Photo Sensitivity of Fresh Meat Color in the Visible Spectrum

SUMMARY –The effect of specific wavelengths of visible light on fresh meat color was investigated. 2‐in. diam cores of meat were aseptically prepared from top rounds (adductor muscle and semimembranosus muscle). Freshly oxygenated face‐to‐face cuts were used as the sample and control. The sample and control were packaged in mylar polyethylene pouches and cooled moist filtered air was circulated through the pouch for the duration of the experiment. Samples were exposed to the following wavelengths at an energy level of 0.5 mw/cm 2 : 420.0, 510.0, 550.0, 570.0, 590.0 and 632.8 nm. Experiments were conducted at 34°± 1°F and 41°± 1°F for 2 and 5 days of exposure. The controls were next to the sample but kept in darkness during the exposure period. There was no temperature differential between the sample and control. Oxidized heme pigment content was determined by reflectance spectrophotometry. No wavelength enhanced the formation of oxidized heme pigment more than any other, however illuminated samples contained an average of 5.5% more oxidized heme pigment than did the controls. Oxidized heme pigment content increased with lengthened storage time and increased temperature. The increase in oxidized heme pigment content as a result of illumination may be due to a photochemical activation of a compound such as riboflavin which then may react with oxygenated heme pigments to form oxidized heme pigments.