total sterols (2.9 mg/g oil), followed by almond oil (2.7–2.
8 mg/g oil) and pecan oil (2.6–2.7 mg/g oil). Argan oil – Argan oil is produced from the kernels of the fruits of argan trees (Argania spinosa L.) (88). Cosmetic-grade oil is produced from non-roasted kernels.Cosmetic-grade argan oil is used for treating skin pimples, juvenile acne, chickenpox pustules and dry skin, and reducing the rate of appearance of wrinkles.
Dietary argan oil is traditionally considered to have several heath-beneficial properties. The oil contains 0.4–1.1% unsaponifiable matter containing carotenoids (37%), tocopherols (8%), sterols (29%), triterpene alcohols (20%) and xanthophylls (5%) (44). Argon oil contains between 142 and 220 mg/kg of PS. Sterol content of virgin argan oil is presented in Table 10. ?-sitosterol, the most common sterol in most vegetable oils, is absent in argan oil (89).
The major sterols detected in theargan oils are schottenol (mean 147±10 mg/kg) and spinasterol (mean 122±10 mg/kg) (88). These findings are important in detecting the adulteration of argan with cheaper vegetable oils.Grapeseed oil – Grape seed oil is obtained from the seeds left following pressing grapes to produce juice. Grape seeds contain 6-20 % wt of oil, which is usually extracted with solvent and refined before use. The total levels of sterol range from 258 to 1125 mg/100 g with an average value of 571 mg/100 g.
?-Sitosterol is the major sterol, comprising about 60–80% of total sterols, and followed by campesterol, stigmasterol and ?5-avenasterol. Grape seed oil also contains small amounts of steradienes, dehydration products of sterols formed during heating or refining process (90, 91). The content of steradienes in commercially extracted grape seed oils varies from 0.05 to 6.7 mg/kg (91).
Wheat germ oil – Wheat-germ oil (WGO) is a specialty product, which is used for itsnutritional value, specifically for its high vitamin-E content. Unlike common oils such as soybean and canola oils, which are mainly used for their heat-transfer properties during cooking and for providing a pleasant mouth feel in salad dressings. The oil content of wheat germ varies with the variety, the purity, and the extraction method. Commercially flaked wheat germ contains 7–11% oil (92).WGO is relatively rich in unsaponifiable matters, particularly PS, n-alkanols, and tocopherols. PS are a major constituent in the WGO unsaponifiable fraction (about 35%). Sitosterol (60–70%) and campesterol (20–30%) are the two main PS present in WGO (92).
PS are known to accumulate in the bran and germ fractions of the wheat grain, whereas steryl ferulates are mostly found in the bran (93). The majority of the PS in WGO are present in esterified form. Cycloartenol, ?-amyrin, and 24-methylene cycloartanol are the major triterpenols, which constitute less than 1% ofWGO (92).Avocado oil – The cold-pressed avocado oil is rich (2–7%) in unsaponifiable matters, including 2230–4480 mg/kg of PS (mainly ?-sitosterol, 81–92%), 70–190 mg/kg of tocopherols, mainly ?-tocopherol (110mg/kg), and many unidentified components (50). Like other common vegetable oils, sitosterol is the main plant sterol present in avocado oil (81–92%).
Other sterols such as ?5-avenasterol, campesterol, and stigmasterol are also present at much lower concentrations.Vegetable oils can be extracted in different ways, including by press or solvent. Oil extraction by press is for oilseeds with oil content higher than 20%. However, oilseeds with oil content lower than 20%, such as soybean oil, should be extracted by solvent. Press methods can also be divided into cold or hot press.
Oil extractedby solvent or hot press has to be refined, but there is no need to refine cold press oil. Solvent extraction is more effective on the extraction of sterols than cold pressing.