Novel aldehyde sensitive bio-based colorimetric film for kiwi fruit freshness monitoring

Abstract

The novel colorimetric film was designed to monitor the aldehyde emission from kiwi fruit based on ethyl cellulose/polyvinyl alcohol (EC/PVA) incorporated with poly (ethylene glycol) bis(3-aminopropyl) terminated (amine-PEG) and methyl red. The different colors of aldehyde-sensitive films were caused by a change in alkalinity, which was caused by nucleophilic addition reaction between aldehydes and amine-terminated polymers. The structure and basic properties (thermal stability, mechanical properties, hydrophobicity and barrier property) of the film were studied, as well as the colorimetric response of the film to aldehyde and its application in detecting of kiwi fruit freshness. Low incorporation of amine-PEG (no more than 2%) can improve the thermal stability and water vapor barrier of the films. When amine-PEG content was 2%, amine-PEG can be well distributed in the EC/PVA matrix by interaction of hydrogen bonding. As the kiwifruit ripened, the color of films changed from yellow to orange, and finally to red. The trends of color change in colorimetric film was similar with the changes of kiwi fruit freshness parameters, including sensory tests, TSS, hardness, weight loss rate, titratable acidity, ascorbic acid content and MDA. Therefore, the films can be used to real-time monitor the freshness of kiwi fruit during shelf life.