Novel indicators for food packaging

Abstract

This thesis details the development of two new types of colourimetric indicators for use in Modified Atmosphere Packaging (MAP).A new type of commercial time-temperature indicator (TTI) is evaluated. The C02-sensitive indicator film is relatively fast in responding when the ambient atmosphere is changed from that of the MAPed package 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). 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.A C02-sensitive, smart adhesive is reported in which a C02-sensitive pigment, comprising the pFI-sensitive dye, phenol red, PR, coated onto nano-particulate silica particles, is dispersed in a hot melt, pressure sensitive adhesive. A C02-sensitive, brightly coloured adhesive tape is produced by coating the smart adhesive onto a polymer 'barrier' film. When placed on the inside of 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 values of 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 by Insignia Technologies.

Date of Award	Dec 2019
Original language	English
Awarding Institution	Queen's University Belfast
Supervisor	Andrew Mills (Supervisor) & Amilra De Silva (Supervisor)