3.4.2 Sterols contents
The
content and composition of phytosterols in RBO extracted using various
methods were listed in Table 3. It was found that the levels of
phytosterols in RBO obtained by AEE was much higher compared with that
of
SEO.
It was in agreement with Konopka, Roszkowska, Czaplicki & Tańska (2016)
who reported that higher phytosterols content in the enzyme-extracted
oil. While, it was different from the results of Nyam et al. (2009) that
the Kalahari melon seed oil extracted by organic solvents contained
higher sterols
contents.
As could be seen in Table 3,
the
predominant sterols in RBO were β-sitosterol (50% of total sterols),
followed by campesterol,
stigmastanol
and
stigmasterol.
It indicated
that
enzymatic treatment can release more antioxidant compounds from rice
bran due to the hydrolysis of cell
walls.
In addition, enzymatic hydrolysis can reduce the degree of interaction
between antioxidants and proteins, polysaccharides and pectins in the
bran and promote their release into oils (Fang, Du, Luo & Jin, 2015).
The lower content of unsaponifiable compounds in SEO
might
be due to the low polarity of n-hexane.
3.4.3Squalene
contents
Squalene
is a highly unsaturated aliphatic hydrocarbon
(C30H50), which is widely found in olive
oil, soybean oil and peanut oil (Chanioti & Tzia, 2019). Previous
studies have shown that squalene has natural antioxidant activity, which
makes it widely used in cosmetics. However, phenols and tocopherols are
the main antioxidants in oils, which makes the antioxidant activity of
squalene less obvious (Psomiadou & Tsimidou,
1999).
Comparison of AEEO and SEO showed significant (p <
0.05) differences of squalene
contents
which were
2962.56
mg/kg and 2479.56 mg/kg, respectively.
It
indicated that AEE promoted the release of squalene compared with SE.
The contents of squalene obtained by extraction were much less compared
with that by cold pressing (3189 mg/kg) (Pokkanta, Sookwong, Tanang,
Setchaiyan, Boontakham & Mahatheeranont,
2019).
It
illustrated that the content of squalene in crude oils depended on the
different extraction methods.