Description
The peanut is an annual plant with yellow flowers from 20 to 90 cm in height.
The leaves are composed of two or three pairs of membranous, oval leaflets. They are provided with sheathing stipules at their base.
The flowers are almost sessile and appear in the axils of the leaves, singly or in small groups. The papilionaceous corolla is orange-yellow. The nine stamens are welded into tubes by their threads. The ovary is inserted on a particular support, the gynophore.
After fertilization, the ovary is carried to earth by the development of the gynophore which lengthens while bending towards the earth by positive geotropism3.
The fruit ripens to a depth of 3 to 5 cm. It is a plant which therefore requires light and well-drained soil. The fruit is a pod 3 to 4 cm long, known commercially as a shell. The multiseminate pod with longitudinal dehiscence, typical of the Fabaceae, undergoes a morphological modification4: it becomes pauciseminate and indehiscent, externally reticulated and strangled between the seeds (most often only two). The ovoid seeds are wrapped in a dry red seed coat.
Micronutrients
Peanuts are a good source of magnesium (50.6% of the RDA) and phosphorus (57.1% of the RDA) and manganese (70% of the RDA).
They are also an excellent source of vitamin B (especially niacin, vitamin B3) and vitamin E.
Phytochemicals
Peanuts contain phenolic compounds, such as p-coumaric acid (2.53 mg / 100g and resveratrol (0.07 mg / 100g) as well as flavonoids (189.8 mg / 100g).
Roasted peanuts contain 61 to 114 mg / 100g of phytosterol, depending on the variety. The main component is beta-sitosterol at 78 to 83%.
The pod, an abundant byproduct of peanut production, also contains many consumable bioactive compounds, polyphenols, flavonoids, luteolin, carotenes and isosaponaretins.
In a comparative study of the phenolic content of ten commercial nuts, Yang et al. have carried out a solvent extraction of free and bound phytochemicals. They established by the Folin-Ciocalteu colorimetric method that the common walnut had the phenolic content (1 580 mg / 100g) by far the greatest with the pecan nut (1 464 mg / 100 g), followed by the peanut, the pistachio (572 mg / 100 g), cashew (316 mg / 100 g), hazelnut (315 mg / 100 g) and almond (213 mg / 100 g)
Allergy
Some people suffer from an allergy, sometimes very acute, to certain peanut proteins. The prevalence is around 1%, and is increasing. This allergy is responsible for more than half of the deaths due to a food allergy.
The treatment is based on the total eviction of peanuts and all derived products, imposing a rigorous and often complex diet, as well as the availability of anti-allergic treatment on site in the event of accidental exposure. The effectiveness of desensitization is imperfect and inconsistent, but in some cases may allow tolerance to small doses of peanuts.
Peanut allergy is often crossed with lupine allergy.
To avoid the risk of allergy, the airline EasyJet eliminates in 2019 the sale of peanuts on board its planes.