approach to food production connects us to the land and to each other in ways far beyond what we could achieve as consumers. Let's press on.

Bevin Cohen is an award-winning author, herbalist, seed saver, educator, and owner of Small House Farm in Michigan. Bevin offers workshops and lectures on the benefits of living closer to the land through seeds, herbs, and locally grown food. He's a freelance writer whose work has appeared in MOTHER EARTH NEWS, Grit, Modern Farmer, and more. Bevin is the author of four books, including Saving Our Seeds and his latest book The Complete Guide to Seed and Nut Oils. Learn more about Bevin's work at Small House Farm.