Iridescent chitosan membrane as a colorimetric sensor for visual detection of lipid oxidation

Iridescent CSM is obtained from shrimp shell by deproteinization, demineralization and deacetylation. • Iridescent CSM is a mesoporous material with Bouligand structure. • CSM exhibited chromatic responsiveness toward aldehydes, ketones and acids. • CSM successfully identified all highly oxidized samples through noticeable color changes. Lipid oxidation is a major cause of food deterioration and can be detected visually using colorimetric sensors. However, existing sensors often involve the use of harmful chemicals or dyes. This study aimed to exploit the potential of structurally colored biomaterials as lipid oxidation sensors. An iridescent chitosan membrane (CSM) with structural color was fabricated from shrimp shells by chemical deproteinization, demineralization and deacetylation. Its responsiveness toward 28 volatile lipid oxidation products was investigated, and its effectiveness as a lipid oxidation sensor was evaluated. The results showed that the CSM exhibited a Bouligand structure. The membrane had a deacetylation degree of 83.97%, a specific surface area of 0.30 m 2 /g, an average pore volume of 0.0006 cm 3 /g, and an average pore diameter of 8.76 nm. It showed visible color changes upon exposure to aldehydes, ketones, and organic acids, with minimum visually discernible concentrations of 14 μmol/L for organic acid, 54 μmol/L for aldehydes and 1085 μmol/L for ketones. Moreover, CSM exhibited excellent structural stability and remained chemo-responsive during one year of storage under room temperature conditions. Eight soybean oil samples derived from the same oil but at different oxidation stages were used for assessing the performance of CSM as a lipid oxidation sensor. Out of the eight oil samples, the CSM correctly identified the oxidation status of seven, showing no color change for fresh samples and visible color changes for oxidized ones. This work demonstrates the potential of the structurally colored CSM as a biocompatible and chemical-free colorimetric indicator for lipid oxidation detection. Download: Download high-res image (225KB) Download: Download full-size image