Effect of light and packaging conditions on the colour stability of sliced ham.

The colour fading of sliced ham displayed in chill cabinets has been found to be caused by the combined action of light and oxygen, and can be prevented by a combination of packaging in a plastic material with low oxygen transmission rate (OTR<4 cm(3)/m(2)/24h/atm), a high initial vacuum level (>99%), and cold storage in the dark until residual oxygen in the packaging has been consumed (4 days for >99% initial vacuum). UV-light permeability of the packaging material had no effect on colour stability. The colour was measured by tristimulus colorimetric measurements on the surface of ham packaged in packaging material with different OTR (60 and <4 cm(3)/m(2)/24h/atm) and UV-light permeability (transparent above 360 and above 250 nm), and the change in colour was monitored by the Hunter a value, the tristimulus colorimetry parameter found (by analysis of variance) to give the best correlation with the subjectively evaluated ham colour. For each of the four types of packaging material, three different initial vacuum levels (85, 95 and >99%) were used.