The Use of Reflectance Spectrophotometry for the Assay of Raw Meat Pigments

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Abstract
SUMMARY: The literature on reflectance spectrophotometry, as it applies to meat pigments, is critically reviewed, and improved methods are suggested for determination of total pigments and of the percent metmyoglobin from reflectance data on raw meat. The suggested method for total pigment was based on reflectivity of the meat samples at 525 mμ, the isobestic point for myoglobin, oxymyoglobin, and metmyoglobin. The reflectivity data, when calculated as the corresponding ratios of the absorption coefficient K to the scattering coefficient S were linearly related to total pigment extract from the meat with acidified acetone. K/S values of pigment‐free (peroxide‐treated) samples were obtained as a base line. Lowering the pH of the meat decreased the K/S value. This was attributed to changes in texture which increased S. Metmyoglobin was determined from the ratio K/S 572 mp/K/S 525 mμ. Limiting values for the ratio were established for meat containing 100% and 0% metmyoglobin, and a linear relation was assumed between the ratios and intermediate amounts of metmyoglobin.