Industrial Use of Oil Cakes for Material Applications - The Economic Utilisation of Food Co-Products - page 152

d n 9 r 3 n g | 5

Figure 7.11 Light (left 30) and electron (right 250) micrographs of extruded SFOC.

d y y f n n 3 .

Figure 7.12 DSC thermograms (endo up) of SFOC and ESFOC. Samples equili-
brated at 60%RH and 25 1C.

The apparition of fibrous aggregates could be credibly connected to a
complex process of association of the noncellulosic compounds of the mixture.
The globulins are effectively denatured by this treatment (Figure 7.4). From
DSC analyses, the peak corresponding to the globulin denaturation (around
160 1C for SFOC samples) disappears on the ESFOC thermogram
(Figure 7.12). This was observed even when the temperature of the extruder
(Figure 7.10) was lower than the temperature of denaturation measured in DSC
for a sample with 30% moisture content. 16 Two reasons could explain this
phenomenon: the local temperature rise in zones of higher stress 58 and the
influence of the shear.
Besides, further to the denaturation, temperature promotes a set of
association reactions involving the other protein fractions, the phenolic
compounds, possibly the ligneous byproducts released by the defibration of the
husk fragments and sugars (Maillard reactions). 24 This could explain the
apparent homogeneity observed in the scanning electron micrographs
(Figure 7.11). The protein corpuscles of the raw sunflower oil cake (Figure 7.9)
disappear after the treatment and the fibres are embedded in a continuous
matrix.