Abstract: Bacterial cellulose-tea polyphenol composite films were prepared by soaking bacterial cellulose hydrogel in tea polyphenol solution and then thermally drying it. The optimization of tea polyphenol concentration and soaking time was done based on the antimicrobial activity, mechanical properties, light transmittance, water absorption, water vapor permeability and structure of bacterial cellulose-tea polyphenol composite films. Our aim was to obtain composite films with strong antibacterial activity and good flexibility. The results showed that the concentration of tea polyphenols was positively correlated with the antibacterial ability of the composite films. When tea polyphenol concentration was greater than 0.2%, the inhibition zone diameter was significantly changed (P < 0.05), indicating strong antimicrobial activity. With increasing concentration of tea polyphenols, the tensile strength, light transmittance, water absorption and water vapor transmission rate declined gradually, while the elongation at break, thickness and flexibility increased. To cut down the cost of the composite film and at the same time not to affect its quality, the optimum concentration of tea polyphenols was determined to be 0.2%. All the parameters of the composite film changed with soaking time similarly as with tea polyphenol concentration; they did not change significantly (P > 0.05) when soaking time exceeded 4 h. Four hours was therefore selected as the optimal soaking time. The cellulose-tea polyphenol composite film had a characteristic absorption peak of bacterial cellulose. Compared with the pure film, the composite film was more compact, closely linking tea polyphenols to bacterial cellulose molecules.

Key words: bacterial cellulose, tea polyphenols, film properties, film structure