Industrial Use of Oil Cakes for Material Applications - The Economic Utilisation of Food Co-Products - page 149

d n 9 r 3 n g | 5

d y y f n n 3 .

Figure 7.8 Chemical structure of the chlorogenic acid.

Table 7.4 Protein distribution according to the classification of Osborne and
Campbell. 52

Protein class
(%/total proteins) Solvents SFC1 SFC2 SFC3

Globulins 1 m Na Cl 28.9 29.2 34.4

Glutelins NaOH, pH 11.0 17.3 25.3 23.2

Albumins Distilled water, pH 6.5 0.7 0.2 0.2

Prolamins Aqueous ethanol, 70% 2.1 3.2 3.0

Insoluble proteins 51.0 42.1 39.2

The analysis reveals a significant amount of phenolic acid: the chlorogenic
acid (Figure 7.8). Most of the time found polymerised, this compound is known
as a complexing agent of protein. 53,54 Their polyfunctional structure gives them
the ability to bind to other molecules by all kinds of secondary interactions
(hydrogen, hydrophobic and ionic). Under oxidative conditions they form a
very reactive quinone and induce covalent crosslinking. The high amount of
polyphenolic compounds is responsible for the dark green colouration of
sunflower protein isolate and is often considered as a major drawback (along
with its laxative properties) for the feeding value of SFOC.
The protein composition of SFOC, determined by the selective extraction of
proteins as described by Osborne and Campbell, is presented in Table 7.4.
There are few results available on the protein composition of SFOC in the
literature. Most of the results are given for sunflower dehulled cake meal or
defatted meal, rather than for industrial SFOC. The very low content of
recoverable albumins ( o 1%) and the high insoluble protein content (435%) is
related to the severity of the industrial treatment.

7.3.1.3 Structural Analysis of SFOC
Macroscopically, only hull fragments are distinguishable, they represent about
40% w/w of the SFOC (Figure 7.9). SEM analysis of these fragments revealed