Industrial Use of Oil Cakes for Material Applications - The Economic Utilisation of Food Co-Products - page 146

d n 9 r 3 n g | 5

Figure 7.6 Reduction scheme of disulfide bonds by sulfite ion. 33

d y y f n n 3 .

Figure 7.7 Protein structural change occurring during the extrusion process. 24

sunflower protein isolate was only possible at processing temperatures below
the denaturation temperature. 28
To summarise the structural changes of protein during an extrusion process,
Areˆ as has proposed an interesting ''suspension model'' 24 presentedinFigure7.7.

7.2.6 Oilseed Protein-Based Materials
Two research groups have intensively worked on oilseed protein-based
materials: Jay-Lin Jane's group in Iowa State University and Franc¸ oise
Silvestre's one in INP Toulouse, respectively, on soybean and sunflower.
Excluding wet forming by casting - as it is not industrially viable for nonfood
applications - the main forming technology used to produce protein-based
materials is the thermomoulding or hot-pressing of flat sheets. Applying high
temperature and pressure surpasses the T g and T d and, as no flowing properties
are required, coagulation/association phenomena is favored. The resulting
materials have some mechanical properties ranging from highly resistant and
brittle materials to highly plastic materials (elongation up to 300%) depending
on the plasticiser nature and content. 34-38 They also exhibit some interesting
properties towards water when compared to carbohydrate-based materials due
to both coagulation and natural disulfide crosslinking. 37