Date oil in the cosmetics industry
World’s date fruit production is on the rise, reaching 9.5 million tonnes on 1.236 million ha in 2020, according to the latest FAO data (Avg. 2022). There are several thousand different date varieties, which vary in shape, size, and weight (Al-Farsi & Lee 2011, Lemine et al. 2014). At the same time, co-products from the date fruit industry (date flesh and seeds) have become an environmental problem for the growing and processing areas. Date seed represents 10–15% of fresh fruit weight, which roughly accounts for 1–1.5 M tonnes of 2020 production.
The date palm tree, Phoenix dactylifera L., is an extremely important subsistence crop in North Africa (Levine et al. 2014). FAO data (2022) indicate that dates are mostly cultivated in Asia and Africa, the largest producer in 2020 being Egypt (1.7 million tonnes), followed by Saudi Arabia (1.54 Mt), Iran (1.3 Mt), Algeria (1.15 Mt), Iraq (0.74 Mt), Pakistan (0.54 Mt) and Sudan (0.47 Mt). In countries like Mauritania, dates represent a source of income for 16% of the inhabitants living in the date-producing regions (Lemine et al. 2014).
Date seeds are currently mainly used as animal feed and coffee replacement, but due to their valuable chemical composition they can be valorised as higher value-added applications. Date seeds contain 5–13% of oil, which consists of saturated and unsaturated fatty acids with lauric and oleic as the main ones (Besbes et al. 2004, Mrabet et al. 2020, Jemni et al. 2021). Tocopherols, tocotrienols, phytosterols, and phenolic compounds, which are substances with interesting bioactive properties, are also present in significant amounts (Besbes et al. 2004, Mrabet et al. 2020, Jemni et al. 2021).
Chemical composition and bioactive compounds
Date seed is mainly composed of dietary fiber, protein, carbohydrates, phenols, and minerals (potassium, magnesium, calcium, phosphorus, sodium, and iron). The composition varies among date varieties: proteins 4.3–6.1%, lipids 5–13%, and total sugars 1.8–83.1% of dry matter basis (Jemni et al. 2021). Date seed oil contains (i) saturated fatty acids composed of capric (C10:0), lauric (C12:0), myrsitic (C14:0), pentadeconic (C15:0), palmitic (C16:0), heptadecanoic (C17:0), stearic (C18:0), arachidic (C20:0) and behenic (C22:0), (ii) monounsaturated fatty acids (MUFA) composed of palmitoleic (C16:1), cis-10-heptadeconic (C17:1), oleic (C18:1), cis-11-eicosenic, gadoleic (C20:1), and (iii) polyunsaturated fatty acids (PUFA) composed of linoleic (C18:2) and linolenic (C18:3) (Besbes et al. 2004, Mrabet et al. 2020, Jemni et al. 2021). Oil is characterized by the presence of five major fatty acids, which account for more than 90% of the total fatty acid contents: oleic acid (C18:1), linoleic acid (C18:2), palmitic acid (C16:0), myristic acid (C14:0), and lauric acid (C12:0 (Mrabet et al. 2020, Jemni et al. 2021). Depending on the date’s variety, saturated fatty acids can range from 26 to 50% and unsaturated from 45 to 71%.
Potential use in cosmetics
Due to the bioactive compounds in date oil, which have antioxidant, antibacterial, and antiviral activities, date oil has great potential in cosmetics products. The oil content in seeds depends on the date variety, harvest time and location, particle size, and extraction method (Mrabet et al. 2020). Oil is liquid at room temperature, yellowish in colour, and has a pleasant odour. It has advantageous physico-chemical characteristics for use in the cosmetic industry, so its composition is well suited for cream, soap, shampoo, and lotion formulations. Iodine value (IV) is lower than 100, classifying it as a non-drying oil. Acidity was measured in the range of 1–2.2 mg KOH/g (Besbes et al. 2004, Jemni et al. 2020, Mrabet et al. 2020). The Saponification value (SV) is high (198 to 228 mg KOH/g oil), which indicates very high content of low molecular weight triacylglycerols. This is a desirable characteristic for the use of date seed oil in the production of liquid soaps and shampoos.
Direct supplementation or replacement of skin lipids can be explored in the prevention or treatment of skin pathologies (Moore et al. 2020). Linoleic acid is one of the most essential ingredients to repair skin barrier damage and is indispensable for healthy skin growth (Jemni et al. 2021). Oil also contains tocols (commonly known as vitamin E) which are very efficient natural antioxidants, protecting biological membrane components. They also protect oil from free radical damage, thus contributing to its stability (Jemni et al. 2021). They are more effective than the synthetic antioxidant butylated hydroxytoluene (BHT). The average tocol (tocopherols and tocotrienols) content in date seed oil is 70.1–74.1 mg/100 g, which is higher than those of olive oil (23.39 mg/100 g oil) (Besbes et al. 2004, Mrabet et al. 2020, Jemni et al. 2021). Resistance against oxidation of date seed oil is also due to low polyunsaturated fatty acid content, which are more sensitive to oxidation, and phenolic compounds, sterols, tocopherols and chlorophylls (Besbes et al., 2004). The average total phenolic content of date seed oil was measured from 0.64 to 1.27 mg/g, which is significantly higher than in olive oil. The major components of date seed oil sterols were sitosterol, campesterol, and D5-avenasterol, while other minor sterols were cholesterol, stigmasterol, D5,24-stigmastadienol, D7-avenasterol, and D7-stigmastenol (Mrabet et al. 2020).
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