Developing an intelligent film containing Vitis amurensis husk extracts: The effects of pH value of the film-forming solution

Bio-based films have become preferred because of their biodegradability and availability from reproducible resources. Vitis amurensis husk is a byproduct of white-wine processing. The colors of Vitis amurensis husk extracts vary from red to green as the pH value increases from 2 to 12. A new bio-based intelligent colorimetric film was developed by incorporating Vitis amurensis husk extracts into the tara gum/cellulose matrix. The effects of pH value (3, 4, 5, 6, and 7) of the film-forming solution on the color, transparency, morphology, mechanical properties, barrier properties, and moisture uptake properties of the films were investigated. The color of the film changed from pink to yellow-green as the pH value of the film-forming solution increased from 3 to 7. The scanning electron microscope results showed that the cross sections of the film formed at pH of 3, 6 and 7 showed a wrinkled appearance. The reduction of the tensile strength and oxygen permeability were related to the wrinkle appearance. The resulting films changed in color after immersion in solutions with different pH values. Similar color changes occurred, and there was an apparent difference in the monitoring test for fish products. The film formed at pH 6 changed to green in 48 h, and the other film at pH 3, 4, and 5 changed in 60 h, indicating that it had a better sensitivity. This study showed that an intelligent colorimetric film can be utilized as a visual indicator for food quality assurance. (C) 2017 Elsevier Ltd. All rights reserved.