|Van Laack Riette|
Submitted to: Journal of Meat Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/23/1995
Publication Date: N/A
Citation: N/A Interpretive Summary: Fresh pork should be reddish-pink in color. A light pale color may indicate a quality defect known as PSE (pale soft exudative). PSE pork is pale, forms a large amount of purge during storage and has an undesirable sensory quality resulting from excessive protein denaturation. A dark color may indicate a high pH which makes the meat prone to spoilage. Thus, ,packers will select against either pale or dark pork. However, variation in color may also be the consequence of differences in pigment concentration. Several methods are available for measuring total pigment levels in meat. Often these methods have not been tested on their ability to detect differences in pigment concentration in meat with quality defects. It was hypothesized that protein denaturation may affect the efficiency of pigment extraction, i.e., PSE meat lower pigment values. We investigated the effect of protein denaturation and ultimate pH on the values obtained with different procedures for pigment determination. In experiment 1, protein denaturation did not affect the pigment values. However, all methods yielded different absolute values. In experiment 2, samples identified as either PSE, RSE (red soft exudative), RFN (red firm non-exudative) and DFD (dark firm dry) based upon drip losses and color L-values, were analyzed for pigment concentration using various procedures. The procedures yielded different absolute values. Moreover, depending on the method, the pigment concentration of meat from these four quality groups was either similar or significantly different. It is concluded that the lower pigment concentration reported for PSE pork may be due to the method used. All methods substantiate that DFD pork contains more pigment than pork from any of the other quality groups.
Technical Abstract: Three methods accepted for measuring pigment concentration in meat are: (1) alkaline haematin method (extraction in 0.05 M phosphate pH 7.4, 0.005 percent Triton, reaction with 5.0 M NaOH), (2) haematin-chloride method (extraction in acetone/hydrochloric acid), and (3) Nit409 method (extraction in 0.05 M phosphate pH 6.5, oxidation with 65 mM sodium nitrite, measurement of absorbance at 409 nm). Pigment concentration of pork with known quality defects was evaluated and compared for each method. In experiment 1, protein denaturation (induced by post-mortem incubation at 5-35 deg C) did not affect the pigment values. However, all methods yielded different absolute pigment values. When using the various procedures on a myoglobin standard, the alkaline haematin method and haematin-chloride method yielded similar results. The higher values obtained with the Nit409 method seem to be due to the molar extinction coefficient; according to our results this coefficient should be 145 mM. In experiment 2, loin samples identified as either PSE (Pale Soft Exudative), RSE (Red Soft Exudative), RFN (Red Firm Non-exudative) and DFD (Dark Firm Dry) based upon drip losses, L-values and ultimate pH, were analyzed for pigment concentration. The methods yielded different absolute pigment values. Moreover, depending on the method, the pigment concentration of meat from these four quality groups was either similar or significantly different. It is concluded that the lower pigment concentration reported for PSE pork may be due to the method used.