Ice cream samples containing either no stabilizer or CMC/guar at either concentration
showed similar d4,3 values (Table 3), which were slightly higher than their
respective mixes, indicating that some fat destabilization had occurred during freezing.
In general, during freezing of ice cream, the emulsion undergoes partial coalescence
or fat destabilization in which clumps and clusters of fat globules form an
internal fat structure into frozen product by entrapping air within the coalesced fat,
typically leading to larger d4,3 values in ice cream than the ice cream mix (Goff 1997;
Bolliger et al. 2000; Eisner et al. 2005).
Samples containing BSG showed considerably higher values than the unstabilized
or CMC/guar-containing ice creams, with 0.2% BSG being considerable higher than
0.1% BSG. Due to the presence of the BSG aggregates seen in the mix, it is not
possible to determine the extent of fat destabilization per se. However, what is evident
is that the BSG is also establishing a network structure in the ice cream, perhaps through
interactions with fat or protein, leading to larger particle size distributions, slower rates
of meltdown, and higher mix viscosity. Adsorption of BSG at oil–water interfaces in
emulsion model systems and its ability to lower the interfacial tension at the interface
have been recently reported (Osano et al. 2010). A number of other polysaccharides also
show emulsifying properties besides their functions as texture modifiers or stabilizers.
Their surface-active properties can be attributed to either hydrophobic groups or proteinaceous
moieties associated with them (Dickinson 2003).
The effect of increased emulsification level and structure formation by using BSG
in the ice cream was confirmed using cryo-SEM (Fig 2). As emulsification increased,
more fat globules could be seen at the air interface and these globules seemed to
penetrate further into the air bubble with increased BSG concentration. This behavior
of fat globules could be expected based on increased hydrophobicity of the fat
globule surface (Bolliger et al. 2000).