Blends of gelatin with up to 50% hydroxypropylated high amylose (80%) corn starch were developed
as capsule materials. Poly(ethylene glycol) (PEG) was used as both a plasticizer and a compatibilizer in
the blends. In order to prepare hard capsules for pharmaceutical applications using the well-established
method of dipping stainless steel mold pins into solution, solutions with higher solids concentrations
(up to 30%) were developed. The solutions, films and capsules of the different gelatin–starch blends
were characterized by viscosity, transparency, tensile testing, water contact angle and SEM. The linear
microstructure of the high amylose starch, and the flexible and more hydrophilic hydroxylpropylene
groups grafted onto the starch improved the compatibility between the gelatin and starch. SEM revealed
a continuousphase of gelatinonthe surface offilms fromall blends. The water contact angle ofpure gelatin
and the different blends were similar, indicating a continuous phase of gelatin. By optimizing temperature
and incubation time to control viscosity, capsules of various blends were successfully developed. PEG
increased the transparency and toughness of the various blends