Alginate/chitosan bi-layer hydrogel as a novel tea bag with in-cup decaffeination

In this study, the environmental concerns of current tea bags as well as in-cup decaffeination are addressed with the synthesis of efficient and biodegradable bi-layered, alginate-chitosan hydrogel tea bag (D-HTB). A simple, environmentally friendly synthesis method was employed to prepare the novel hydrogel tea bag. D-HTB was prepared by tea encapsulation in an alginate matrix, and activated carbon was decorated in another chitosan layer for decaffeination using a facile directional freezing and crosslinking technique. The microstructural and thermal properties of the prepared tea bags were studied using a digital microscope (DM), field emission scanning electron microscope (FE-SEM), and thermogravimetric analysis (TGA). Directional ice freezing created lamellar increasing the surface area, which resulted in excellent tea release efficiency and decaffeination. The release kinetic profile was investigated, and the data fit well to the Korsmeyer-Peppas model indicating Fickian diffusion-controlled tea release. The as-prepared D-HTB shows a maximum release efficiency of 92.5% polyphenols and decaffeination of ~40% compared to that of the commercial tea bag. Thus, D-HTB has an excellent potential of being an environmentally-safe and in-cup decaffeination alternative to the current tea bags.