Controlled release of protein from hydrocolloid gel microbeads before and after drying

Casein entrapped within gel microbeads using alginate, amidated LM pectin, gellan gum and a system containing a mixture of these polysaccharides (pectin:gellan:alginate, 1/3: 1/3: 1/3), were obtained by ionic gelation in a high-pressure capillary apparatus. Hydrogenated vegetable fat was also added to produce the gel microbeads and protein release in all the systems was measured, including from freeze-dried capsules containing protein and fat. Encapsulation efficiency, capsule size and morphology were evaluated as well as the protein release profile. Encapsulation efficiencies from 83.7 to 90.7% were obtained for the protein capsules and from 71.8 to 95.4% for those containing protein and fat. Greater release was observed from gel microbeads without fat where alginate presented the greatest diffusion (100%) and the system with a mixture of polyssacharides, the best barrier, with protein retention of 90% after 240 min in solution. The fat containing gel microbeads presented good percent retentions and both the gel microbeads and the dry microbeads showed similar percentages for release. The majority of the systems studied showed a burst effect on release. Gel microbeads size distribution was similar, both with and without fat, and independent of the matrix material, the mean size being 150microm. The morphological observations showed that the gel microbeads were spheroidal with a homogenous distribution of fat droplets in the microcapsules. Agglomeration occurred on drying but many particles maintained a partially spheroidal form, with a configuration of solid material.