The effect of ionising radiation on the colour of beef, pork and lamb

The effect of irradiation (0 and 5 kGy) of beef, pork and lamb portions in retail overwrap packs and subsequent storage at 4°C was studied in relation to colour changes. The colour of the exterior surface of beef and pork was measured on the same samples on each day of storage for up to 7 days post irradiation. On day 7 the colour of a freshly cut surface was measured. The colour of both the exterior and a freshly cut surface of lamb, in similar retail overwrap packs was measured at 2, 5 and 7 days, post irradiation, different samples being used on each day of measurement. L* values of irradiated beef increased significantly with storage and a* values for unirradiated samples decreased significantly with storage. For lamb there was a general increase in L* and ho values and a decrease in a*, b* and C* values with storage. Analyses of the day 7 data showed statistically significant effects for species on all CIELAB parameters. Irradiation resulted in significantly higher hue angle (ho) values and the a*, b* and C* values were significantly higher on the exterior than freshly cut surface. There were a number of statistically significant 2 factor and 3 factor interactions. The role of formation of a carboxyhaem pigment in the colour of irradiated meat is discussed. The problem of interpretation of pigment changes from CIELAB values is highlighted.