These results indicate that: (i) there exists a critical
concentration of caseinate in the aqueous phase of ca.
1% w/w at which the emulsifying capacity was maximum.
At this concentration the mean droplet size was minimum.
(ii) At caseinate concentrations in solution above ca.
1% w/w the emulsifying capacity was constant and the
size distribution of droplets in emulsion was monomodal.
From this critical caseinate concentration the interfacial film
around the droplets may be saturated by the protein. Thus,
the excess of caseinate would participate in the formation of
multilayers and/or would be present in the aqueous phase,
with repercussions on the stability of the emulsions as will
be analysed latter. (iii) At caseinate concentrations lower
than 1% w/w the fresh emulsion shows some degree of
flocculation, which disappears in a dispersing medium, with
the presence of SDS; the size distribution of droplets in
emulsion was bimodal. That is, at low caseinate concentrations
(C!1% w/w), as the interface is not saturated by
the protein and/or in the absence of protein multilayers,
droplet flocculation occurred in the fresh emulsion.
In emulsions, SDS displaces any caseinate from the
interface and thus breaks up flocs formed from bridging
flocculation. The fact that there is a discrepancy between the
d3,2 values of SDS and non-SDS treated samples below 1%
caseinate hints that these samples are apparently bridge-
flocculated, and SDS-mediated displacement of interfacial
caseinate releases the droplets. SDS has no impact in the
emulsions containing 1% caseinate or more, since there is
enough protein there to fully saturate the newly formed
interfaces after emulsification, so no bridged flocs exist to be
broken up by SDS. Furthermore, the sharp drop in droplet
size in 1% protein (SDS treated samples) shows that this is
the minimum concentration of protein to fully cover the
newly formed interface during emulsification.