An intelligent indicator for warning of short‐term high CO2 damage to garlic scapes

Abstract A pH‐sensitive indicator film based on CO 2 change was prepared by mixing a water‐soluble indicator (bromocresol green and chlorophenol red sodium) with a film‐forming carrier (methyl cellulose (MC), polyvinyl alcohol (PVA) and glycerin). The innovation is not only to analyse the response characteristics of the colorimetric indicator to CO 2 , but also to optimise the preparation parameters of the film. The response experiment showed that CO 2 dissolved rapidly in water and the pH value remained unchanged after reaching equilibrium, with a one‐to‐one relationship between pH and CO 2 concentration. As the CO 2 concentration rose from 18% to 20%, the colour of the indicator film changed from blue–purple to yellow–green in a different colour space, allowing the change to be easily distinguished by the naked eye. The optimum parameters (13 g‧L −1 MC, 5 g‧L −1 PVA, 10 g‧L −1 glycerin, 15 ml‧L −1 indicator and a casting amount of 0.2 ml‧cm −2 ) for preparing the intelligent film were optimised based on puncture strength (PS), water vapour permeability (WVP), water solubility (WS), casting time (CT) and colour performance. Evaluating this application using garlic scapes stored at 15°C revealed that the total colour difference was 34.23 as the CO 2 concentration increased from 18.7% to 20.4%, and the colour of the indicator film changed from blue–purple to yellow–green. Therefore, the intelligent packaging film was able to effectively provide a warning when garlic scapes were exposed to damage from a short‐term high CO 2 level.