In general, oils contain the highest
concentration of PS by weight, followed by nuts and oil seeds, whole grains,
spices and herbs, legumes, vegetables, and fruits. Refined grain products contain
lower amount of PS than their whole grain counterparts (28).
The majority of crude vegetable oils contain 1-5g/kg of PS. The most
significant exceptions are corn, rapeseed, rice bran and wheat germ oils which
contain higher amounts of PS (29).
Most common vegetable oils, including palm, soybean, rapeseed/canola, sunflower,
safflower, cottonseed, olive, peanut, coconut, and corn oils, and their phytosterol
composition, are discussed here.
Palm oil –
Palm oil is an oil extracted from the fleshy orange-red mesocarp of the fruits
of the oil palm tree (Elaeis guineensis) which contain 45% to 55% oil.
Oil is also extracted from palm kernel, which contains up to 50% oil (30, 31). Palm oil may be fractionated into
two major fractions: a liquid oil palm olein (65–70%, with melting point of
18–20?C) and a solid fraction stearin (30–35%,
with melting point of 48–50?C) (31).
The olein contains higher levels of oleic acid (39–45%) and linoleic acid
(10–13%) compared to palm oil (32).
Further fractionation of the palm olein
produces more unsaturated fractions, often called super- olein or double
fractionated olein. These have higher levels of oleic and linoleic acids,
ranging from 43–49% and 10–15%, respectively, resulting in iodine values (IV)
of 60–67, and have lower cloud points of about 2–5 °C. In contrast, palm oleins
with IV less than 60 have cloud points of 6–10 °C (32).
Palm oil has relatively low amount of PS
among common vegetable oils (33).
The total sterol content of palm oil ranges from 364–491 mg/L. The major
sterols in palm oil are ?-sitosterol (281.8 mg/L), campesterol (111.0
mg/L) and stigmasterol (56.0 mg/L) (31).
Palm oil contains less cholesterol than many other vegetable oils (32).
The total sterol content of palm kernel oil ranges from 700 to 1400 mg/kg.
?-Sitosterol (62.6-73.1%) is the major sterol present in palm kernel oil,
followed by stigmasterol (12.0-16.6%) and campesterol (8.4-12.7%) (34).
Concentrations of different desmethyl sterols in palm oil, palm kernel oil and
their fractions are presented in Table 2. PS content of palm superolein
fraction is minimum (100 mg/kg) among all other common vegetable oils.