American Meat Science Association (AMSA).

Two procedures based on reflectance (R) measurements to calculate the proportions of deoxymyoglobin (DMb), oxymyoglobin (OMb) and metmyoglobin (MMb) in meat are recommended by the American Meat Science Association (AMSA). One uses the K/S ratios (K and S are the absorption and scattering coefficients) and the other method (Krzywicki 1979) uses the reflex attenuance A = log (1/R). Both methods were compared in: a) synthetic sets of two pigment mixtures and b) 15 samples of beef Longissimus Lumborum measured after 24h, 4 and 7days of exposure to air. It was found that K/S and Krzywicki methods gave different values of pigment proportions. However both methods exhibited a high linear correlation (R(2) = 0.8733 in DMb, R(2) = 0.9771 in OMb and R(2) = 0.9390 in MMb, p < 0.0001). This makes them equivalent for statistical analysis based on differences in pigment proportions.

American Meat Science Association News

American Meat Science Association News

ObjectivesMetmyoglobin reducing activity (MRA) is an inherent muscle biochemical property that can influence color stability. Hence, MRA is used in color research to better understand meat color changes. A greater postmortem muscle pH can affect inherent biochemical properties, including the conventional methodologies to determine MRA. The MRA methodology described in the American Meat Science Association Color Guide utilize changes in nitric oxide induced-metmyoglobin level pre- and post-incubation. However, a greater muscle pH can limit initial metmyoglobin formation. Hence, the methodology discussed in the AMSA color guide may not provide accurate results. Therefore, the objectives of this research were to compare different conditions to induce initial metmyoglobin formation.Materials and MethodsIn the first objective, normal-pH and dark-cutting steaks were dipped in 0.3%s (level recommended in the AMSA color guide) and 1% nitrite solution to induce metmyoglobin formation. Metmyoglobin formed steaks were blotted dry, vacuum packaged, and incubated at 30°C to induce metmyoglobin reduction. In the second experiment, 1% ferricyanide solution was used as an oxidizing agent. The methodology used in objective 1 was used to measure MRA. The experiments were replicated three times and the data were analyzed using the Mixed Procedure of SAS.ResultsThere was no effect (P &gt; 0.05) of nitrite concentration on MRA of dark-cutting beef. However, when 1% ferricyanide was used as an oxidizing agent, initial metmyoglobin was more (P &lt; 0.05) in dark-cutting beef compared with 0.3% sodium nitrite solution.ConclusionThe results suggest that the use of a strong oxidizing agent can impart more metmyoglobin formation in high-pH/dark-cutting beef.