Extraction and characterization of zein from corn gluten meal for use as a film former in capsule shells

Zein, a corn protein, have been used as a film former. It is a potential material for preparation of non-animal derived hard capsule shell. The objectives of this study were to prepare hard capsule shell from a commercial zein and zein extracted from corn gluten meal, a byproduct from corn processing industry in Thailand. The zein extract was characterized, comparing with the commercial zein. Zein films and hard capsule shells were prepared by using 70% v/v ethanol solution. Properties of the film and hard capsule shell were investigated. The results showed that hard capsule shells could be prepared from zein in ethanol solution by dipping method. The film and hard capsule shell made from zein extracted from corn gluten meal showed difference in mechanical properties and dissolution profile, comparing with those made from the commercial zein because it contained more hydrophilic amino acids which were miscible with the hydrophilic plasticizer, glycerol, used in the formulation. The formulation of zein film and hard capsule shell needed a plasticizer to provide elasticity and the preparation process required an optimum relative humidity such as 52% relative humidity in this study. The findings suggested possibility of utilizing zein in preparing hard capsule shell.