Effect of drying temperature on microstructural, mechanical, and water barrier properties of konjac glucomannan/agar film produced at industrial scale
Jiaming Qin, Man Xiao, Shuangshuang Wang, Chun Peng, Xiaohe Wu, Fatang Jiang
Abstract
Konjac glucomannan (KGM)/agar blend films were obtained by casting at different drying temperatures (40 °C, 50 °C, 60 °C, 70 °C, and 80 °C) at an industrial scale. The effects of the drying temperature on the microstructure, mechanical, and water barrier properties of the films were investigated. The results showed that lower temperatures (40 °C, 50 °C, and 60 °C) led to enhanced H-bond interactions between KGM and agar and more ordered structures of KGM/agar films, as evidenced by FTIR and X-ray analysis. Correspondingly, the mechanical properties were altered with the film's structure and showed significant differences (p < 0.05) at various drying temperatures. Moreover, the drying temperatures from 40 °C to 80 °C had no significant influence (p > 0.05) on the water vapour permeability of the films. The film dried at 60 °C showed significantly higher water contact angle and lower swelling ratio and solubility than the other films. Additionally, the drying temperature of 60 °C gave the highest thermal degradation temperature. Therefore, 60 °C was recommended for KGM/agar film production. This research guides the selection of the optimal drying temperature for edible film production.