Estimation of color changes in fish surface at the beginning of grilling based on the degree of protein denaturation

• At the beginning of grilling L* value increased along with protein denaturation.
• Kinetics parameters of the reduction rate of protein denaturation of red sea bream were obtained.
• Calculated L* values were estimated with the contributions of myosin and actin.
• Empirical equations for estimating a* and b* values were obtained from calculated L* values.

Color changes at the beginning of grilling were estimated from protein denaturation. Samples of red sea bream (Pagrus major) were grilled under far-infrared radiation heating. The temperature and color (CIE L*, a*, and b* values) of the surface of the samples were monitored over time. Protein denaturation was evaluated by differential scanning calorimetry. Two peaks, which were regarded as denaturation of myosin and actin, were observed. Kinetic parameters (Ea and Z) were calculated using the dynamic method with five heating rates (8, 10, 13, 17, and 20 °C min−1). Measured L* value increased as protein denaturation progressed in the first 2 min of grilling. The total non-denaturation ratio using the contributions of 0.70 and 0.30 of myosin and actin, respectively is regarded as the best fit to the changes of L*. Empirical equations for estimating a* and b* values were deduced based on calculated L* values and gave good approximations to the measured ones.