In many cases, food deterioration is caused by oxida-
tion of food constituents or spoilage by moulds in the
presence of O2. Although O2-sensitive foods can be
packaged appropriately using modi®ed atmosphere
packaging (MAP) or vacuum packaging, these tech-
nologies do not always remove O2 completely. Moreover,
the O2 that permeates through the packaging ®lm
cannot be removed by these techniques.