Colloidal stability
Soymilk is a water extract of soybeans in the form of oil-in-water emulsion.
The most relevant functional property of proteins in this system is to cover oil droplets of the lipid fraction for maintaining a good dispersibility of those in the continuous phase during storage.
Thus, soy proteins make soymilk to be a very stable emulsion.
In spite of this aggregation of oil droplets, creaming, and sedimentation of solid particles are common ways of destabilization of vegetable beverages.
Those phenomena are dependent to a great extent on particle size distribution.
Particles in soymilk include not only fat globules, but also small particles,such as protein bodies, protein aggregates and even protein-fat globule and globule aggregates.
Untreated and pasteurized soymilk presented the highest values of particle size parameters as described in previous study of own group.
Results demonstrated that UHPH-treated soymilk showed higher reduction in the particle size parameters compared to pasteurized soymilk.
Those results of particle size were supported by particle sedimentation through low-speed centrifugation during 28 days of storage (Table 1).
Particle sedimentation measured by centrifugation is indirectly related to the stability of the system.
This analysis can be considered as indicative of the sedimentation potential of soymilk during long storage periods and especially as a comparative measurement among treatments applied.
Pasteurized soymilk presented higher amount of solids settled by centrifugation than UHPH soymilks throughout 28 days of storage (Table 1).
As storage time increased, a slight increase in the percentage of sediments was observed, and differences were especially marked from 14 days of storage.
Solids sedimentation values in UHPH samples were very reduced and only slight increase was observed at day 28 (p b 0.05).