Characterizing internal cavity modulation of corn starch microcapsules


Wulff, D., Chan, A., Liu, Q., Gu, F.X., Aucoin, M.G. (2020). Characterizing internal cavity modulation of corn starch microcapsules. Heliyon, [online] 6(10),

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Despite extensive research over the past many decades, starch structure is still not fully understood. Little is known about what is happening structurally inside a starch granule through the gelatinization process. The internal architecture changes that occur through the gelatinization process have been poorly characterized.
In this paper, the swelling extent (i.e. how swelled the particles are) is characterized through measurement of the swelling power. The internal structure of the corn starch was observed at various stages of swelling through characterization with scanning electron microscopy, brightfield microscopy, polarizing light microscopy, and confocal laser scanning microscopy.
We find that the swelling process causes growth of the internal cavity. The growth of the internal cavity is primarily the result of particle expansion, and only a small increase in particle diameter corresponds to a large increase in the internal cavity volume. The particle shell becomes thinner while the structural integrity of the particle appears to be largely maintained. Both the swelling process and how the internal cavity changes as a result of the swelling were also mathematically modeled and fit to our experimental data. The research will provide new knowledge on starch structure and information for starch modification and applications in pharmaceutical, packaging, paper, plastic, cosmetic, and medical industries


Swelling of normal corn starch granules through heating in water leads to enlargement of the starch particles and a corresponding increase in internal cavity size. Through control of the swelling extent, it is possible to tune the size of the internal cavity for the starch microcapsules (SMCs). The swelling extent can be controlled through regulation of the swelling time and the swelling temperature. Since the swelling extent is correlated with particle size and solubility, these aspects may also be controlled. Imaging the SMCs at increasing levels of swelling extent using scanning electron microscopy (SEM) allowed for the internal cavity swelling process to be clearly observed. Brightfield and polarizing light microscopy validated the SEM observations. Confocal laser scanning microscopy provided further validation and indicated that it is possible to load the SMCs with large molecules through diffusion. The highly tunable SMCs are novel microparticles which could have applications in various industries.

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