The yield in protein concentrate of the overall process is approximately 10% by
weight of faba seeds. The protein concentrate obtained by spray drying is a powder
of whitish colour and it appears as spherical agglomerates of diverse sizes. The
protein obtained by freeze drying is a darker color than that obtained by spray
drying and is in the form of strands.
A study of the particle size distribution of both powders was carried out by laser
diffraction using a Coulter Counter LS 130 particle size analyzer. In Fig. 1 these
distributions are shown for the protein powder dried by freeze drying and spray
drying. In the case of the lyophilized powder the Sauter mean diameter of particle
is 34.62 mm, with the 90% being between 8.18 and 76.03 mm. In the case of the
spray dried powder the Sauter mean diameter is 10.98 mm, whit 90% of it being
between 3.13 and 2155 mm. The powder dried by spray drying is more uniform with
a size 32% lower than the lyophilized power. This fact has a great importance when
evaluating the hygroscopicity of both protein powders.
The first step in the study of the functional properties of both powders was the
determination of their protein contents. The protein content that remains after
spray drying and freeze drying is high. The spray drying method is less damaging
(practically 100% of original protein), while with freeze drying there is a denaturation
of 10%.
The solubility of both powders (Fig. 2) is not high (less than 50%) and it
decreases with protein concentration. However, over the interval of studied concentrations,
the protein solubility of the material obtained by spray drying is higher, but
this difference decreases with the protein concentration. Due to their low solubility,
these proteins will not be highly effective in the processes of jellification, emulsification
or foam formation. The protein particles will not give high and rapid
dispersion, nevertheless, the diffusion of the protein across the water/air or water/oil
interface will be facilitated due to that the protein surface probably contains hydro-