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IV. Resultados y discusión. Capítulo I 101
3.6. Sample microstructure
Figure 3 shows the CLSM images of almond milk untreated and
submitted to different treatments. Oil droplets and protein bodies dispersed
in the serum phase are clearly distinguished in Figures 3 A and B for the
untreated milk. A certain degree of flocculation in protein bodies can be
observed, which can be due to their hydrophobic character. Most of the
almond proteins belong to the oleosin family with low-molecular-weight
and poor water solubility, due to a long highly hydrophobic domain of about
70 amino acid residues (Beisson et al., 2001). In some cases, protein bodies
appear adsorbed on the oil droplet surface, forming bridges between them.
The low affinity of proteins by the aqueous medium contributes to the low
stability of the obtained emulsions where steric stability did not occur due to
the poor solvent effect (McClements, 2005).
In LH treated samples (Figures 3 C and D), protein aggregates can be
observed to be spread over big areas in the sample, whereas isolated protein
bodies are not frequently present. In many cases, protein aggregates include
oil droplets. This observation is coherent with described rheological
behaviour where LH treatment gives rise to a plastic fluid with yield stress
and higher apparent viscosity, which may be due to the formation of a weak
gel, associated with a three-dimensional network of aggregated particles at
relatively low concentration.