Arachis hypogaea belongs to the butterfly-banded legume family (Fabaceae). As an annual herbaceous plant, Arachis hypogaea reaches an average length of 30 centimeters, bears pinnately paired leaves and several yellow-crowned single flowers. After pollination, the carpophor of the carpel grows into the ground, where the geocarpic fruit ripens. The characteristic fruit, the peanut, together with the woody pod sheath is also botanically a nut. Only the protein- and fat-rich (approx. 45 percent) seed, which can also be eaten raw, has nutritive value, an exception among fabaceae.
Originally native to the Andes, the culture, which is over 8000 years old, first came to the Caribbean islands, Mexico and later to Africa, East Asia and North America. Today, its cultivation is widespread in all frost-free regions of the world. In 2019, the world's largest producer was China, with more than two and a half times the tonnage of India, the former main supplier. It was followed by Nigeria, Sudan and the United States.
Flowers appear about 30 days after sowing, followed another 80 to 150 days later by fruit maturity in mid- to late summer. The whole plants are pulled out manually or mechanically and pre-dried. Subsequent harvesting of the pods is done by hand or by combine harvester. This is followed by final drying from 40 to below 7 percent water content.
Yellowish and aromatic virgin peanut oil is extracted cold in screw presses from raw, shelled peanut seeds. Only flawless raw material is suitable for this purpose: Aflatoxins, for example due to improper storage, can only be eliminated via refining. Refined qualities are further processed first pressings, hot pressings or hexane extractions of pressing residues. For pharmaceutical purposes, the European Pharmacopoeia prescribes narrow specifications. Oils from roasted peanut seed and hydrogenated peanut fats are also available on the market.
The triglycerides of peanut oil vary greatly in their fatty acid composition. The monounsaturated oleic acid (35 to 69 percent) and the doubly unsaturated omega-6 fatty acid linoleic acid (12 to 43 percent) predominate. The native oil is thus richer in polyunsaturated fatty acids than olive oil and is more similar to rapeseed oil in this respect. However, omega-3 fatty acids are missing as a counterpart to be supplemented. Saturated palmitic acid (16:0) accounts for 8 to 14 percent. The contents of tocopherols (vitamin E) and other antioxidants are also remarkable. Roasted peanuts provide a particularly nutty and intense salad oil. Only gustatory neutral, colorless raffinates reach suitable smoke points of up to 230 °C for frying and deep-frying.
In pharmacy and medicine, peanut oil is useful as an ointment base, carrier for lipophilic active ingredients, or emollient in both topical and enteral or parenteral formulations. Peanut oil may assist in combating hypercholesterolemia. It is said to have beneficial effects on dry scaly skin and help soothe eczema (both chronic and atopic). As a cosmetic it is used in massage applications, bath additives, creams and lotions, when an oil that is only slightly absorbed is required.
Peanut oil is used industrially as a basis for vegetable edible fats, soaps, varnishes or paints.
Special caution is required in case of known peanut allergy: There is always a risk of anaphylactic shock. This is because even refined peanut oil can still contain traces of allergenic protein, depending on the degree of purification, albeit much less than cold-pressed.