Effect of modified atmosphere packaging and potassium lactate injection- enhancement on beef steak surface redness

Our objective was to assess the effects of lactate enhancement in combination with different packaging systems (vacuum; high-oxygen, 80% O2 + 20% CO2; or 0.4% CO, 30% CO2 + 69.4% N2) on beef Longissimus lumborum and Psoas major steak redness. Subprimals (n = 16) were divided in half and randomly assigned to 1 of 4 injection treatments (non-injected control, water-injected control, 1.25% lactate, and 2.5% lactate in the finished product; pumped to 110%). Muscles were cut into steaks, each of which was assigned to 1 of 6 packaging x storage time (5 or 9 days at 1°C) combinations. Initial a* values also were measured prior to packaging and storage. On days 5 and 9 of storage, surface a* values were measured immediately after each steak was removed from its respective package. Lactate increased the redness of steaks packaged in highoxygen, but not steaks in vacuum or CO. Compared with the Psoas, steaks from the Longissimus had greater a* values in high-oxygen packaging. However, CO packaging resulted in greater a* values for the Psoas. Regardless of muscle type, CO packaging improved color stability compared with high-oxygen packaging. Introduction Myoglobin can exist in 4 redox states: deoxymyoglobin, oxymyoglobin, carboxymyoglobin, and metmyoglobin (Mancini & Hunt, 2005). Central packaging of case-ready meat products can increase color life via the use of both modified atmosphere packaging and injection-enhancement technologies. In particular, the use of carbon monoxide (CO) in packaging has become increasingly relevant for the US meat industry since its approval for use at a level of 0.4% in red meat modified atmosphere packaging systems. In addition, lactate is a commonly used injection-enhancement ingredient that stabilizes the color of beef products by minimizing surface discoloration during retail storage and display (Kim et al., 2006; Knock et al., 2006; Seyfert et al., 2007). Carbon monoxide (CO) binds to myoglobin and forms a bright cherry-red color (carboxymyoglobin), resulting in significant improvements in beef color stability (Jayasingh et al., 2001; Hunt et al., 2004; John et al., 2005). The ability of carbon monoxide to produce a bright cherry-red color may further enhance lactate’s color stabilizing effect. Research has evaluated the effects of lactate and carbon monoxide separately. However, published results from experiments combining both CO packaging and lactate are limited. Therefore, the objective of this study was to assess the effects of lactate enhancement in combination with different packaging systems (vacuum; highoxygen, 80% O2 + 20% CO2; or 0.4% CO, 30% CO2 + 69.4% N2) on beef Longissimus lumborum and Psoas major steak redness. Materials and methods Sixteen USDA Select beef strip loins (Longissimus lumborum) and tenderloins (Psoas major) were divided into two equal-length sections, and 1 of 4 injection treatments (1 = non-enhanced control; 2 = distilled water-enhanced positive control; 3 = 1.25% lactate; and 4 = 2.5% lactate) was assigned randomly to each section within a muscle. Positive controls and lactate-enhanced sections were pumped to 110% of green weight using a multi-needle injector with either distilled water or a solution containing water and potassium lactate, respectively. Finished product lactate concentration was either 1.25 or 2.5%. From each section, seven 2.54-cm thick steaks were cut and one steak from each section was assigned to d 0 redness analyses (no packaging or storage time). The fresh-cut surface of each d 0 steak was scanned 30 min after fabrication (bloom at 1 °C). The remaining 6 steaks were individually packaged in either vacuum, high-oxygen (80% O2 + 20% CO2), or 0.4% CO (0.4% CO + 30% CO2+ 69.6% N2) and were stored at 1 °C prior to color analyses. On d 5 and 9 of storage, redness on the surface was measured immediately after each steak was removed from its respective packaging using a HunterLab MiniScan XE Plus spectrophotometer (Model 45/0 LAV, 2.54-