Influence of wavelength and packaging material on lipid oxidation and colour changes in low-fat mayonnaise

The influence of light of different wavelengths on lipid oxidation and colour changes in unpacked low-fat mayonnaise was studied using fluorescent light tubes emitting ultraviolet radiation and blue, yellow and red light. The protective effect of the polyester materials PET (polyethylene terephtalate). PEN (polyethylene naphtalate) and PET/PEN copolymer was evaluated by exposing mayonnaise packed in these materials to cool white fluorescent light. The change in colour of samples representing all storage conditions was almost entirely due to a decrease in yellowness, presumably as a result of photobleaching of beta-carotene, The colour was affected by wavelengths shorter than 470 nm with the greatest effect produced by wavelengths in the 410-450 nm range. The concentration of hexanal in the headspace was used as an indicator of lipid oxidation. The effect on lipid oxidation was most pronounced with ultraviolet radiation, although short wavelength visible light also had a significant effect. The polyester materials offered some protection against lipid oxidation by filtering out the ultraviolet radiation to varying degrees. PEN and PET/PEN copolymer offered better protection than PET. None of the materials offered sufficient protection against colour changes. (C) 2000 Academic Press.