Encapsulation of tannase for the hydrolysis of tea tannins

Tannase was encapsulated in alginate, chitosan. carrageenan or pectin gel m atrices, and in the case of alginate coated with high or low molecular weig ht chitosan to reduce enzyme release. Cross-linking with glutaraldehyde als o improved enzyme retention. Activate enzyme preparations were obtained, al though carrageenan gels were unstable in tea, Tannase activity was evaluate d by reduction in centrifugable flocculated) tea solids, and a reduction in tea cream measured turbidimetrically after removal of flocculated solids. Tannin interactions with the polysaccharide gels increased the level of cen trifugable solids (flocculent) in the tea. An optimum bead formulation cons isted of an alginate core, coated with chitosan and cross-linked with gluta raldehyde. Both core and coating materials contained active enzyme. Beads w ere prepared in a single step procedure involving extrusion of alginate/tan nase solution into a hardening bath containing tannase-loaded, chitosan sol ution. Tannase retained hydrolytic activity through three successive batch cycles, for 3 total period of 39h processing, and tea cream was visibily; r emoved by treatment with the immobilized tannase. Activity remained stable during 1-month bend storage under refrigeration. (C) 2001 Elsevier Science Inc. All rights reserved.