Droplet size, size distribution and zeta-potential are important
indicators for emulsion stability. For encapsulating hydrophobic
core materials by spray drying, obtaining stable emulsions prior
to the drying process is crucial to ensure the production of good
quality shelf-stable powders. Table 2 shows that the average droplet
size of the emulsions before spray drying is below 200 nm while
the size distributions (PDI) are 0.15 and 0.11 for the WPI/SCF70 and
the SC/SCF70 systems respectively. PDI values greater than 0.1
indicate polydispersity and values between 0.1 and 0.25 indicate
a narrow size particle distribution. These results imply that the
homogenization method employed in this study was suitable to
produce emulsions with fine droplet size. Sufficient emulsifier
(WPI and SC) was present in all cases to confer interfacial stability
to emulsions, as evidenced by the small average droplet size. During
the microencapsulation process, small emulsion droplet size
confers advantages in terms of emulsion stability, retention of oil
in the dried powder and less extractable surface oil (Hogan et al.,
2001).