Optical gas sensors in smart food bio-packaging: Innovation for monitoring the product freshness and safety

• Smart packaging monitors gas level for food quality. • Gas sensors detect carbon dioxide and ammonia as food deterioration indicators. • Indicator labels are suitable to evaluate and monitor the food freshness and quality. • The metrological characteristics are fundamental for the proper selection of sensors. • The metrological characteristics guarantee the monitoring reliability in the different operative conditions of smart food packaging. This paper will review food packaging gas sensors, emphasising their pivotal role in preventing food spoilage by detecting carbon dioxide, ammonia and other gases. When present above the levels established by national regulations, these gases are clear indicators of food spoilage, making sensors that detect them a fundamental tool for intelligent food packaging. As the demand for healthy, affordable, fast, and fresh foods continues to rise, the role of sensors in food packaging becomes increasingly crucial. Thus, sensors are crucial in early spoilage detection, preventing potential health risks and economic losses. Among the various types of sensors available, colourimetric sensors have been the most investigated. These sensors offer a straightforward yet effective method to monitor food quality, triggering visible colour changes in response to the presence of specific gases, providing a clear indication of food spoilage and instilling confidence in the safety of the food supply.