Abstract
Globally, food waste has considerable economic and environmental consequences. Each year, a significant portion of food produced for human consumption is thrown away. The majority of this waste resulted from inefficiencies throughout the entire supply chain, leading to a degradation of food quality. Hence, reducing the degradation of food quality through the supply chain is of uttermost importance. Therefore, to achieve these objectives, it is imperative that effective and innovative packaging systems be developed that can be used to enhance and monitor food quality and extend the shelf life of food products, such as intelligent packaging and active packaging or smart packaging when both of them are connected into one single system. Nevertheless, the use of smart packaging in the context of monitoring the freshness and extending the shelf-life of food products is still at an early developmental stage, as it is limited by several technical constraints. (i) the intelligent packaging based on gas sensor still lack the selectivity towards a single target marker gas, (ii) the reported active packaging once put in contact with the food, starts releasing the encapsulated antioxidant in a continuous and noncontrolled manner, which means that the antioxidant is released although the food is still fresh, (iii) to the best of our knowledge all the reported intelligent and active packaging work in a discreet way and there´s no reported smart packaging system where the intelligent and active packaging work in a synergic approach. The solution to such issues requires the employment of an interdisciplinary approach, covering multiple research areas (i.e. sensing, and smart materials). The objective of this thesis focused on the development of a battery-free, stretchable, and autonomous smart packaging concept for extending the shelf-life of food products mainly meat, by integrating two different systems namely active packaging and intelligent packaging into one single system. This project involved a tri-fold approach consisting of: (i) development of a stretchable carbon nanotube gas sensor, (ii) development of an active packaging that releases an antioxidant in response to external stimuli, and (iii) integration of active and intelligent packaging into one single smart package. First and foremost, the need for improving the selectivity of the carbon nanotube gas sensor led to the development of an insilico technique based on machine learning, molecular dynamics simulation, and rational design for identifying new aptamers for ammonia. First, the performance of the selected aptamers was investigated in a liquid phase where an electrochemical aptasensor was developed. Afterward, we evaluated the performance of the aptamers in the gas phase. The reported ammonia gas sensor with enhanced selectivity was later on used as an intelligent package to measure the concentration of ammonia within the packaging in order to monitor the freshness of the food product. Secondly, technological advancements in the field of smart materials allowed the development of a versatile and on-demand active compounds delivery platform that can be used as active packaging. In this study, an on-demand active compound delivery platform was developed, consisting of flexible electrospun polypropylene carbonate (PPC) fibers infused with cinnamon essential oil (CEO), and coated with PEDOT:PSS and PNIPAM for enhanced conductivity. Moreover, the device was capable of switching reversibly between hydrophilicity and hydrophobicity below and above the lower critical solution temperature (LCST). In this manner, the device demonstrated a controlled release of bioactive compounds above the LCST value. Additionally, a PEDOT:PSS layer was incorporated into the device, enabling it to function as an electrically conductive device. When a suitable voltage was applied, its temperature increased in a controlled and measurable manner. Additionally, the PNIPAM layer served as a barrier that prevented the release of essential oil whenever it was not needed, and it permitted the release of oil when the device exceeded 32 °C and an appropriate voltage was applied. Thirdly, the two developed packagings namely active and intelligent packaging were integrated into one single system. This system is named smart packaging which it had the ability to monitor the freshness of the food product and once the food starts to get spoiled it triggers the release of antioxidants. The reported smart packaging works in a closed-loop and wirelessly thanks to the integration of the Near-field communication (NFC) chip and antenna. The smart packaging harvests energy from an NFC reader. In the absence of ammonia inside the headspace of the food packaging “meaning the food is fresh” the harvested energy is very low to power the heater implemented inside the active packaging to trigger the release of the antioxidant. In contrast, in the presence of ammonia “meaning the food is starting to get spoiled” the harvested energy increases thereby triggering the release of antioxidants.