Non-destructive and Rapid Method for Monitoring Fish Freshness of Grass Carp Based on Printable Colorimetric Paper Sensor in Modified Atmosphere Packaging

The freshness indicator can detect the freshness of food through characteristic color changes, and has the advantages of high accuracy and visualization. However, existing freshness indicators cannot achieve low-cost mass production. Addressing this challenge, a printed colorimetric freshness indicator which can be used into the modified atmosphere packaging (MAP) of grass carp for freshness monitoring is developed. A printable ink based on natural purple cabbage pigment, carboxymethyl cellulose, and glycerin was prepared, then it was printed in the paper by screen printing and applied to MAP. Additionally, the indicator labels were used in an application trial, which was conducted to monitor the freshness of grass carp under refrigeration (4°C) and at room temperature (25°C). The color response of freshness label was consistent with the spoilage threshold of total volatile basic nitrogen (TVB-N) and trimethylamine (TMA) content in fish sample. Therefore, the paper-sensor label can be used as a simple and practical indicator for freshness monitoring of grass carp.