Controlled release of carvacrol and curcumin: bio-based food packaging by synergism action of TEMPO-oxidized cellulose nanocrystals and cyclodextrin

Oxidized cellulose nanocrystals with sodium carboxylate groups (TOCNC-COONa) and with free carboxyl groups (TOCN-COOH) were prepared and then chemically modified with beta-cyclodextrin (beta CD) and hydroxypropyl-beta-cyclodextrin (HP beta CD) to prepare materials able to load and release antibacterial molecules over a prolonged period of time. The materials were characterized by infrared spectroscopy, and the CD content of modified TOCNCs determined by phenolphthalein colorimetry. The extent of grafting was also assessed by QCM-D and microscopy was used to ascertain and compare the morphology of both TOCNC-COONa/HP beta CD and TOCNC-COOH/HP beta CD. Then, carvacrol and curcumin were entrapped by the attached HP beta CD and their prolonged release confirmed, as compared to neat material. The combined effects of HP beta CD and carvacrol on the antimicrobial properties of TOCNC-COOH films were finally evaluated.