Abstract: The effect of monochromatic light on the oxidation of lipid and myoglobin in raw ready-to-eat tuna was studied for optimizing the lighting condition during display. Tuna akami samples were illuminated by light-emitting diode (LED) lamps with four different monochromatic lights (red, yellow, green and blue) under three different modes, i.e., the same power, the same light intensity, and gradient light intensities. Changes in thiobarbituric acid reactive substances (TBARS) value and methemoglobin content in tuna akami muscle during subsequent storage were measured. The results showed that monochromatic light significantly promoted lipid oxidation and accelerated myoglobin oxidation in tuna samples compared with dark conditions during storage. At the same light intensity, this effect increased with decreasing wavelength, but yellow light was less effective than red light; there was also dependence upon light intensity, especially for blue and green lights in comparison with yellow and red lights. Furthermore, both lipid and myoglobin oxidation followed a zero-order kinetic equation. Therefore, red and yellow lights with long wavelengths rather than green and blue lights with short wavelengths are recommended for raw ready-to-eat tuna products during display.

Key words: tuna, illumination, lipid oxidation, metmyoglobin, kinetic model