Results and discussion
3.1. Fractionation of SFM
Fig. 2 presents the mass balances and the protein content of
each fraction achieved via SFM fractionation. The LF was 31% of the
wholeSFMdry mass and contained almost 20% of the initial protein,
while the PF was 50% of the SFM mass (db) with a 69.5% of the initial
protein content. The soluble fraction contained soluble proteins
(10.5% of the initial protein content) and sugars. After the extraction
of phenolic compounds, the PF was sequentially treated with alkaline
and acidic solutions to produce the PI that constituted 34.6% of
the initial protein contained in SFM. The co-product streams produced
during PI separation were the SR with a significant protein
content of 28.2% of the initial protein content and the supernatant.
The purity of PI was 95.8%. The PI could be used in the food industry
or in novel applications including biopolymers, amino acid isolation
and edible films (Ordonez et al., 2008; Rodrigues et al., 2012;
Salgado et al., 2012). PI and various hydrolysates are currently
under evaluation as adhesives for wood-based panel applications
with promising results (data not published yet).