Experimental data obtained was analyzed statistically by analysis of variance for statistical significance and multiple comparisons of means were accomplished with Duncan’s Multiple Range Test (p £ 0.05).

13.3 RESULTS AND DISCUSSION

13.3.1 FT-IR SPECTRAL INTERPRETATION

FT-IR is a common means to evaluate the chemical modification of lignocellulosic/ wood fibers.848’5563 Because the effect of solvent extraction and malation are a criti­cal aspect of this study, the FT-IR spectra are shown first, refer to Fig. 13.1.

The FT-IR of the untreated DDGS (Original DDGS) as shown in Fig. 1 indicates the following absorbance modes intensities cm1: 3377 (very strong), 3012 (weak — medium), 2926 (medium-strong), 2857 (medium), 1734 (medium), 1653 (strong), 1521(medium), 1451 (medium), 1374 (medium), 1238 (medium), and 1041 (very strong). The 3377 cm-1 band is a composite of the protein N-H and the O-H of the carbohydrate moieties present; whereas the small 3012 cm-1 band is that of the ole — finic — C=C-H stretching mode of the oil content. The 2926 and 2857 cm-1 peaks are, respectively the alkyl groups (-CH2-, -CH3), whereas the 1734 cm-1 and 1238 cm-1 absorption bands are mainly those of the oil component although both the carbohy­drate and protein components have a small contribution to the 2926 and 2857 cm-1 bands as well. The 3377 and 1041 cm-1 bands are mainly protein and carbohydrate contributions to the spectrum.

In the solvent (hexane/acetone) extracted-DDGS material (STDDGS) the in­tensity of the carbonyl band of the oil (1736 cm-1) decreased from 0.25 to 0.15 absorbance units as most of the oil was removed (Fig. 13.1). Following acetyla­tion (STDDGS/A) two bands 1743 and 1235 cm-1 were boosted in intensity. The ester — C=O (1743 cm-1) and the ester — C-C=O stretch (1235 cm-1) are observed. A competition between the malation-acetylation reaction (STDDGS/AM) resulted in an isolated product whose infrared spectrum gave a broadened 1730 cm-1 band ac­counting for the ester carbonyl.

The IR spectrum of the unmodified PW shown in Fig. 13.1 gives a characteristi­cally strong OH band around 3419 cm-1 and the — CH2O — band at 1047 cm-1, respectively. Also present is an unresolved band around 2928 cm-1 for the alkyls (-CH3, — CH2-) modes. There are also two reasonably sharp medium intensity bands at 1739 and at 1239 cm-1 that indicate carbonyl absorption bands betraying the presence of some oil in the wood. In addition, a pair of bands at 1622 and 1505 cm-1 occur that could represent the presence of some protein component in the wood.

The solvent (hexane/acetone) extracted PW (STPW) did not seem to have re­leased all its oil components since the its spectrum displayed the same intensity in the 1739 and 1238 cm-1 bands as the PW spectrum shown in Fig. 13.1. A noticeable change occurred in the amide I band of the protein which was attenuated. Upon acetylation (STPW/A), two noticeable changes were evident: the 3440 cm-1 OH band was truncated from about 0.85 absorbance units to 0.6 absorbance units. The major evidence following acetylation was the increase in intensity of the carbonyl band at 1744 cm-1 from 0.24 absorbance units in the unmodified to 0.55 units in the acetylated product. Following this was the corresponding increased intensity of the 1238 cm-1 band (-C-C=O) from 0.4 to 0.62 absorbance units, whereas the 1047 cm-1 band remained unchanged. The acetylated/maleate spectrum (STPW/AM) closely mimics the STPW/A spectrum.