Analysis of pigments in intact beef samples: A simple method for the determination of oxymyoglobin and ferric myoglobin in intact beef samples using reflectance spectrophotometry

Abstract
Summary: Some basic aspects of the determination of the relative proportions of myoglobin pigments in meat by reflectance spectrophotometry are briefly reviewed. The potential of the Unicam SP 890 diffuse reflectance accessory for the quantitative determination of myoglobin forms in beef is assessed. The construction of the Unicam apparatus differs from most other reflectance units in that it has no integration sphere. The K/S values obtained with the Unicam apparatus and the requirements to be met by the samples correlate well with those for other spectrophotometric apparatus, except that the thickness of meat samples does not seem to affect the measured reflectance.A simple and rapid method is described for the determination by reflectance spectrophotometry of the proportion of oxymyoglobin and ferric myoglobin in meat surfaces. If only negligible amounts of reduced myoglobin are present in the sample, then the absorbance at 580 nm minus the absorbance at 630 nm is linearly related to the percentage of oxymyoglobin, or ferric myoglobin. The theoretical basis for this linear relationship is outlined. A drawback of the method is that the difference in absorbance (A580 ‐ A632) is dependent on the myoglobin concentration in the meat sample. Nevertheless, the method is very convenient for comparing the pigment composition of meat samples with similar myoglobin contents and for following the course of pigment changes in a single meat sample.