Both the waste of edible food and the consumption of non-edible food within the best before date are ongoing concerns in food industry. Until now, no methods are applied to access food quality of packed food without opening of packages. We demonstrate the formulation of a sensor foil comprising of a non-toxic porphyrin on an inorganic matrix in polyethylene. The sensor foil is capable of detecting amines in the gas phase over food products, which could act as spoilage indicators during the shelf life of packaged food. The foil was optimized to prevent reactions with other analytes in the gas phase of food by the alteration of the hydrophobic polymer. We performed experiments, using model packing units, to monitor the behavior of the foil and correlated the change in the fluorescence spectra to the total viable count of bacteria on the fish. The readout of the foils was performed with fluorescence spectroscopy to yield highly accurate results in contrast to less accurate the colorimetric determination.
Along food supply chains, several critical steps can lead to inconsumable food. Especially food of animal origin undergoes rapid aging, when stored inadequately. Quality assessment of packaged food products faces serious problems ranging from the loss of integrity of the package to damage of the food and it is applied only to a low number of samples per batch. As a result, food products are either wasted or not analyzed, which results in a significant decrease in food safety. As a part of an intelligent packaging system, we designed a sensor foil that can detect amines, produced during the food aging process. Change of the fluorescence of the sensor foil can be assessed with spectroscopy or color change from green to red can be detected optically with a camera, e.g. by smartphone. The foil can be incorporated inside the single packaging units and noninvasively measured routinely by the store or consumer. The readout of the foils was performed with steady-state tabletop spectrometers, which were then compared to the results for readouts with different inexpensive handheld devices that could be used during real-life applications, e.g., at any step in a food supply chain. Ideally, the single food product is linked to a single foil at the primary producer, measuring the first spectrum and connecting the data to the specific product, e.g. via distributed ledger. For a transparent process chain, QR-codes could be utilized to allow access to the freshness data along the shelf life of a single package.
Food waste during all stages of the supply chain and at the consumer is an emerging problem. Non-destructive methods to determine the freshness of packaged food products could play an important role in the reduction of this problem. In this study, we developed a chemical sensor, i.e. a sensor foil, capable of detecting amines as food spoilage indicators in reaction vessels and model packaging units by fluorescence spectroscopy. To obtain the foil, a phosphorylated porphyrin was adsorbed to silica and then extruded in polyethylene. The reactivity of the foil was tested with single amines in reaction vessels to demonstrate the behavior under ideal conditions. The sensor foil was applied in model packages containing salmon or cheese to show that fluorescence spectroscopy can be used to detect the emission of spoilage indicators. Lastly, model experiments with cod filets were carried out to obtain data to test the capability of determining the freshness by machine learning algorithms.
A central challenge in the treatment of different diseases is the delivery of therapeutic agents to a specific cellular site. Liposomes that can release their cargo upon an externally controlled trigger are attractive candidates for localized drug release. Light as external trigger can be controlled temporal and spatial with high precision. In this study, we investigate the potential of light sensitive liposomes with four different photosensitizers for light-induced release. To demonstrate permeabilization of the liposomes, we encapsulated calcein in high concentration inside liposomes, that calcein fluorescence is quenched. If calcein is released from the liposome, quenching is diminished and the fluorescence increases. We demonstrated that liposomes with the sensitizers Benzoporphyrine derivative monoacid (BPD), chlorine e6 (Ce6), Al(III) Phthalocyanine chloride disulfonic acid (AlPcS2) and a di-hydroxyphenyl porphyrine (5,10-DiOH) release cargo effectively after irradiation. Liposomes with 5,10-DiOH showed a quicker release compared to the other sensitizers. Further we observed through fractionated irradiation, that most of the release took place during light irradiation, while the permeability of the liposome decreased shortly after light exposure.
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