Chromatic Sensor to Determine Oxygen Presence for Applications in Intelligent Packaging

Abstract

A chromatic sensor has been designed for the detection of oxygen in package headspace. The sensor is based on the redox change of methylene blue (MB) to its leuco form. Its formulation includes the pigment, glycerol, as a sacrificial electron donor, TiO2, as a photocatalyst and ethylene-vinyl alcohol copolymer (EVOH), as a structural polymer matrix. The final sensor design that allows its manufacture by conventional printing and laminating technologies consists of the sensing polymer matrix (MB-EVOH) sandwiched in a suitable transparent multilayer structure. The outer layers protect the sensor from the external atmosphere and allow visualization of the colour. The inner layer is sufficiently opaque to facilitate sensor reading from the outside, is thick enough to avoid direct contact with food (functional barrier), and is oxygen-permeable to expose the sensing material to the internal package atmosphere. In the absence of oxygen, the sensor becomes white by irradiation with halogen lamps in less than 60 s. All components are substances permitted for food contact except the pigment, but specific migration analysis showed no trace of migration thanks to the functional barrier included in the design.

Inkjet-printed O2 gas sensors in intelligent packaging

“…Its blue colour in air becomes colourless in the absence of oxygen. 11 A considerable variety of this type of sensor has been developed, all based on a redox dye, typically methylene blue (MB), a sacrificial electron donor (SED) and a UV light sensitive semiconductor photocatalyst (SC), all encapsulated within a polymer. [12][13][14][15][16][17][18][19] When the sensor is exposed to UV light, electrons are promoted from the valence to the conduction band within the SC to create electron hole pairs.…”

Smart Food Packaging Designed by Nanotechnological and Drug Delivery Approaches

“…Ethylene-vinyl alcohol copolymer loaded with methylene blue can be used for monitoring the oxygen presence, as described by Lopez-Carballo et al [134]. In this regard, the chromatic sensor can be manufactured by conventional printing and lamination technology.…”

“…There are also many other ways of visualizing such as that proposed by Kim et al [134] who used the Cannizzaro reaction in order to induce color change from yellow to orange and then to red due to the specific reactions of the evolved aldehydes.…”

“…Color change from blue to red can be achieved as a consequence of extreme processing/storage conditions (pH and temperature) [133] Ethylene-Vinyl Alcohol copolymer methylene blue Oxygen sensor based on methylene blue ⇔ its leuco form [134] Chitosan gold nanoparticles…”

Smart and Safe packaging

“…Photoluminescent dyes are usually made of ruthenium or platinum complexes often substituted with porphyrin ligands. The active material is often immobilised inside the packaging in the form of a label 284,[286][287][288][289][290][291][292] , by coating directly on the packaging itself 293,294 , or by incorporating inside the packaging film 285 (Figure I-22). The quality of food products at the point of sale such as meat, cheese or salad can be detected using this sensor type.…”