Impact of gelatine coating on the performance of tannin-loaded pectin microbeads obtained through external gelation

Abstract

One of the limitations of external gelation for microencapsulation is that small water-soluble compounds tend to diffuse out of the microbeads, resulting in low encapsulation efficiencies. In this work we propose a one-step approach for hydrogel microbead formation and simultaneous coating using external gelation. We explored amidated pectin as the encapsulation matrix for two different tannin-rich extracts (from chestnut and quebracho). The inclusion of tannin extracts contributed to the improvement of the structure of the microbeads through their interactions with pectin. By adding gelatine to the gelling bath, the microbeads were coated with the protein. This led to a significant increase in microencapsulation efficiency, which in some cases almost doubled compared to non-coated microbeads. Thanks to the binding of tannins with gelatine, coated microbeads loaded with the greatest amount of tannin extracts (20% w/w) presented the best retention of the bioactive compounds. A 14-days storage release study showed that these microencapsulation systems only experienced a slight loss of tannins during this period, with quebracho extract exhibiting greater retention than chestnut extract. Overall, by exploiting interactions in the pectin/tannins/gelatine ternary system, the proposed strategy for microbead production and coating in a single step allowed the development of a simple and more efficient microencapsulation approach for tannin extracts through external gelation.