A sodium dodecyl sulfate polyacrylamide gel
electrophoresis (SDS-PAGE) analysis showed that storage proteins
in olive seed mainly consisted of two hydrogen-bonded subunits
of 41 and 47.5 kDa [4–6]. Moreover, the precursor of 41 kDa
generated three polypeptides of 21.5, 25.5, and 27.5 kDa when
reduced, while the other precursor yielded two polypeptides of
20.5 and 30.0 kDa [4]. In addition to these storage proteins,
proteins associated with fatty bodies called oleosins are hydrophobic proteins from oleaginous seeds stabilizing oil bodies. The oil bodies are composed of a core of triacylglycerols surrounded
by a monolayer of phospholipids in which different proteins are
inserted [7]. Oleosins are insoluble in water, but could be easily
dissolved using a surfactant such as SDS, according to Huang
et al. [8]. Ross et al. [9] found two different oleosins of 22 and
50 kDa in olive seeds. The 22 kDa protein was assigned to an
oleosin located on the surface of the oil bodies. These authors [9]
also analyzed the oil bodies from the olive mesocarp tissue not
detecting any oleosin. However, the mesocarp contains proteins
(1.3–1.8% of the dry weight of the olive fruit) that are still not
well-known [1]. Indeed, Hidalgo et al. [10] reported that some
proteins present in the oil bodies of the olive fruit mesocarp could
pass to the oil during their extraction. Moreover, Zamora [1]
found a polypeptide of 4.6 kDa by SDS-PAGE analysis regardless
of the variety of the olive fruit or the maturity stage.