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240 Advances in Eco-Fuels for a Sustainable Environment

2%–5%, respectively. Crude RBO is extremely rich in bioactive compounds, account-
ing for 4%–6% of the oil [6, 14, 31, 32].
Among the bioactive compounds, γ-oryzanol, which accounts for 1%–3% of the
total oil, is unique to RBO. It is known to be a potent hypocholesterolemic agent.
Tocols (tocopherols and tocotrienols), of which more than 70% are tocotrienols, com-
prise up to 0.06% of the total oil [32]. This level is comparable to that found in palm
oil, which is known as a good source of tocotrienols [33]. Tocotrienols possess greater
in vivo antioxidant potency than α-tocopherol. Immunomodulation, antiplatelet
aggregation, and antithrombotic and anticancer activities are the other health attri-
butes of tocotrienols. RBO with up to 3wt% phytosterol content [32] has the distinc-
tion of possessing the highest level of these constituents in common vegetable oils.
Recent evidence suggests that consumption of about 1g of phytosterols per day
can bring down blood cholesterol levels by 10%–15%. A substantial amount of squa-
lene also exists in RBO. The balanced fatty acid composition (16:0, 15%; 18:0, 1.5%;
18:1, 44%; 18:2, 35%) is yet another attribute of RBO. However, crude RBO has been
difficult to refine because of its high FFA, acetone-insoluble content, and dark color
[5, 14]. Table 9.1 shows the composition of crude RBO.
Composition of acylglycerols (AG) and FFA for RBO extracted from various rice
bran samples may vary significantly. Stabilization of rice bran can keep the quality of
RBO. However, additional production cost is needed if stabilization of bran is prac-
ticed. FFA as much as 6%–8% has been found, even in oil that was extracted from bran
immediately after milling [5]. Crude RBO produced by hexane extraction is dark

Table 9.1 Composition of crude RBO

a b c
Property CRBO CRBO CRBO
I. Saponifiable lipids 90–96 … …
1. Neutral lipids, % of total lipids 80–85 … …
Triglycerides (TG) 66–77 81–84 …
Diglycerides (DG) 2.4–3.6 2–3 3.9
Monoglycerides (MG) 4.7–6.2 1–2 …
Free fatty acids (FFA) 2–4 2–6 7.53
Waxes 3–4 … …
2. Polar lipids … … …
Glycolipids 5.4–6.7 0.8 …
Phospholipids 3.6–4.8 1–2 …
II. Unsaponifiable lipids 4.2 4 5.4
Phytosterols 2.4 … 2.94
Hydrocarbons 0.8 … …
Tocopherols 0.04 … 0.021
Tocotrienols 0.07 … 0.056
Oryzanol … … 1.8
a
[31].
b
[14].
c
[32].