Protein particles with tuneable composition and physical properties,
such as internal and surface structure, size and protein density,
are interesting for their use as prefabricated structure
elements in high protein food, or for their application as targeted
delivery vehicles. This study has shown that changing interactions
of whey proteins during preparation of protein particles by
increasing calcium concentrations, led to different aggregated
structures and the formation of different protein particles in terms
of composition and physical properties. When no calcium was
present, the particles were spherical and smooth and had a relatively
low protein concentration (9% (w/w)) due to swelling. Upon
addition of 7.4 mM calcium, the particles still had the same regular
spherical shape as particles without added calcium, but had an
increased protein density of 19% (w/w). With the presence of
15.0 mM calcium, particles with a coarse and irregular shape were
observed and an even larger protein density of about 25% (w/w)
was obtained. For concentrations higher than 30.0 mM calcium
(until 400 mM), the particles transformed from spherical to shell-like, due to protein accumulation and subsequent aggregation
at the droplet interface The increased protein content of the
calcium containing particles compared to protein particles without
calcium makes them advantageous for their use in high-protein
foods. However, only a significant percentage of calcium was
retained in the particles. The findings of this work suggest that
changing the particle composition and the formation of different
shell thickness and porosity by means of calcium incorporation
may present a new tool towards the development of novel food
structure elements and targeted delivery vehicles with additional
nutritional benefits.