The application of spray and freeze drying to the same
formulation results into different surface composition in the
dried microcapsules. The surface composition of WPI–GA
(control) coacervates produced through spray and freeze drying
showed characteristics of both WPI and GA (Fig. 4A and B).
However, the O—C=O (C5) peak, indicative of acid/ester groups,
is significantly more intense compared to the those of WPI
and GA suggesting some interaction between WPI and GA oc-
curring during the complex coacervation process. Spray-
dried microcapsules had higher protein concentration at the
surface (high level of nitrogen) whereas the freeze dried mi-
crocapsules had higher concentration of polysaccharides (high
levels of oxygen and C—O) on the surface. The former may
be due to greater exposure of the air-droplet interface (very
high surface to volume ratio) and also due to the inability of
proteins to counter diffuse when the water is rapidly
evaporated. Moreover, whey protein instantly forms a skin when
it comes in contact with hot air (Adhikari, Howes, Shrestha,
& Bhandari, 2007). This difference between spray and freeze
drying (spray-dried microcapsules consistently had much
higher concentration of protein on the surface) was observed
for all the microcapsules (WPI-O-GA, WPI-P-GA and
WPI-P-O-GA).