Fluorescent Sensor for Visual Monitoring of High-Protein Food Freshness

This report indicates that in the future, determining whether a steak is fresh may not require opening the packaging; a glance at the smart label on the package could suffice. Recently, the Institute of Bast Fiber Crops of the Chinese Academy of Agricultural Sciences successfully developed a new type of fluorescent sensor that can be firmly attached to food packaging like a “band-aid”. This sensor can accurately monitor and display the freshness levels of high-protein foods such as shrimp, fish, and beef, even in humid environments. This innovative research, which provides a new solution to the problem of food waste, has been published in the Chemical Engineering Journal.

Approximately one-third of food produced globally is wasted during production, transportation, storage, and consumption. In daily life, consumers often discard food that is in a “sub-fresh” state, which is still safe to eat, because they cannot accurately assess the true freshness of meat and fish inside the packaging. In recent years, many intelligent monitoring systems based on flexible hydrogel integrated with ammonia-responsive materials have emerged, achieving dynamic monitoring of food freshness. However, existing research generally overlooks the challenges posed by high-humidity storage environments—food spoilage can lead to a decrease in cellular water retention, tissue fluid exudation, and increased environmental humidity. The food’s own moisture content, temperature fluctuations, and microbial activity can also cause humidity to rise, while high humidity can cause hydrogel structures to collapse and traditional adhesives to lose their stickiness, rendering monitoring systems ineffective. Furthermore, traditional hydrophilic acrylic pressure-sensitive adhesives are prone to adhesion failure in long-term high-humidity environments, preventing conventional tapes from providing stable support for monitoring systems, thus limiting their commercial application. Therefore, it is crucial to develop intelligent monitoring systems that possess moisture-proof characteristics and direct adhesion capabilities.

The research team combined lipoic acid derivatives with fluorescent molecular partners to design a fluorescent sensor with self-adhesiveness, environmental tolerance, and biological amine responsiveness through a simple one-step thermal pressing strategy. This uniquely designed molecular structure allows the sensor to adhere firmly to various packaging substrates without the need for additional adhesives. Notably, this fluorescent sensor exhibits excellent adhesion performance on common food packaging materials, allowing for direct attachment and freshness monitoring even in harsh storage environments with low ammonia, high salt, high humidity, or underwater conditions, without the need for commercial tape, providing a new strategy for in-situ visual monitoring of high-protein foods.

Researchers state that this technology is akin to applying a “smart band-aid” to food packaging, providing significant technical support for reducing food waste. The sensor has been successfully applied in freshness monitoring experiments for various high-protein foods such as shrimp, fish, beef, and pork, demonstrating excellent performance and offering a new technical pathway for intelligent judgment of food shelf life in the future.

See more in the China Food News (November 6, 2025, Page 7)

Typesetting and design: Lin Qian

Review: Ouyang Meihua

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