# Intelligent Packaging for Real-Time Monitoring of Food-Quality: Current and Future Developments
## 4 Future Perspectives and Concluding Remarks  
Nowadays, the market for active, intelligent, and smart food packaging is rapidly increasing with more than USD 38 billion worth of packages being sold in 2020 and about USD 50 billion expected by 2026 [177]. However, such systems are still scarcely applied due to their high cost compared to traditional packaging materials and the limited possibility of integration within the existing packages [178; 179; 180]. In this sense, the recent developments in chemistry, microelectronics, materials science, engineering, biotechnology, and nanotechnology may help in the design and fabrication of efficient, novel packaging solutions suitable for large-scale applications. For instance, food quality optical detection systems based on colorimetric sensors display great potential to overcome the current challenges, including the high cost and the requirement of sophisticated instruments. Such systems may, indeed, provide a simple and easily readable indication concerning food quality over a long time period. Additionally, the sensitivity of such colorimetric devices and sensors may be even enhanced by integrating them with an RFID, aiming to achieve improved safety and quality, while reducing food waste and limiting costs [181; 182; 183; 184]. Specifically, on one side, colorimetric systems allow for easy read-out by any kind of user, including the consumers. On the other, the continuous advances in printed electronics via the deposition of conductive inks on various substrates are expected to favor the integration of intelligent sensors in packaging materials [185; 186]. Nevertheless, it is noteworthy that the lack of standardized and comprehensive toxicity evaluation methods, as well as the often limited stability of the so far developed sensors that could generate the migration of substances in the food products, has generated confused and frequently inconsistent data as far as health and safety concerns are considered. Thus, this poses a  
Figure 6: (**a**) Picture of a hybrid plasmonic-photonic crystal and (**b**) sketch of the multilayered structure. (**c**) Optical transmittance before (green) and after exposure to _E. coli_ (blue line). Reproduced with permission from [172]. Copyright © 2019, American Chemical Society. challenge in the large-scale fabrication and use of intelligent packages [187, 188]. Hence, the development and validation of standardized tests concerning the safety of future intelligent packages represents one of the main issues to be addressed before their effective large-scale usability. Moreover, it is critical to ensure that intelligent packaging is sustainable in terms of application, design, and production [189, 190, 191, 192]. This is vital not only to improve the management of the food supply chain, but also to reduce global food waste and environmental pollution [27, 193]. Specifically, the growing environmental burden related to petroleum-derived plastics imposes the enrichment of packaging products with eco-friendly features. However, to date, intelligent devices such as colorimetric and optical tags and especially RFDI and sensors are often not yet designed in respect of recyclability and/or sustainability mechanisms, since their main purpose is to improve food shelf-life by being as cheap and functional as possible. Hence, naturally occurring polymers based on renewable resources, such as cellulose and chitosan, may represents considerable areas of innovation and exciting opportunities for the inexpensive, safe, and sustainable fabrication of eco-friendly intelligent packaging materials. In conclusion, this review critically discusses the most common optical approaches and emerging technologies for real-time food monitoring and addresses topics related to their future development for large-scale food packaging applications. These are usually based on different types of food quality indicators (i.e., pH, O\({}_{2}\), CO\({}_{2}\), temperature, etc.) and can provide information for consumers as regards product safety.