The corn or rice bran oils (Table 22) (281).Olive-pomace

The typical composition of crude rice
bran oil (RBO) is 81–84% triacylglycerols, 2–3% diacylglycerols, 1–2%
monoacylglycerols, 2–6% free fatty acids, 3–4% wax, 0.8% glycolipids, 1–2%
phospholipids and 4% unsaponifiable matters. The wax content of RBO can be
somewhat variable (2–8%), depending upon cultivars and processing parameters. (278). Rice bran wax
(RBW) is composed of alkyl esters, steryl esters, hydrocarbons and others minor
constituents, and when saponified, it generates long-chain fatty acids,
long-chain fatty alcohols and phytosterols (279). RBW consists
primarily of even-numbered aliphatic waxy esters containing 44–64 carbons. RBW
is capable of forming an organogel even at wax concentrations as low as 0.5 wt%.
These esters consist of C22 and C24 fatty acids linked to C24 to C40 aliphatic
alcohols, with C24 and C30 being the predominant fatty acid and fatty alcohol
species, although there is some variation in the alcohols. RBW has a melting temperature
of 80–83?C. This melting point is intermediate of carnauba and candelilla waxes
which are widely utilized edible waxes and RBW can also form an organogel in
vegetable oil at lower wax concentrations than either of these two waxes (280).A
chromatographic analysis to measure the crystallizable wax content of different vegetable oils has been
done (281). In seed oils such
as sunflower, soybean or peanut, the compounds initially referred to as
“soluble esters” are identified as monounsaturated waxes, esters of long-chain
saturated fatty acids, and a monounsaturated alcohol, mainly eicosenoic
alcohol. Such waxes are absent from corn or rice bran oils (Table 22) (281).Olive-pomace oil is obtained by
solvent extraction of the olive pomace (milling by-products). Its TAG composition
is similar to that of VOO, but some of the minor compounds (e.g., waxes) may
differ significantly requiring the oil to be winterized (Table 23). Because solvent-extracted olive
oils contain a considerably higher amount of waxes than VOOs, the wax content
is used as a quality parameter and has also been used to detect VOOs adulteration
with lower-quality olive oil or olive pomace oil. (Table 24). The waxes most frequently
found in olive oil are C40, C42, C44, and C46. The EU has established a legal
limit for total wax esters C40–C46 in extra-VOO (250
mg/kg) and refined olive oil (350 mg/kg). Olive fruit skin has the most of the
waxes. Therefore, wax content of olive-pomace oil is higher than VOOs, since
pomace contains a greater proportion of fruit skin (282).