The shelf life of food is of great concern to food safety. This paper reports a cost-efficient integrated QR code label with dual sensing and information storage functions by printing technology, which can be applied to predict the shelf life of food products at different temperatures effectively. The QR code label includes the thermochromic zone and freshness sensing zone, which prepared by thermochromic ink and freshness sensing ink with inkjet printing and screen-printing techniques, respectively. The temperature-dependent color difference of the thermochromic zone under an external light source is obtained with a linear rescaling method. The sensitivity and reversibility of the thermochromic zone is analyzed as well, respectively. The results show that the thermochromic zone prepared by water-based ink with 18% mass fraction of thermochromic microcapsule powder has a high sensitivity, good linearity and reversibility, which can be used for real-time monitoring of temperature. Similarly, the freshness sensing zone is realized by a mixture of anthocyanin and curcumin inks with inkjet printing technique. The integrated QR code label is applied for the quality evaluation of the freshness of grass carp at 4 °C, which can effectively display the real-time temperature, freshness and the origin of food products of grass carp simultaneously, providing new ideas for the application of QR code label in smart packaging.

Graphical Abstract