An eco-friendly film of pH-responsive indicators for smart packaging

Abstract

Red cabbage anthocyanin extract (RCAE) exhibited a higher pH sensitivity. This study aimed to develop a pH-responsive smart film based on modified cassava starch (acetylated distarch phosphate, ADSP) and RCAE. The morphological, structure, and chemical characteristics of smart films were examined using SEM, FTIR and XRD. The properties of films were measured in terms of swelling ratio, water vapor permeability, optical, and mechanical properties. When the RCAE concentration was not higher than 30%, the anthocyanins in the RCAE formed intermolecular hydrogen bonds and electrostatic interactions with ADSP, resulting in highly dense and cohesive films. The addition of RCAE improved the barrier properties and water-resistance of films. Moreover, the color response efficiency and color stability were also investigated. The RCAE content and the color intensity were positively correlated. NH 3 detection showed that the statistical function model (p < 0.01; R 2 = 0.94) for time and RCAE concentration fitted well with the test data. Considering that the developed film had good color stability and reversibility of color change, the film was suitable to be used in smart packaging. • Red cabbage anthocyanin extracts (RCAE) exhibited a higher pH sensitivity. • RCAE was anchored in films by hydrogen bonding and electrostatic interactions. • Storage time and temperature affected the color stability of the films. • The intelligent films exhibited an excellent color response to pH and NH 3 .