A smart adhesive 'consume within' (CW) indicator for food packaging

A CO2-sensitive, smart adhesive is reported in which a CO2-sensitive pigment, comprising the pH-sensitive dye, phenol red, PR, coated onto nano-particulate silica particles, is dispersed in a hot melt, pressure sensitive adhesive. A CO2-sensitive, brightly coloured adhesive tape is produced by coating the smart adhesive onto a polymer 'barrier' film substrate. When placed inside on the plastic lidding of a CO2 MAPed package, the smart adhesive-based indicator changes to an orange/yellow colour due to the presence of the CO2, and returns to its original deep purple colour upon exposure to air, at a rate that depends upon temperature and the CO2 permeability and thickness of the polymer barrier film. The smart adhesive tape is used as a 'consume within', CW, indicator for refrigerated goods and briefly compared in performance to the more complex 'After Opening Freshness' indicator produced recently by Insignia Technologies Ltd. Other potential time-temperature applications of this new technology are discussed briefly.