Evaluation of an 'After Opening Freshness (AOF)' label for Packaged Ham

A new type of commercial time-temperature indicator, TTI, namely the ‘After Opening Freshness Label’, i.e. AOF label, is evaluated. The label comprises a plastic film colorimetric CO2indicator layer encapsulated in a polymer sheath, the permeability of which controls the rate of diffusion of the CO2 in to and out of the indicator film. The CO2 sensitive indicator film inside the label is relatively fast in responding (recovering its original colour in 26 min at 25 °C) when the ambient atmosphere is changed from that of the MAPed package (containing 25% CO2) to air, but when encapsulated in the polymer sheath used in the AOF label, which uses polyethylene terephthalate, PET, as a gas diffusion barrier, under the same conditions its recovery time is ca. 30 h (at 25 °C). Key to its commercial function – as a consume within indicator – at 5 °C, the label’s recovery time is ca. 96 h (i.e. 4 days). While UV/Vis spectrophotometry is used to characterise the optically transparent CO2indicator, photography, coupled with digital image colour analysis is used to characterise the AOF label. A study of the kinetics of colour recovery of the AOF label as a function of temperature revealed an activation energy, Ea, of colour recovery of ca. 43 kJ mol−1, which is similar to a number of different food spoilage processes. The potential of the AOF label as a ‘consume within’ indicator to help minimise the large amount of unnecessary household food waste associated with many developed countries is discussed briefly.