Spectral Studies on the Role of Ionizing Radiation in Color Changes of Radappertized Beef

Abstract

iron, which alters it from a ferric to a ferrous state.Effects of ionizing radiation on beef pigments were studied by determining the absorption spectra of myoglobin solutions and the reflectance spectra of radiation-sterilized beef slices. Bovine and ovine oxymyoglobin (MbO,) and met(ferri)myoglobin (metMb) were extracted, purified, and treated with gamma radiation. Increasing dose and temperature of gamma radiation produced increasing shifts in characteristic peaks and progressive decreases in the Soret bands of these pigments. The total color difference (AE), computed from tri-stimulus values of reflectance spectra of radiation-sterilized beef, showed similar dependence of color on radiation dose and temperature. Re-irradiation of beef allowed to brown in air caused the unstable red pigment to re-form. The presence of oxygen in the container during radiation-sterilization reduced the red color formation. The results show that ionizing radiation reduces the heme iron of the brown pigment of cooked meat (globin myohemichromogen) to an unstable red pigment (globin myohemocbromogen), which, upon exposure to air, reverts to the original ferric (brown) pigment.Clark and Richards (197 1) reported that gamma irradiation of beef metMb with 1 Mrad changes it to a compound that has characteristic absorption peaks at 542 and 582 nm and a Soret band at 411 nm. These authors suggested that a chole-heme protein is formed by rupture of the hemin nucleus, which is still principally attached to the denatured globin.Richards and Morrison (1971), who studied color changes in beef exposed to pasteurizing doses of gamma rays, showed that irradiation of samples packaged in oxygen-permeable film produced less red color than irradiation of comparable samples packaged in oxygen-impermeable film. Giddings and Markakis (1972) suggested that there are two myoglobin derivatives produced by gamma irradiation of ferrimyoglobin solutions. When the solution is anoxic before irradiation, a reductive oxygenation (via hydrated electrons from water radiolysis) to Mb02 takes place. In solutions containing oyxgen, ferrylmyoglobin (quadrivalent myoglobin) is generated via Hz OZ.

Porphyrin Metabolisms in Human Skin Commensal Propionibacterium acnes Bacteria: Potential Application to Monitor Human Radiation Risk

“…Recent research has shown that increasing dose and temperature of gamma radiation can produce increasing shifts in characteristic peaks and significantly decreases in the Soret bands [31] Fig. (2).…”

Color Characteristics of Irradiated Vacuum‐Packaged Pork, Beef, and Turkey

“…Researchers have suggested that other pigments are formed as a result of irradiation. Kamarei et al (1979) suggested that the shift in color in cooked beef was caused by an oxidation/reduction reaction, where irradiation caused the reduction of oxidized globin myohaemichromagen to reduced globin myoheamochromogen. They also suggested that the red compound in radiation-sterilized beef was dependent upon the heme group and not the protein moiety.…”

Radiation chemistry and the radiation preservation of food

“…Based on these and related results, the reduction of metMb in pre-cooked beef containing ~6 X 10~4 M metMb and irradiated at -40°C to 4 Mrads is estimated to amount to ~30%. Examination of reflectance spectra of pre-cooked beef indicates that upon irradiation the brown color converts to red, but upon subsequent exposure to light and air the color reverts to brown (12).…”