Abstract
An inkjet printed membrane is presented as a colorimetric sensor for oxygen for use in smart packaging, in order to quickly inform the consumer about possible degradation reactions in modified atmosphere products (MAP). The colorimetric sensor is based on the redox dye, toluidine blue (TB), a sacrificial electron donor, glycerol, and, hydroxypropyl methylcellulose, as the hydrophilic polymeric matrix. The UVC-wavelength activated TB is photoreduced by SnO2 nanoparticle ink. This colorimetric oxygen indicator stays colourless upon exposure in nitrogen atmosphere to 7 min UVC light (6 W·cm-2). The photoreduced TB to leuco TB recovers its original colour upon exposure to oxygen for 55 min under ambient conditions (∼21 °C, ∼55%RH, 21% O2). The characteristics of the sensor have been evaluated, including its functionality through the colorimetric response to different oxygen concentrations as well as the influence of experimental variables such as humidity and temperature using a digital camera as the detector. The results obtained show that: (1) the colorimetric sensor remains stable in the absence of oxygen; (2) relative humidity greater than 60% significantly affects the reoxidation process; and (3) the temperature has a significant influence on the colour recovery, although the stability increases considerably when the sensor is kept refrigerated at 4 °C. A real application to packaged ham was performed, demonstrating that the printed colorimetric sensor is stable for at least 48 hours once activated and when the container deteriorates upon the entrance of oxygen, the sensor returns to its original blue colour, demonstrating its utility as a UVC-activated colorimetric oxygen sensor.
Highlights
Food companies are increasingly interested in controlling the shelf life of food to preserve the health of consumers and to reduce food waste
An inkjet-printed oxygen sensor was developed for use in smart packaging to quickly inform the consumer of the possible degradation reactions of packaged food in modified atmosphere (MAP)
The sensor is based on a redox dye toluidine blue (TB), a sacrificial electron donor, glycerol and hydroxypropyl methylcellulose as hydrophilic polymeric matrix and activated UVC
Summary
Food companies are increasingly interested in controlling the shelf life of food to preserve the health of consumers and to reduce food waste. Shelf life is the result of the relationship between food quality, consumer acceptability and packaging performance. For this reason, research in the field of food is currently very active, primarily in packaging, so as to help consumers make a more conscious and safer purchase. Intelligent packaging, which has the function of monitoring variations in the product and responding directly to them by changing a physical or chemical property. This has enormous potential to improve the safety, quality and traceability of food products, as well as increasing consumer
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