Pomegranate seed oil-loaded particles of the zein cross-linked with citric acid

Zein was cross-linked chemically with citric acid in the presence of sodium hydroxide as the reaction catalyst. Water was then used to desolvate the zein and generate core-free or pomegranate seed oil-loaded particles. Mean size of the particles obtained from noncross-linked and cross-linked zein was 350 and 246 nm, respectively. Cross-linking reaction caused an increase in the oil encapsulation efficiency. Scanning electron microscopy revealed the spherical morphology of particles. Fourier transform infrared (FTIR) spectroscopy confirmed the occurrence of chemical linkages between citric acid and zein. As well, it suggested that oil entrapment inside the zein particles was merely physical. Particulation of zein increased the upper limit of the glass transition phenomenon of biopolymer from 78C to ∼120C. The glass transition temperature (Tg) was also affected by the cross-linking of zein and oil encapsulation. The amount of encapsulated oil released from particles via the peptic hydrolysis was lower for the cross-linked sample.