Chitosan/clay nanocomposite films as supports for enzyme immobilization: An innovative green approach for winemaking applications

Protein haze formation in white wines during storage is considered the most important instability phenomenon of non-microbial origin. The use of proteolytic enzymes, covalently immobilized on solid supports, has recently proved to be a promising approach for reducing the haze potential of white wines. In this study, supports based on chitosan and nanoclays were produced by solvent casting technique, and investigated for use as a covalently linked bromelain carrier in wine-like medium. Various kinds of nanoclays were tested, including montmorillonite, sepiolite and bentonite, in different amounts (1-5% w/w with respect to chitosan). More specifically, unmodified and organically modified clays and an activated bentonite authorized for contact with food (i.e. OPTIGEL CK) were considered, and their effect on the final microstructural, thermal and mechanical properties of the obtained composite systems was investigated, on the basis of their different chemical composition, morphology, hydrophilicity/hydrophobicity and surface charge, resulting in different interactions with the polymeric matrix and a different enzyme loading. The nanocomposite films were used as innovative supports for the covalent immobilization of pineapple stem bromelain, selected as reference enzyme, and the kinetic parameters of the immobilized bromelain were analyzed. (C) 2017 Elsevier Ltd. All rights reserved.