Colorimetric Food Freshness Indicators for Intelligent Packaging: Progress, Shortcomings, and Promising Solutions

Abstract

The colorimetric food freshness indicator (CFFI) is a promising technology in intelligent food packaging, offering the capability for real-time monitoring of food freshness through colorimetric changes. This technology holds significant promise in mitigating food waste and enhancing transparency across the supply chain. This paper provides a comprehensive review of the classification system for the CFFI, encompassing colorimetric films and sensor arrays. It explores their applications across key perishable food categories, including meats, seafoods, fruits, and vegetables. Furthermore, this paper offers an in-depth analysis of three critical challenges currently hindering technological advancement: safety concerns, stability issues, and limitations in sensitivity and selectivity. In addressing these challenges, this paper proposes forward-looking solutions and outlines potential research directions aimed at overcoming these bottlenecks, thereby fostering substantial progress in the development of this field.

Keywords: colorimetric; food freshness; food safety; freshness indicators; intelligent packaging.

Figure 2

(a) Colorimetric film for meats and seafoods freshness monitoring (i) fabrication of the film, (ii) color change of the film, and (iii) TVB-N and ΔE values when monitoring the freshness of beef, pork, salmon, and shrimp [33]; (b) colorimetric sensor arrays for meats freshness monitoring (i) fabrication of the sensor arrays, (ii) color change of the sensor arrays as the storage time of pork increases, and (iii) model establishment for TVB-N [48]. All the images are reproduced with permission from Elsevier.

Figure 3

(a) colorimetric film for fruits freshness monitoring (i) fabrication of the film, (ii) color change of the films with CO₂ concentration and FH, TSS changes of fresh-cut during storage, and (iii) correlation of films’ ΔE with FH and TSS of fresh-cut apples [57]; (b) colorimetric sensor arrays for vegetables freshness monitoring (i) color change of the sensor arrays as the storage time of three vegetables and (ii) DCNN model establishment for freshness prediction of three vegetables [80]. All the images are reproduced with permission from Elsevier.

Figure 1

Schematic representation of progress, shortcomings, and promising solutions of CFFI.

Figure 4

Leakage diagrams of the probes in a high-humidity environment with (a) hydrophilic polymers and hydrophilic/hydrophobic probes, (b) hydrophobic polymer and hydrophilic probes, and (c) hydrophobic polymers and hydrophobic probes.

Figure 5

The schematic diagram of anthocyanin degradation under UV light.