Dynamic Colour Changes Depending on the Temperature Inside the Final Beef Product in a Process of Frying and Grilling

Four different beef muscles (PM, SM, LTL, TB) were examined. These muscles were fried or grilled. Each muscle was observed at various internal temperatures: 60°C, 65°C, 70°C, and 75°C. At each temperature level, a measurement of colour was taken using a Minolta Chroma Meter CR-400 in a L*a*b* system. The values of the parameters L*, a*, and b* were measured on a cross-section sample (two areas) after cutting perpendicular to the fibres at the middle of its height. Area I was located at the central part of the steak with a diameter of 2 cm. Area II was located at a distance of 1 cm from the edge of the steak. From the results obtained, the difference in colour values between areas was noted. The results indicated that area I was lighter and redder in comparison to area II. The values of parameters L* and a* recorded in the first area were higher in comparison with the values from the second region, indicating that the sample in the area I was lighter and redder than in the area II at the outside of the sample. There was a large variation in the colour of the two areas. It was observed that for all sampled fried muscles, the highest difference in lightness (ΔL*) between the two test areas was obtained at a heat treatment temperature of T_i= 65°C inside the sample. With grilling the highest value for overall difference in colour between areas was from samples heated to a final temperature of T_i=60 °C.