ReviewCarbon dioxide sensors for intelligent food packaging applications

Recently, the demand for safe and high quality foods, as well as changes in consumer preferences have led to the development of innovative and novel approaches in food packaging technology. One such development is the smart or intelligent food packaging technology. Intelligent packaging has enabled to monitor and communicate information about food quality. This technology also helps to trace a product's history through the critical points in the food supply chain. In general, occurrence of elevated CO2 gas level is the prime indicator of food spoilage in packed foods and also its maintenance at optimal levels is essential to avoid spoilage in foods packed under modified-atmosphere packaging (MAP) conditions. Hence, a CO2 sensor incorporated into food package can efficiently monitor product quality until it reaches the consumer. Although much progress has been made so far in the development of sensors monitoring CO2, most of them are not versatile for food packaging applications and suffers from limitations such as high equipment cost, bulkiness, and energy input requirement, including safety concerns. Therefore, the development of efficient CO2 sensors that can intelligently monitors the gas concentration changes inside a food package and specific to food packaging applications is essential. In the present review, progress on the development of different types of CO2 sensors such as optical sensors, polymer opal films, polymer hydrogels, etc., which can be readily applicable to food packaging applications, is discussed.