For dry food products, a different approach must be taken due to their low aw. Initiating the reaction can be done by incorporating photon dyes into the film. The photosensitive dyes will increase the reaction of the oxygen with iron compounds. This was a result of the discovery that iron will not react quickly enough with ground state oxygen to successfully extend shelf life. This exposure will catalyze the reaction to scavenge the free oxygen in the headspace of the package. The film is illuminated with UV light that will excite the dye molecules, which sensitize oxygen molecules that are diffused into the film, changing them to the singlet state. The singlet oxygen molecules react with acceptor molecules and are consumed (Nielsen, 1997).
The basic reaction for the use of photosensitive dyes to increase reaction rate of iron-based oxygen absorbers is shown in Figure 2 (Vermeiren, 1999).