In vitro release test
Curcumin release profile both in SGF and SIF was measured and
presented in Fig. 9. Compared with raw curcumin, cur@star 3 wt%
exhibited a burst release profile in which maximum level of curcuminwas
achieved within 30 min. It is also notable that release in
SIF was faster than that in SGF for both raw curcumin and cur@star
3 wt%. The different pH value may be responsible for the observed
release speed difference as H bonding between curcumin and
starch is highly influenced by the environmental pH value (Jin, Liu,
Zhang, Chen, & Niu, 2006). The burst release of cur@star 3 wt% may
be attributed to the way of sample preparing (O'Toole et al., 2012).
During freeze drying, water molecules were removed which made
the sample poriferous and readily dissolved in solution. We tested
the release profile of pressed cur@star sample (like tablet) which
showed similar release profile at much decreased speed (data not
shown). In both SGF and SIF, partial curcumin was trapped in the
starch matrix hence the full release of curcumin was not observed
even with extended incubation time.