3.5. The mechanism of aqueous enzymatic extraction of protein and
oil bodies
The mechanism of the protein and oil body extraction through the
enzymatic hydrolysis of the peanut cell wall is presented schematically
in Fig. 8. Proteins and oils are present in peanut cotyledon cells in
the form of protein bodies and oil bodies. The cell wall, which is
composed of cellulose, hemicellulose, and pectin, maintains the cell
structure and inhibits the release of proteins and oils. In the aqueous
enzymatic extraction process, mechanical crushing is an important step
that destroys the peanut cell wall and promotes the release of proteins
and oil bodies. We used the conventional dry crushing in this study to
break the chain structure of the cell wall and decrease the peanut
particle size. However, dry crushing destroyed only a part of peanut
cells, and therefore not all protein and oil bodies were released. In
contrast, Viscozyme® L degraded sufficiently the
structure of the cell wall by acting on the C-O stretching, C-C
stretching, and CH2 symmetrical bending of cellulose,
the C-O stretching and O-C-O asymmetrical bending of hemicellulose, and
the C-O stretching and C-C stretching of pectin, and thus facilitated
the release of oil bodies and proteins from peanut cells. After
centrifugation of the extract, which contained proteins, oil bodies, and
the enzymatic hydrolysate of cell wall
polysaccharides, oil bodies exist in the upper
layer of the aqueous phase, while proteins and enzymatic hydrolysate are
in the aqueous phase.