(ELSD) in milled corn were triacylglycerols (TAG) and
free fatty acids (FFA). Using this method, fatty acids
are partially resolved and linoleic acid, as expected, is
the principal FA (Figure 2A). No UV-absorbing compounds
(295 nm) were detected in the hexane extract
of milled corn (Figure 2B). The amount of TAG in the
isolate appeared to be significantly less than that found
in milled corn (compare Figures 2A and 3A). This can
be attributed to lipase activity. No attempt was made
to prevent hydrolysis of the oil before extracting the
zein. There was, however, an unknown component in
the isolate that had the same elution time as TAG and
had an absorbance at 295 nm (Figure 3). This peak is
not due to TAG since they do not absorb radiation at
this wavelength. It was also determined by LC-MS that
the molecular mass of this compound was 396.5 Da,
significantly less than that of TAG. Two other major
components in the lipid fraction of the isolate were
phytosterols (St) and free phytosterol esters (FPE),
which, apparently, were concentrated during the isolation
procedure (Figure 3). A comparison of the lipid
composition for the milled corn and isolate indicates that
the TAG in milled corn was absent in the zein-lipid
isolate and a significant increase in the amount of St
and FPE occurred (Table 4).
For coated paper to be recycled, it is necessary that
the zein-lipid coating be removed enzymatically from
paper. That this could be done was previously demonstrated
for commercial zein-paraffin wax coated paper.
Proteases such as papain, pepsin, and thermolysin have
all been shown to be capable of digesting zein (Saito et
al., 1988; Yamada et al., 1995; Yano et al., 1996).
R-Chymotrypsin is preferable to the other enzymes