A review on colorimetric indicators for monitoring product freshness in intelligent food packaging: Indicator dyes, preparation methods, and applications

Abstract

Intelligent food packaging system exhibits enhanced communication function by providing dynamic product information to various stakeholders (e.g., consumers, retailers, distributors) in the supply chain. One example of intelligent packaging involves the use of colorimetric indicators, which when subjected to external stimuli (e.g., moisture, gas/vapor, electromagnetic radiation, temperature), display discernable color changes that can be correlated with real‐time changes in product quality. This type of interactive packaging system allows continuous monitoring of product freshness during transportation, distribution, storage, and marketing phases. This review summarizes the colorimetric indicator technologies for intelligent packaging systems, emphasizing on the types of indicator dyes, preparation methods, applications in different food products, and future considerations. Both food and nonfood indicator materials integrated into various carriers (e.g., paper‐based substrates, polymer films, electrospun fibers, and nanoparticles) with material properties optimized for specific applications are discussed, targeting perishable products, such as fresh meat and fishery products. Colorimetric indicators can supplement the traditional “Best Before” date label by providing real‐time product quality information to the consumers and retailers, thereby not only ensuring product safety, but also promising in reducing food waste. Successful scale‐up of these intelligent packaging technologies to the industrial level must consider issues related to regulatory approval, consumer acceptance, cost‐effectiveness, and product compatibility.

Genipin-Crosslinked Gelatin/Chitosan-Based Functional Films Incorporated with Rosemary Essential Oil and Quercetin

“…In today’s food packaging field, there is an increasing trend to replace non-degradable plastic packaging materials using annually renewable natural biopolymers to solve the problems of environmental pollution and resource depletion caused by the use of synthetic plastics [ 1 , 2 ]. Biopolymer-based food packaging materials are environmentally friendly, biocompatible, and even edible without any safety concerns [ 3 , 4 ].…”

Shikonin Functionalized Packaging Film for Monitoring the Freshness of Shrimp

“…Active packaging is useful to enhance the shelf-life of food products, whereas intelligent packaging can sense and monitor the quality of the food during storage [ 1 , 2 ]. In intelligent packaging, the colorimetric process is the simplest, and it can perceive visual changes in food during spoilage in real-time [ 3 , 4 ]. The food quality changes during storage are subjected to the formation of ethylene, carbon dioxide, and other volatile gases, as well as microbial attacks and oxidation [ 5 , 6 ].…”

Active modulation of reflective structural colors

“…The operational principles in these alternative display technologies may also be used in smart color labels, where a colored state changes in response to external stimuli such as humidity, gas, light, etc. Owing to the ability to convey information intuitively through simple color variations, reflective colorimetric labels find use in a wide range of areas including hazard detection, 3 food quality monitoring, [4][5][6][7][8] air quality evaluation, 9 etc.…”